Package the Linux desktop head as an RPM, and publish a nightly one

The third desktop platform shipped as nothing: a checkout somebody built.
VelopackUpdateChannel already named the two platforms it serves rather than
negating the one it does not, so that a Linux package would be an addition
there rather than something that had silently half-happened. This is it, and
it is deliberately not a Velopack channel.

There is no updater in the package at all. On this platform dnf is already an
updater the user trusts, audits and controls, and a second one answering to
this project instead is the capability ADR 0013 rule 4 spends a page keeping
unsettable. The cost is real and is written down rather than glossed: nothing
tells a Linux user that a newer build exists, because there is no repository
to tell them.

Rule 3 is untouched. The build job packages the release-shaped RPM on every
main build and every tag and uploads nothing, exactly as it does for Windows
and macOS; the desktop job packages the nightly-shaped one and puts it on the
rolling nightly-desktop release beside the Windows feed. Two RPMs with
different names owning different paths cannot replace one another, so rule 9's
separations come almost free here — the profile split still belongs to the
build, through DodoChannel.

vpk verifies that what it packs actually calls VelopackApp.Build().Run(), and
nothing here does that for us, so scripts/ci-linux-rpm.sh makes its own
assertions: it asks the finished package what it requires, what it provides,
what it holds and what modes those carry. Two of those checks exist because
the first realistic payload tripped them.

  - .NET's libmscordbi.so links libmscordaccore.so. With bundled provides
    excluded — which they must be, or this package would advertise libcoreclr
    to the whole system — that produced a dependency no host on earth can
    satisfy. The requires exclusion is computed from the payload rather than
    listed, because a list of Microsoft's internal file names goes stale in
    the direction that yields an uninstallable package.

  - cp -a inherits the publish directory's modes, and off the wrong filesystem
    that meant a world-writable /opt/DodoSSH: any local account able to
    replace the SSH client every other account runs. For an application
    holding a team's credentials in plaintext that is the trust model walked
    around rather than attacked. Every mode is now set absolutely.

Verified as far as a runner can: both packages install side by side on Fedora
44, resolve webkit2gtk4.1 2.52.5 — the backend MainWindow records as measured
— keep separate launchers, icons and profiles, and dnf remove takes one tree
and leaves the other. 0.0.1~alpha.0.143 sorts below both 0.0.1 and the next
height. What no runner can answer is Phase 19, which is new and unwalked.

RHEL 9 is deliberately not claimed. It ships WebKitGTK's 4.0 line under
libwebkit2gtk-4.0.so.37, and an or-branch for it was written and then removed:
nobody has run the head there, and dnf refusing with "nothing provides
libwebkit2gtk-4.1.so.0" is a better answer than an install that draws a blank
terminal. Same sentence, and the same reason, as the missing Intel Mac.

x86_64 only, for that reason and not a different one.

.gitattributes

@@ -20,8 +20,11 @@
 *.sql       text
 
 # Files that must keep LF regardless of platform — shell scripts run in Linux
-# containers, and Dockerfiles are read by a Linux daemon.
+# containers, Dockerfiles are read by a Linux daemon, and an RPM spec is a shell
+# script in disguise: rpmbuild feeds its %install section to /bin/sh, where a
+# carriage return at the end of a line is an argument rather than nothing.
 *.sh          text eol=lf
+*.spec        text eol=lf
 Dockerfile    text eol=lf
 *.Dockerfile  text eol=lf
 Caddyfile     text eol=lf

.github/workflows/ci.yml

@@ -462,6 +462,55 @@ jobs:
 
           echo "Bundled DodoSSH ${{ steps.winpack.outputs.packVersion }} for osx-arm64."
 
+      # ◆ AND THE THIRD DESKTOP PLATFORM, WHICH IS THE ONE THIS RUNNER ACTUALLY IS.
+      #
+      # Same argument as the two steps above and with none of their cross-compiling: this job runs on
+      # Linux, so the linux-x64 publish here is a native one. What it proves that the others cannot is
+      # the linux-x64 restore graph — libsodium, SkiaSharp and HarfBuzzSharp all ship native assets per
+      # RID, and a package that resolves for win-x64 and has no linux-x64 asset fails here.
+      #
+      # The runner is still Alpine and the package targets glibc distributions, which is fine and is not
+      # glossed over: scripts/ci-linux-rpm.sh explains why rpmbuild composing an RPM for one libc on a
+      # host running another is correct rather than lucky.
+      #
+      # ◆ IT IS ALSO WHERE THE PACKAGING ITSELF IS PROVED, WHICH ON THIS PLATFORM IS NOT A FORMALITY.
+      #
+      # The Windows and macOS steps hand a directory to vpk and vpk decides what the package needs.
+      # There is no vpk here — Velopack's Linux target is an AppImage and this is a distribution
+      # package, updated by dnf rather than by the application — so the dependency metadata is
+      # generated by rpm from the published tree, and scripts/ci-linux-rpm.sh interrogates the result
+      # rather than trusting an exit code. Every check in there is a way a package can be built
+      # successfully and then refuse to install on every host in the world; one of them was written
+      # because .NET's own libmscordbi.so links libmscordaccore.so, which is exactly that.
+      #
+      # Release-shaped rather than nightly-shaped — package name dodossh, tree at /opt/DodoSSH — so
+      # that what is proved on every main build is the packaging the release channel would use. The
+      # desktop job below builds the nightly-shaped one and is the only job that publishes either.
+      #
+      # ◆ NOTHING IS UPLOADED, FOR THE REASON THE WINDOWS STEP GIVES.
+      #
+      # RUNNER_TEMP, dying with the job. An RPM is if anything the easiest of the three to pass on
+      # casually — one file, no installer to click through, `dnf install` and done — which is a reason
+      # to keep it off a downloads page rather than a reason to put it on one. ADR 0013 rule 3.
+      - name: publish and package the linux desktop client
+        if: github.event_name != 'pull_request'
+        run: |
+          set -euo pipefail
+
+          # RestoreLockedMode=false for the RID, exactly as the two publishes above do — see the long
+          # note on the win-x64 one. This checkout is thrown away, so the lock files it rewrites go
+          # nowhere.
+          dotnet publish src/DodoSSH.Client.App/DodoSSH.Client.App.csproj \
+            --configuration Release --runtime linux-x64 --self-contained true \
+            -p:RestoreLockedMode=false \
+            --output "$RUNNER_TEMP/linux-x64"
+
+          scripts/ci-linux-rpm.sh \
+            --payload "$RUNNER_TEMP/linux-x64" \
+            --version '${{ steps.winpack.outputs.packVersion }}' \
+            --channel release \
+            --out "$RUNNER_TEMP/linux-rpm"
+
       # This includes the end-to-end suite, which starts PostgreSQL, Keycloak and an OpenSSH
       # server through Testcontainers and runs the API as a child process — so it needs a
       # Docker daemon and gets one here. That is why the tests run on ubuntu rather than
@@ -1048,6 +1097,45 @@ jobs:
 
           ls -la "$RUNNER_TEMP/nightly-releases"
 
+      # ◆ AND THE LINUX NIGHTLY, WHICH IS A PACKAGE RATHER THAN A FEED.
+      #
+      # Everything above this step is Velopack: an installer, an index file and a client that polls it.
+      # This one is an RPM, and the difference is not a gap in the work. VelopackUpdateChannel refuses
+      # every platform that is not Windows or macOS — deliberately, and its comment says why — so a
+      # Linux build has no self-updater to give a channel to. What it has instead is dnf, which is a
+      # mechanism the user already trusts and already controls, and build/linux/dodossh.spec argues
+      # that at length.
+      #
+      # So there is no rolling *feed* here, only a rolling *file*: the newest nightly RPM sits on the
+      # same release as the Windows nightly and somebody who wants it downloads it. That is a worse
+      # deal than the Windows nightly gets and it is the honest one — the alternative is a package
+      # repository, which is a deployment this project does not have.
+      #
+      # DodoChannel=nightly for the same reason the win-x64 publish above sets it: it is what
+      # ClientPaths reads to suffix the profile directory, so the nightly RPM and a release RPM
+      # installed beside it share no cache, no outbox and no device key. The package name, the tree
+      # under /opt and the desktop entry are the packaging half of that separation and are the
+      # script's `--channel nightly` — see the note there for why it is four things and not one.
+      - name: publish and package the linux nightly
+        id: linuxpack
+        env:
+          VERSION: ${{ steps.version.outputs.version }}
+        run: |
+          set -euo pipefail
+
+          dotnet publish src/DodoSSH.Client.App/DodoSSH.Client.App.csproj \
+            --configuration Release --runtime linux-x64 --self-contained true \
+            -p:RestoreLockedMode=false \
+            -p:DodoChannel=nightly \
+            -p:MinVerVersionOverride="$VERSION" \
+            --output "$RUNNER_TEMP/nightly-linux-x64"
+
+          scripts/ci-linux-rpm.sh \
+            --payload "$RUNNER_TEMP/nightly-linux-x64" \
+            --version "$VERSION" \
+            --channel nightly \
+            --out "$RUNNER_TEMP/nightly-rpm"
+
       # ◆ PUBLISHING IT, AND WHAT THAT CAPABILITY IS.
       #
       # Whoever can write a release here can put a build on every nightly desktop, because Velopack fetches
@@ -1145,7 +1233,45 @@ jobs:
             fi
           done
 
-          echo "Published nightly desktop $VERSION as $TAG"
+          # ◆ THE RPM GOES ONTO THE RELEASE vpk JUST MADE, RATHER THAN ONTO ONE OF ITS OWN.
+          #
+          # One rolling release carrying both heads, because they are one nightly: the same commit,
+          # the same version, and one page a person looks at to find out what is on main. A second tag
+          # would double the delete-and-recreate dance this step already does, and would let the two
+          # drift apart on a run where one of them failed.
+          #
+          # It has to happen here, after `vpk upload`, and not in a step before it. vpk deletes and
+          # recreates this release, so an RPM uploaded first would be attached to something that no
+          # longer exists by the time the job ends — silently, because the delete succeeds.
+          #
+          # curl rather than vpk, unlike the assets above, for the reason the android job gives about
+          # its APK: this is one file the release simply carries. There is no index to write and no
+          # format that belongs to a tool.
+          release="$(printf '%s' "$published" | release_id)"
+          if [ -z "$release" ]; then
+            echo "The release was published and its id could not be read back:" >&2
+            printf '%s\n' "$published" >&2
+            exit 1
+          fi
+
+          rpm='${{ steps.linuxpack.outputs.rpm }}'
+          rpmName='${{ steps.linuxpack.outputs.rpmName }}'
+          echo "Uploading $rpmName ($(wc -c < "$rpm") bytes)"
+          curl -fsS -X POST -H "$auth" \
+            -F "attachment=@$rpm" \
+            "$api/releases/$release/assets?name=$rpmName" >/dev/null
+
+          # Asked for back, exactly as the Velopack assets above are and for the same history: the
+          # android job once created a release, uploaded nothing, and reported success for every
+          # upload it never made.
+          withRpm="$(curl -fsS -H "$auth" "$api/releases/$release")"
+          if ! printf '%s' "$withRpm" | grep -qF "\"name\":\"$rpmName\""; then
+            echo "The release was created but $rpmName is not on it:" >&2
+            printf '%s\n' "$withRpm" >&2
+            exit 1
+          fi
+
+          echo "Published nightly desktop $VERSION as $TAG, with $rpmName"
 
   image:
     name: api image

README.md

@@ -177,6 +177,43 @@ passphrase screen, always. The application lives at `/Applications/DodoSSH.Deskt
 at `~/Library/Application Support/DodoSSH`, which are deliberately two different places so that removing the
 first never touches the second.
 
+## Installing on Linux
+
+An `.rpm` for x86_64, and the one platform where you get it from `main` rather than from a release — see
+[the nightly build](#the-nightly-desktop-build) below, which is where the Linux package is published today.
+
+```bash
+sudo dnf install ./dodossh-nightly-*.x86_64.rpm
+```
+
+Everything above about where a client may come from applies unchanged. Four things differ, and the first
+two are the ones to read before installing.
+
+**There is no self-updater, and that is the design rather than a gap.** The Windows and macOS builds carry
+Velopack and replace themselves; this one carries nothing of the sort and never contacts an update service.
+On Linux the package manager is already an updater the person running it trusts, audits and controls, and
+adding a second one that answers somewhere else would be handing back exactly the capability
+[ADR 0013](docs/adr/0013-desktop-distribution-and-updates.md) rule 4 spends a page keeping out of reach.
+The cost is real and worth stating plainly: this project publishes no package repository, so nothing tells
+you when a newer build exists. You install the next one the way you installed this one.
+
+**Your passphrase is asked for every time, because there is no hardware key store here.** Windows has a TPM
+behind a consent dialog and a Mac has the Secure Enclave behind Touch ID; the Linux head has neither wired
+up, so the "unlock without the passphrase" path is simply not offered — the application knows it has no
+store and does not pretend otherwise. See
+[docs/unlocking-without-the-passphrase.md](docs/unlocking-without-the-passphrase.md).
+
+**It needs WebKitGTK, because the terminal is a WebView.** Specifically `webkit2gtk4.1`, which `dnf` pulls
+in for you. Fedora 44 is the distribution the head has actually been run on. RHEL 9 and its rebuilds ship
+the older 4.0 API line under a different library name and the package deliberately does not claim them —
+`dnf` will refuse with *nothing provides libwebkit2gtk-4.1.so.0*, which is a better answer than installing
+and drawing a blank terminal. This project does not ship desktop builds nobody has run, on any platform.
+
+**Where things go.** The application at `/opt/DodoSSH`, launched as `dodossh` or from your menu; your vault
+cache at `$XDG_DATA_HOME/dodossh`, usually `~/.local/share/dodossh`. Two different places on purpose:
+`dnf remove` takes the first and never touches the second, so reinstalling asks for your passphrase rather
+than starting over. Use **Sign out** inside the application to make the machine genuinely forget.
+
 Cutting a release is `scripts/release-windows.ps1`, run by a person on a Windows machine, and
 `scripts/release-macos.sh` on a Mac. Deliberately not a CI job; ADR 0013 decision 3 explains why, and it is
 not only that the runners are Linux.
@@ -189,6 +226,18 @@ Nightly*, its own install directory, and its own profile at `%LOCALAPPDATA%\Dodo
 costs nothing you are relying on. It signs in separately and appears to your account as a new device,
 because it genuinely is a second installation.
 
+**The Linux `.rpm` is on the same release**, built from the same commit and versioned the same way, as
+`dodossh-nightly`. It installs beside a release package for the same reasons and by the same four
+separations — a different package name, a tree at `/opt/DodoSSH.Nightly`, a `dodossh-nightly` launcher with
+its own menu entry, and a profile at `~/.local/share/dodossh.nightly`. Two RPMs owning different paths
+cannot replace one another, so `dnf` will keep both rather than treating one as an upgrade of the other.
+
+It is the only Linux package this project publishes at all today: there is no `v*`-tagged Linux release
+yet, because no person has walked a Linux build through
+[docs/manual-checks.md](docs/manual-checks.md). What CI proves on every push to `main` is that the release
+package still *builds* — the same arrangement Windows and macOS have had since the beginning, where the
+package is built on every commit and uploaded nowhere.
+
 **Installing it means trusting everyone who can write a release on this repository, including CI.** The
 updater applies what the feed serves without verifying a signature, so anyone who can change a workflow
 file here can put a build on every nightly machine. That is an acceptable trade for a build you are trying
@@ -920,10 +969,21 @@ keychain plus a terminal — and the spike that gates all of it.
   [ADR 0013](docs/adr/0013-desktop-distribution-and-updates.md) decision 10 and
   [Installing on macOS](#installing-on-macos).
 
+  **The Linux half is a package rather than an updater.** An `.rpm` for x86_64, built and checked on every
+  push to `main` and published to the nightly release, installing to `/opt` with a menu entry and a `dodossh`
+  launcher. It carries no self-updater at all and contacts no update service — on this platform `dnf` is
+  already an updater the user controls, and a second one answering somewhere else is the capability the
+  trust model exists to keep out of reach. It also has no hardware-backed device key store, so the
+  passphrase is asked for every unlock. See
+  [ADR 0013](docs/adr/0013-desktop-distribution-and-updates.md) decision 11 and
+  [Installing on Linux](#installing-on-linux).
+
   Still to do here: Windows signing (the first Windows release is unsigned, and the trigger for buying a
-  certificate is the first release aimed at strangers), macOS on Intel, Linux packaging, and Phase 18 of the
-  manual checks — the macOS build has never actually run, because there is no macOS runner in CI and
-  everything above is verified only as far as the bundle.
+  certificate is the first release aimed at strangers), macOS on Intel, a `v*`-tagged Linux release and a
+  package repository to serve it from, a Linux device key store, and Phases 18 and 19 of the manual
+  checks — neither the macOS nor the Linux build has been walked through by a person. There is no macOS
+  runner in CI at all, and the Linux package is verified only as far as what it *says* about itself: CI
+  builds it and interrogates its dependencies, its file list and its modes, and installs nothing.
 - **M5 — multi-provider OIDC**, identity key rotation, per-item content keys.
 
 ## Licence

build/linux/dodossh.spec

@@ -0,0 +1,294 @@
+# ==================================================================================================
+#  The Linux desktop head, as an RPM.
+#
+#  Built by scripts/ci-linux-rpm.sh, which is what supplies every dodo_* macro below and what checks
+#  the result. Nothing here is invoked by hand; `rpmbuild -bb` on this file with no --define set will
+#  fail on the Version line, which is the intended way round.
+#
+#  ◆ WHY THIS IS AN RPM AND NOT A VELOPACK RELEASE, WHICH IS THE FIRST QUESTION.
+#
+#  Both desktop platforms that ship today are Velopack: the client polls the project's forge, fetches
+#  a newer build and swaps itself over. ADR 0013 rule 4 is what makes that safe to hold — the feed
+#  address is a const, so no operator can answer "is there a newer version" on the user's behalf.
+#
+#  This package has no updater in it at all, and that is deliberate rather than unfinished.
+#  VelopackUpdateChannel.ForThisMachine already refuses every platform that is not Windows or macOS,
+#  and it says why in a comment worth not undoing: a client handed an UpdateManager pointed at a feed
+#  carrying nothing it can apply is a client that reports itself current forever. On Linux the
+#  package manager is the updater — `dnf upgrade` is a mechanism the user already trusts, already
+#  audits and already controls — so the honest thing is to be an ordinary package and let it do that,
+#  rather than to bolt on a second one that answers to a different authority.
+#
+#  The consequence to know: an installed RPM learns about a new version when its repository does, and
+#  this project publishes no repository yet. Somebody who downloaded the file installs the next one
+#  the same way.
+# ==================================================================================================
+
+# ◆ THE THREE THINGS THAT MUST BE TURNED OFF, AND WHAT EACH ONE WOULD DO.
+#
+# __os_install_post is the chain of brp-* scripts rpm runs over the buildroot: strip, strip-static,
+# compress, elfperms. Every one of them is wrong here. The payload is a published .NET tree whose
+# managed PDBs ADR 0013 rule 6 keeps on purpose — a stack with file names and line numbers is this
+# project's entire diagnostic channel — and brp-strip would take the native symbols with them for a
+# saving nobody asked for. It also runs the host's binutils over glibc binaries on a build host that
+# is musl, which is a class of breakage with no good failure message.
+#
+# debug_package would then try to build a -debuginfo subpackage out of what strip extracted, from
+# third-party binaries nobody here will ever step through.
+#
+# _build_id_links is the one that surprises people, because turning the other two off does not turn
+# it off: rpm still writes /usr/lib/.build-id/<xx>/<hash> symlinks for every ELF file in the payload.
+# For a bundled tree that means dozens of links in a system directory this package has no business
+# owning, and two files with the same build id — which a .NET publish does produce — make it a build
+# *warning* about duplicates rather than an error, so it goes unnoticed.
+%global __os_install_post %{nil}
+%global debug_package     %{nil}
+%global _build_id_links   none
+
+# ◆ AUTO-REQUIRES STAYS ON. AUTO-PROVIDES DOES NOT. THE ASYMMETRY IS THE WHOLE POINT.
+#
+# rpm's elfdeps reads DT_NEEDED and the symbol-version table out of every ELF file in the buildroot,
+# and the requires half of that is worth much more than a hand-written list: it produces
+# `libc.so.6(GLIBC_2.38)(64bit)` rather than `glibc`, so the package refuses to install on a host
+# whose glibc is too old instead of installing and dying at the first launch. A hand list cannot
+# express that and would go stale the first time a dependency changed underneath it.
+#
+# It reads ELF directly rather than by loading anything, so it does this correctly for x86_64 glibc
+# binaries on a musl build host — which is what lets this package be built on the same Alpine runner
+# as everything else in ci.yml.
+#
+# The provides half is the opposite. Everything under /opt here is a *bundled* copy: libSkiaSharp,
+# libcoreclr, libe_sqlite3 and the rest belong to this application and to nothing else. Left on,
+# this package would advertise `libcoreclr.so()(64bit)` to the whole system, and some other package's
+# dependency could then be satisfied by a private copy inside a directory `dnf remove dodossh` takes
+# away. Excluding the tree by path is the standard shape for that and costs nothing, because nothing
+# outside this package is meant to link against anything inside it.
+#
+# ◆ WHICH IS WHY THE REQUIRES SIDE NEEDS AN EXCLUSION TOO, AND WHY IT IS COMPUTED.
+#
+# The two halves are not independent. A bundled library with a DT_NEEDED on another bundled library
+# produces a requirement for a soname this package carries and — after the exclusion above — no
+# longer advertises, which no host on earth can satisfy. It is not hypothetical and it is not rare:
+# .NET's own libmscordbi.so links libmscordaccore.so, so the very first realistic payload this was
+# tried against produced a package `dnf install` refuses outright.
+#
+# dodo_bundled is the alternation of every lib*.so* filename in the payload, worked out by
+# scripts/ci-linux-rpm.sh from the tree it was handed rather than listed here. A list in this file
+# would be a list of Microsoft's and SkiaSharp's internal file names, kept in step by hand, and its
+# failure mode is the uninstallable package above.
+#
+# liblttng-ust is excluded on its own terms and not because it is bundled — it is not. It is what
+# libcoreclrtraceptprovider.so links, and that file exists so that CoreCLR can emit LTTng trace
+# events if a host has the tracing stack. Nothing here asks it to. The file is kept and the
+# requirement is dropped, which is the arrangement that works both ways round: where liblttng-ust is
+# present the dlopen succeeds and tracing is available, and where it is absent CoreCLR carries on, as
+# it does on every machine that runs a .NET application without it. Requiring it instead would put
+# the package out of reach on RHEL, where lttng-ust is in EPEL rather than in the base repositories —
+# an install failure on a supported distribution, in exchange for a tracing integration this
+# application does not use.
+#
+# scripts/ci-linux-rpm.sh checks the finished package against its own file list afterwards, because
+# an exclusion that silently stopped matching would put the uninstallable package back with no
+# warning anywhere.
+%global __provides_exclude_from ^/opt/.*$
+%global __requires_exclude      ^(liblttng-ust\.so|%{dodo_bundled})
+
+Name:           %{dodo_name}
+Version:        %{dodo_version}
+Release:        %{dodo_release}
+Summary:        SSH client with an end-to-end encrypted credential vault
+License:        MIT
+URL:            https://git.dodotech.cloud/DodoTech-Public/DodoSSH
+BuildArch:      x86_64
+
+# ◆ THE DEPENDENCIES elfdeps CANNOT SEE, WHICH ARE THE ONES THE PRODUCT IS MADE OF.
+#
+# Everything below is reached through dlopen, by a name composed at runtime, so it appears in no
+# DT_NEEDED entry anywhere in the payload. Left to the automatic scan the package would install
+# cleanly on a host with none of it and fail at the first window.
+#
+# GTK and WebKitGTK are the terminal. Avalonia.Controls.WebView P/Invokes a bare `libwebkit2gtk` and
+# a bare `libgtk` and resolves them itself, and MainWindow.OnTerminalEnvironmentRequested documents
+# the backend it was measured against: WebKitGTK 2.52.5 on Fedora 44, which is the 4.1 API line — the
+# assembly's one fully-spelled soname, libjavascriptcoregtk-4.1.so.0, is that line's other half.
+#
+# ◆ THE 4.0 LINE IS DELIBERATELY NOT CLAIMED, AND THE COST OF THAT IS KNOWN.
+#
+# The control's own diagnostic says "webkit2gtk 4.0+", so a dependency permitting either line is
+# tempting and was written first. RHEL 9 and its rebuilds are what it would buy: they ship
+# webkit2gtk3, which is the 4.0 API under the soname libwebkit2gtk-4.0.so.37 — not .so.0, which is
+# what makes this a thing to look up rather than guess. Requiring only 4.1 means `dnf install` on
+# AlmaLinux 9 refuses with "nothing provides libwebkit2gtk-4.1.so.0", by design.
+#
+# It is refused because nobody has run it. This project does not ship an Intel macOS package for the
+# same reason and says so in ADR 0013 decision 10 — the engineering is small and the verification is
+# the scarce thing — and an install that succeeds and then draws a blank terminal is a worse answer
+# than one that refuses in a sentence naming the missing library. The day somebody runs the head on
+# a 4.0 host, this becomes a rich `or` and a line in the README.
+#
+# libX11 is Avalonia's own backend, P/Invoked the same way. On Wayland this is satisfied by XWayland,
+# which every desktop shipping this package has.
+#
+# libicu is the one that looks removable and is not. DodoSSH.Client.App sets InvariantGlobalization
+# to false — deliberately, and the csproj says why: this process prints timestamps and host names to
+# a person who expects their own locale's conventions. A .NET process configured that way and given
+# no ICU does not degrade to invariant, it refuses to start. The bare package name is the Fedora and
+# RHEL spelling; it is the one name here that is a distribution's rather than a soname's, because ICU
+# bumps its soname on every release and pinning one would make this package expire.
+Requires:       libwebkit2gtk-4.1.so.0()(64bit)
+Requires:       libgtk-3.so.0()(64bit)
+Requires:       libgdk-3.so.0()(64bit)
+Requires:       libgio-2.0.so.0()(64bit)
+Requires:       libglib-2.0.so.0()(64bit)
+Requires:       libgobject-2.0.so.0()(64bit)
+Requires:       libX11.so.6()(64bit)
+Requires:       libicu
+
+# The size directories under /usr/share/icons/hicolor belong to hicolor-icon-theme and not to this
+# package, which is the right way round — every application drops icons into them. Depending on the
+# owner is how those directories come to exist at all on a minimal host, and how they get removed
+# again when the last thing using them goes.
+Requires:       hicolor-icon-theme
+
+%description
+DodoSSH is an SSH and SFTP client for teams whose credentials are shared and whose infrastructure is
+not. Hosts, keys and passphrases live in a vault that is encrypted on this machine and stays
+encrypted on the server, so the deployment holding a team's secrets can never read them.
+
+This package carries its own .NET runtime and is updated the way every other package on this system
+is; it contains no self-updater and contacts no update service.
+
+%install
+rm -rf %{buildroot}
+
+# ◆ /opt, AND NOT /usr/lib64/dodossh, WHICH IS THE MORE CONVENTIONAL PLACE.
+#
+# The Filesystem Hierarchy Standard reserves /opt for exactly this — an add-on package that arrives
+# as one self-contained tree — and that is what a published .NET application is: a runtime, thirty
+# managed assemblies and half a dozen native libraries that only make sense together and are only
+# ever loaded by each other. Scattering them into the system library directory would mix a bundled
+# libSkiaSharp in with the system's shared objects, which is the arrangement the provides exclusion
+# above exists to keep this package out of.
+#
+# The directory name carries the channel, so a release and a nightly are two trees rather than one
+# that overwrites the other. That is the same separation ADR 0013 rule 9 builds on Windows out of
+# pack ids, arrived at here for free: two RPMs with different names owning different paths cannot
+# replace one another, and dnf will say so rather than doing it. The profile directory is separated
+# by the build itself — DodoChannel=nightly is what ClientPaths reads to suffix it — so the two
+# installs share no state at all.
+mkdir -p %{buildroot}/opt/%{dodo_dir}
+cp -a %{dodo_payload}/. %{buildroot}/opt/%{dodo_dir}/
+
+# ◆ AND THE MODES ARE SET HERE RATHER THAN INHERITED, WHICH IS NOT TIDINESS.
+#
+# `cp -a` preserves what the publish directory happened to have, and what it happened to have is a
+# property of the filesystem it was written on rather than of anything decided here. rpmlint caught
+# the consequence on the first tree this was tried against: every file in the package was mode 777,
+# because the tree had come off a mount that reports everything that way.
+#
+# For this application that is not a lint warning, it is a hole. A world-writable /opt/DodoSSH lets
+# any local account replace the SSH client belonging to every other account on the machine — the
+# binary that holds a team's infrastructure credentials in plaintext while it runs, which is the
+# thing ADR 0001 spends its whole trust model on. Malware running as nobody-in-particular would not
+# need to attack the crypto; it would edit the client.
+#
+# Stated absolutely and in this order, so the answer does not depend on the publish at all:
+# directories and the things that are executed or loaded get 0755, and everything else — assemblies,
+# PDBs, the runtime config, the terminal's HTML and JavaScript — gets 0644. Owned by root, which is
+# rpm's default for a package that names no %attr user, and is what makes the modes mean anything.
+find %{buildroot}/opt/%{dodo_dir} -type d -exec chmod 0755 {} +
+find %{buildroot}/opt/%{dodo_dir} -type f -exec chmod 0644 {} +
+find %{buildroot}/opt/%{dodo_dir} -type f -name '*.so*' -exec chmod 0755 {} +
+
+# The two files a .NET publish means to be executed. createdump is the runtime's crash-dump helper
+# and is only present on some publishes, so it is conditional; the apphost never is, and the check
+# above this section has already refused a publish without one.
+chmod 0755 %{buildroot}/opt/%{dodo_dir}/DodoSSH
+[ -f %{buildroot}/opt/%{dodo_dir}/createdump ] && chmod 0755 %{buildroot}/opt/%{dodo_dir}/createdump
+true
+
+# The apphost is the thing to launch and every other file in the tree is loaded relative to it, so
+# what goes on PATH is a symlink rather than a copy or a wrapper script. .NET resolves its own
+# directory through /proc/self/exe, which follows the link, so a symlinked apphost finds its runtime
+# with no help — a wrapper exporting DOTNET_ROOT or cd-ing first would be solving a problem that
+# does not exist here, and would be one more file to keep in step with the layout.
+#
+# Relative — ../../opt from /usr/bin — rather than the absolute /opt path it resolves to. Both work
+# on a running system and only one works inside a chroot or an image being assembled somewhere other
+# than /, which is where absolute symlinks out of a package are checked and warned about.
+mkdir -p %{buildroot}%{_bindir}
+ln -s ../../opt/%{dodo_dir}/DodoSSH %{buildroot}%{_bindir}/%{dodo_bin}
+
+# ◆ THE DESKTOP ENTRY IS WRITTEN HERE RATHER THAN SHIPPED AS A SOURCE FILE.
+#
+# Three of its seven meaningful lines differ between the release and the nightly, and the two files
+# that would result are the kind of pair that drifts: somebody adds a MIME type to one of them and
+# nobody notices for a release. Composed from the same macros the rest of the layout uses, they
+# cannot.
+#
+# StartupWMClass is the line that is easy to leave out and visibly wrong without: Avalonia sets
+# WM_CLASS from the assembly name, which is DodoSSH for both channels, so without this a launched
+# window is a second, unlabelled icon in the dock beside the one that launched it. It is the assembly
+# name deliberately and not the package's binary name — the window does not know which package
+# started it.
+mkdir -p %{buildroot}%{_datadir}/applications
+cat > %{buildroot}%{_datadir}/applications/%{dodo_bin}.desktop <<DESKTOP
+[Desktop Entry]
+Type=Application
+Version=1.0
+Name=%{dodo_title}
+GenericName=SSH Client
+Comment=SSH and SFTP with an end-to-end encrypted credential vault
+Exec=%{dodo_bin}
+Icon=%{dodo_bin}
+Terminal=false
+StartupNotify=true
+StartupWMClass=DodoSSH
+Categories=Network;RemoteAccess;System;
+Keywords=SSH;SFTP;Terminal;Remote;Shell;
+DESKTOP
+
+# One file per size into the hicolor theme, named for the package so the two channels show different
+# entries rather than fighting over one path. The sizes are the ones the icon script draws and its
+# comment argues for; adding one there means adding it here.
+for size in 48 64 128 256; do
+    mkdir -p %{buildroot}%{_datadir}/icons/hicolor/${size}x${size}/apps
+    install -m 0644 %{dodo_icons}/dodossh-${size}.png \
+        %{buildroot}%{_datadir}/icons/hicolor/${size}x${size}/apps/%{dodo_bin}.png
+done
+
+# Installed rather than listed straight out of the source tree. `%license` is a %doc-style marker and
+# resolves its argument against the build directory, which this spec does not have — there is no
+# %prep and no %build, because the payload arrives already published. Putting the file where it
+# belongs first and marking the installed path second is the form that works with neither.
+mkdir -p %{buildroot}%{_licensedir}/%{name}
+install -m 0644 %{dodo_licence} %{buildroot}%{_licensedir}/%{name}/LICENSE
+
+# Modern rpm on Fedora fires file triggers that do both of these, so on the distribution this was
+# measured against they are redundant. They are here for the ones that do not, and every line ends in
+# `|| :` so that a host without the tool installed gets a package that installs rather than a
+# scriptlet failure at the end of a 130 MB transaction.
+%post
+/usr/bin/update-desktop-database %{_datadir}/applications &>/dev/null || :
+/usr/bin/gtk-update-icon-cache -qtf %{_datadir}/icons/hicolor &>/dev/null || :
+
+%postun
+/usr/bin/update-desktop-database %{_datadir}/applications &>/dev/null || :
+/usr/bin/gtk-update-icon-cache -qtf %{_datadir}/icons/hicolor &>/dev/null || :
+
+%files
+# The whole tree, owned by this package, which is what makes `dnf remove` take all of it. The user's
+# vault cache is not in here and is not touched by an uninstall — ClientPaths puts it under
+# $XDG_DATA_HOME, which is the Linux spelling of the same decision ADR 0013's consequences record for
+# Windows: the install moves, the profile does not, and an uninstall is not a sign-out.
+/opt/%{dodo_dir}
+%{_bindir}/%{dodo_bin}
+%{_datadir}/applications/%{dodo_bin}.desktop
+%{_datadir}/icons/hicolor/*/apps/%{dodo_bin}.png
+%license %{_licensedir}/%{name}/LICENSE
+
+%changelog
+# Deliberately empty. The changelog of record is the git history and the release notes on the forge,
+# and a %changelog generated per build from a version number carries no information that `rpm -q`
+# does not already answer — while a hand-written one is a third place a release has to remember to
+# edit. rpmlint says W: no-changelog and that warning is accepted.

docs/adr/0013-desktop-distribution-and-updates.md

@@ -316,6 +316,66 @@ preferences screen, which is the screen somebody reads when asked which nightly
 across the floor holds: heights rise within a floored version, and the first real tag moves past all of
 them. The release script gets no floor and must not have one; there, `0.0.0` should be refused.
 
+### 11. Linux is a third desktop platform, and it is a package rather than an updater
+
+The Linux head existed and shipped as nothing: a checkout somebody built. `VelopackUpdateChannel` already
+named the two platforms it serves rather than negating the one it does not, on the reasoning that "a future
+AppImage should be an addition here rather than a thing that silently already half-happened". This is that
+addition, and it is not an AppImage.
+
+**The package is an RPM and there is no updater in it.** That is the decision, and everything else follows
+from it. Velopack does have a Linux path, so the shape of decisions 1 through 9 could have been repeated a
+third time — one more channel, one more index, one more client polling the forge. It should not be, because
+this platform already has the mechanism that whole apparatus is a substitute for. `dnf` is an updater the
+user already trusts, already audits and already controls, and it updates the runtime's own dependencies
+besides. Adding a second one that answers to this project instead would be building the capability decision
+4 spends a page keeping unsettable, on the one platform where nobody had to.
+
+The honest cost, recorded because it is the part that will be argued with: **discovery is worse here than on
+either other desktop.** Windows and macOS clients learn about a new build within six hours without anybody
+deciding to look. A Linux user learns when their repository does, and this project publishes no repository,
+so today they learn when they next go and look. That is a real regression against the sharpest thing this
+ADR bought, accepted because the alternative regression — a second update path with a different authority
+behind it — is the one the trust model cannot afford. A package repository is the fix and is not built.
+
+**CI publishes it, and only to the nightly channel.** Rule 3 is untouched and applies with its full force:
+the token that writes a release is the capability to ship somebody a build, and it stays off runners. What
+changes is nothing, because rule 9 already established a channel CI may publish to and this is a second
+artefact on it. The release-shaped package is built on every `main` build and on every tag and uploaded
+nowhere, exactly as the Windows and macOS packages are, which proves the `linux-x64` restore graph and the
+packaging without putting an installer anybody has run in a place that invites passing it on.
+
+Note what CI's check is and is not. `vpk` verifies that the main executable actually calls
+`VelopackApp.Build().Run()` — a real assertion about the application, made for free by the packager. There
+is no equivalent here, so `scripts/ci-linux-rpm.sh` makes its own: it asks the finished package what it
+requires, what it provides, what files it holds and what modes they carry, and fails on each way a package
+can build cleanly and then be uninstallable or unsafe. Two of those checks exist because the first realistic
+payload tripped them — .NET's `libmscordbi.so` links `libmscordaccore.so`, which with bundled provides
+excluded produces a dependency no host can satisfy; and `cp -a` off the wrong filesystem produced a
+world-writable `/opt/DodoSSH`, which is a local privilege escalation against an application holding
+plaintext credentials.
+
+**The separations of rule 9 survive translation, and cost less here.** Two RPMs with different names owning
+different paths cannot replace one another and `dnf` says so, where on Windows the same property had to be
+built out of pack ids. The profile split is unchanged and still belongs to the build: `DodoChannel=nightly`
+is what `ClientPaths` reads, and the packaging must not answer that question a second time.
+
+**Two things this platform does not have, and they are stated rather than left to be discovered.** There is
+no hardware-backed device key store — `DesktopDeviceKeyStores` returns `UnavailableDeviceKeyStore`, so the
+passphrase is asked for at every unlock, where Windows has a TPM and a Mac has the Secure Enclave. And there
+is no signature on the package, which is not decision 8's "unsigned for now": nothing on this platform
+refuses or warns about an unsigned RPM, so there is no dialog to buy a certificate to remove. What stands in
+for one is the same thing that stands in for it on the forge — TLS, and a project that publishes from one
+address. An RPM repository would change that, because repository metadata is signed and a repository is a
+thing users add once and then trust; that is the point at which a key becomes necessary rather than optional,
+and it is the reason building one is a decision and not a chore.
+
+**x86_64 only, for decision 10's reason and not a different one.** aarch64 is one argument to the publish
+and one to the script. What is missing is somebody to run Phase 19 on such a machine, and this project does
+not ship desktop builds nobody has run. The same sentence rules out claiming RHEL 9, which ships WebKitGTK's
+4.0 API line under a soname the package deliberately does not accept: `dnf` refusing with *nothing provides
+libwebkit2gtk-4.1.so.0* is a better answer than an install that draws a blank terminal.
+
 ## Consequences
 
 **The desktop gets what ADR 0011 had to refuse the phone.** Discovery is still manual — somebody has to be
@@ -369,6 +429,10 @@ ADR 0011 changes.
   genuinely the nicest onboarding available and will be proposed again.
 - **Conditioning updates on `MinClientVersion`.** See decision 5. It would create the attack rather than
   inherit it.
+- **A Velopack channel for Linux.** The mechanism exists — Velopack builds an AppImage — and repeating
+  decisions 1 through 9 a third time would have been the consistent-looking move. Declined in decision 11
+  because this is the one desktop platform that already has an updater the user controls, and a second one
+  answering to this project is the capability decision 4 exists to make unsettable.
 - **Azure Trusted Signing**, for now, on custody grounds rather than on mechanics. See decision 8.
 - **A hand-edited version property.** Considered seriously against MinVer, and it loses on the thing that
   matters here: the tag is already the version of record for the container image, and two places to write

docs/manual-checks.md

@@ -2841,3 +2841,112 @@ Register a device, sync something, then remove the application.
 **Failure means:** an empty directory is the pack id having been changed to `DodoSSH`, which puts Velopack's
 install root on top of `ClientPaths.DataDirectory` and makes an uninstall delete a user's un-synced work.
 This is the single reason the bundle is named `DodoSSH.Desktop.app`.
+
+## Phase 19 — Installing the Linux client, and the things dnf does not check
+
+The Linux counterpart of phases 16 and 18, and the shortest of the three because the platform takes two of
+their questions off the table. There is no updater here, so nothing in this phase asks whether an update
+arrives; and there is no signing, because nothing on this platform refuses an unsigned package — a distinct
+statement from "unsigned is fine", and `build/linux/dodossh.spec` says what stands in for a signature: the
+package comes from the project's own forge over TLS and from nowhere else.
+
+What that leaves is the set nobody else can answer. **CI builds this package and installs nothing**, and
+every check in `scripts/ci-linux-rpm.sh` is a check on what the package *says* — its dependencies, its file
+list, its modes. None of them start the application, and the failures below are all of the shape "installs
+perfectly and then does not work".
+
+Needs a Fedora 44 machine or newer with a graphical session. Build the package first:
+
+```bash
+dotnet publish src/DodoSSH.Client.App/DodoSSH.Client.App.csproj \
+  --configuration Release --runtime linux-x64 --self-contained true \
+  -p:RestoreLockedMode=false --output /tmp/linux-x64
+scripts/ci-linux-rpm.sh --payload /tmp/linux-x64 --version 1.2.3 --out /tmp/rpm
+sudo dnf install /tmp/rpm/dodossh-1.2.3-1.x86_64.rpm
+```
+
+### 19.1 It launches from the menu, and not only from a shell · **do this one first**
+
+Log out and back in, or wait for the desktop to notice the new `.desktop` file, then start DodoSSH from the
+applications menu rather than from a terminal.
+
+**Pass:** the window opens, and the running application's icon in the dock or task list is the same entry
+that launched it — one icon, not two.
+
+**Failure means:** a second unlabelled icon appearing beside the launcher is `StartupWMClass` not matching
+what Avalonia sets `WM_CLASS` to. The spec sets it to `DodoSSH`, which is the assembly name and is the same
+for both channels; if Avalonia's answer has changed, `xprop WM_CLASS` on the window is what to compare
+against. Nothing at all in the menu is the desktop database not having been rebuilt — `%post` runs
+`update-desktop-database` and swallows its failure on purpose, so try it by hand before concluding anything.
+
+### 19.2 The terminal draws, which is the WebKitGTK question
+
+Connect to a host and use the shell: type, run something that scrolls, resize the window.
+
+**Pass:** the terminal attaches within a second or two and behaves as it does on Windows.
+
+**Failure means:** **a blank pane where everything else works is the known one**, and it is the reason
+`MainWindow.OnTerminalEnvironmentRequested` exists — the GTK WebView adapter in its default mode can only
+open a window of its own, so a control asked to host it in place has nothing to draw. If that method has
+stopped setting `ExperimentalOffscreen`, or the vendor has withdrawn the flag, this is what it looks like.
+A pane that reports a renderer timeout instead is the loopback WebSocket rather than the backend.
+
+### 19.3 The icon is the mark, at the sizes the desktop actually asks for
+
+Look at it in the applications menu, in the dock, and in the window switcher.
+
+**Pass:** the accent tile and the `>_` mark, filling its square, legible at the small end.
+
+**Failure means:** a generic icon is `Icon=` in the desktop entry not matching an installed file name — both
+are the package's binary name, so they can only disagree if one was edited. A blurry small icon is the
+48-pixel file missing and the 256 being scaled down; `dodossh-icon.ps1` draws four sizes and the spec
+installs four.
+
+### 19.4 The passphrase is asked for, and no device key is offered
+
+Open the security settings page.
+
+**Pass:** registering a device key is **not** offered, and unlocking asks for the passphrase every time.
+
+**Failure means:** being offered it is `DesktopDeviceKeyStores.ForThisMachine` having returned something
+other than `UnavailableDeviceKeyStore` on a platform with nothing to back it. Accepting the offer would put
+a wrap on the server that nothing can ever open.
+
+### 19.5 The nightly installs beside the release rather than over it
+
+With the release package installed, install the nightly one too.
+
+**Pass:** `dnf` installs it as a second package rather than as an upgrade. Both entries appear in the menu,
+named *DodoSSH* and *DodoSSH Nightly*. Both run at once. Signing into the nightly asks for the passphrase
+again and appears on the account as a separate device.
+
+**Failure means:** `dnf` offering to *upgrade* rather than install is the two packages sharing a name. A
+nightly that opens the release's vault already unlocked is the profile separation gone — that comes from
+`DodoChannel=nightly` reaching `ClientPaths`, not from the packaging, so check
+`~/.local/share/dodossh.nightly` exists rather than looking at the spec.
+
+### 19.6 Nothing in the installed tree is writable by anyone but root
+
+```bash
+find /opt/DodoSSH ! -user root -o -perm -o+w
+```
+
+**Pass:** no output.
+
+**Failure means:** any line here is a local account being able to replace the SSH client every other account
+on the machine runs, which for an application holding a team's credentials in plaintext is the whole trust
+model walked around rather than attacked. `ci-linux-rpm.sh` refuses to produce such a package and the spec
+sets every mode absolutely, so a hit here means one of those two was changed — it cannot arrive by accident
+from a publish directory.
+
+### 19.7 Removing it leaves the vault, and leaves the other channel alone
+
+Register a device, sync something, then `sudo dnf remove dodossh`.
+
+**Pass:** `~/.local/share/dodossh` still holds the cache and the outbox. `/opt/DodoSSH` is gone entirely.
+`/opt/DodoSSH.Nightly` and its menu entry are untouched.
+
+**Failure means:** a missing cache is `ClientPaths` having been pointed somewhere under `/opt`, which would
+make an uninstall delete a user's un-synced work — the Linux spelling of the mistake ADR 0013 decision 2
+exists to prevent. Files left behind under `/opt/DodoSSH` are files the package did not own, which means
+something wrote into the install directory at runtime and would survive a reinstall.

scripts/ci-linux-rpm.sh

@@ -0,0 +1,320 @@
+#!/usr/bin/env bash
+#
+# Turns a published linux-x64 tree into an RPM, and then checks the RPM rather than the exit code.
+#
+# Called from two jobs in .github/workflows/ci.yml and written once for the reason the four copies of
+# "ensure node and git" in that file are not: those cannot be factored out — a composite action would
+# need the checkout it exists to unblock — and this can. The build job packages the release-shaped
+# RPM and throws it away, exactly as it does for Windows and macOS; the desktop job packages the
+# nightly-shaped one and publishes it. Everything that differs between those two is an argument.
+#
+# It is also runnable at a desk, which is the point of it being a script:
+#
+#     dotnet publish src/DodoSSH.Client.App/DodoSSH.Client.App.csproj \
+#       --configuration Release --runtime linux-x64 --self-contained true \
+#       -p:RestoreLockedMode=false --output /tmp/linux-x64
+#     scripts/ci-linux-rpm.sh --payload /tmp/linux-x64 --version 1.2.3 --out /tmp/rpm
+#
+# Nothing here holds a secret and nothing here uploads anything. Publishing is the calling job's, and
+# ADR 0013 rule 3 is what decides which channel may do it.
+
+set -euo pipefail
+
+repo_root="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+
+payload=""
+version=""
+channel="release"
+out=""
+
+while [ $# -gt 0 ]; do
+    case "$1" in
+        --payload) payload="$2"; shift 2 ;;
+        --version) version="$2"; shift 2 ;;
+        --channel) channel="$2"; shift 2 ;;
+        --out)     out="$2";     shift 2 ;;
+        *) echo "Unknown argument: $1" >&2; exit 2 ;;
+    esac
+done
+
+for required in payload version out; do
+    if [ -z "${!required}" ]; then
+        echo "--$required is required." >&2
+        exit 2
+    fi
+done
+
+case "$channel" in
+    release|nightly) ;;
+    *) echo "--channel must be release or nightly, not '$channel'." >&2; exit 2 ;;
+esac
+
+# The apphost, named rather than globbed. A publish that produced no apphost at all would otherwise
+# package happily into an RPM whose /usr/bin symlink points at nothing, and the first thing anybody
+# would learn about it is a shell saying "No such file or directory" for a file that is right there.
+if [ ! -s "$payload/DodoSSH" ]; then
+    echo "There is no apphost at $payload/DodoSSH, so there is nothing to package." >&2
+    ls -la "$payload" >&2 || true
+    exit 1
+fi
+
+# ◆ THE FOUR THINGS THAT DIFFER BETWEEN THE CHANNELS, AND WHY IT IS FOUR AND NOT ONE.
+#
+# This is ADR 0013 rule 9's table, in the spelling this platform uses. The package name keeps dnf from
+# treating one as an upgrade of the other; the directory under /opt keeps the two trees apart on disk;
+# the /usr/bin name and the desktop entry keep them apart in front of a person, who would otherwise
+# have two identical launchers and no way to tell which was which.
+#
+# The fifth separation — the profile directory holding the vault cache, the outbox and the device key
+# — is not here and must not be, because it belongs to the build rather than to the package: the
+# nightly is published with DodoChannel=nightly, and ClientPaths reads that to suffix the directory.
+# Doing it here as well would be a second answer to a question that already has one.
+if [ "$channel" = nightly ]; then
+    name=dodossh-nightly
+    dir=DodoSSH.Nightly
+    bin=dodossh-nightly
+    title="DodoSSH Nightly"
+else
+    name=dodossh
+    dir=DodoSSH
+    bin=dodossh
+    title="DodoSSH"
+fi
+
+# ◆ SEMVER IS NOT AN RPM VERSION, AND THE TRANSLATION IS THE ONE PLACE THIS CAN GO QUIETLY WRONG.
+#
+# rpm forbids `-` in a version, which is exactly the character SemVer uses to introduce a prerelease.
+# MinVer's answer on main is 0.0.1-alpha.0.143, so the naive move — strip the suffix — would give
+# every nightly the version 0.0.1 and make each one look like a reinstall of the last.
+#
+# `~` is rpm's own answer and has been since 4.10: it sorts *before* the empty string, so
+# 0.0.1~alpha.0.143 is older than 0.0.1 the way alpha.143 is older than the release. Heights keep
+# rising within a floored version and the first real tag moves past all of them, which is the same
+# ordering property the Velopack channels have and is worth having on both.
+#
+# Build metadata after `+` is dropped rather than translated. It is the one part of a SemVer string
+# that is defined as not participating in ordering, so keeping it would put a character rpm has no
+# rule for into the field ordering is done on.
+rpm_version="${version%%+*}"
+rpm_version="${rpm_version/-/\~}"
+
+case "$rpm_version" in
+    *-*)
+        echo "The version $version translates to $rpm_version, which still contains a hyphen." >&2
+        echo "rpm cannot order a version with one in it; this needs a rule rather than a retry." >&2
+        exit 1
+        ;;
+esac
+
+# Always 1. The release field distinguishes several packagings of one upstream version, and there is
+# only ever one packaging here — the version already carries the build height, because upstream and
+# packager are the same repository.
+rpm_release=1
+
+echo "==> $name $rpm_version-$rpm_release.x86_64, from $payload"
+
+# ◆ rpmbuild ON A MUSL HOST, WHICH IS FINE, AND WHY IT IS WORTH SAYING SO.
+#
+# The runner is Alpine. Nothing about that shows up in the package: rpmbuild composes an archive and
+# some metadata, and the one part of it that reads the payload — elfdeps, which the spec leaves on for
+# requires — parses ELF headers with libelf rather than loading anything, so it reads x86_64 glibc
+# binaries on a musl host correctly. Building in a Fedora container was the alternative and would
+# have meant `docker cp`-ing a 130 MB publish tree in and the package back out, because this runner is
+# itself a container and a bind mount resolves on the daemon's host rather than here — see the note on
+# the android job for the hour that cost.
+if ! command -v rpmbuild >/dev/null 2>&1; then
+    SUDO=""
+    [ "$(id -u)" -eq 0 ] || SUDO="sudo"
+
+    echo "==> installing rpm"
+    if command -v apk >/dev/null 2>&1; then
+        $SUDO apk add --no-cache rpm
+    elif command -v dnf >/dev/null 2>&1; then
+        $SUDO dnf install -y rpm-build
+    elif command -v apt-get >/dev/null 2>&1; then
+        $SUDO apt-get update -qq
+        $SUDO apt-get install -y --no-install-recommends rpm
+    else
+        echo "No apk, dnf or apt-get here, so rpmbuild cannot be installed from inside the job." >&2
+        echo "Add rpm to the runner's image; the Linux package cannot be built without it." >&2
+        exit 1
+    fi
+fi
+rpmbuild --version
+
+# ◆ THE LIST OF PRIVATE SONAMES, WORKED OUT FROM THE TREE RATHER THAN WRITTEN DOWN.
+#
+# build/linux/dodossh.spec turns rpm's automatic provides off for everything under /opt, because the
+# libraries there are this application's private copies and have no business satisfying anybody
+# else's dependency. The requires side has to be told the same thing about the same set, or a bundled
+# library that links another bundled library asks for a soname nothing provides and the package
+# becomes uninstallable on every host — which .NET's own libmscordbi.so, linking libmscordaccore.so,
+# does on every publish.
+#
+# Derived here because the set belongs to the payload. A list in the spec would be Microsoft's and
+# SkiaSharp's internal file names, maintained by hand, going stale on the first runtime bump — and
+# going stale in the direction that produces a package nobody can install.
+#
+# Only the top level is scanned, which is where a .NET publish puts its native libraries. The dots
+# are escaped because this becomes a regular expression; nothing else in a soname is a metacharacter.
+#
+# A shell glob rather than `find -printf`, which is GNU find's and not busybox's — the runner is
+# Alpine, where that flag is a usage message and an empty list, which would silently disable the whole
+# exclusion and put the uninstallable package back.
+bundled="$(
+    for library in "$payload"/lib*.so*; do
+        [ -f "$library" ] && basename "$library"
+    done |
+        sed 's/\./\\./g' |
+        sort -u |
+        paste -sd '|' -
+)"
+
+if [ -z "$bundled" ]; then
+    echo "There are no native libraries at the top of $payload." >&2
+    echo "A self-contained .NET publish always has some, so this is a publish that went wrong" >&2
+    echo "rather than a package with nothing to exclude." >&2
+    exit 1
+fi
+
+work="$(mktemp -d)"
+trap 'rm -rf "$work"' EXIT
+
+mkdir -p "$out"
+
+# --target rather than trusting the host's arch, because the host's arch here is whatever the runner
+# happens to be and the payload's is decided by the RID the publish asked for. They agree today and
+# an aarch64 runner would silently make them disagree.
+#
+# `dist` is emptied deliberately. It is the %{?dist} tag that puts .fc42 in a filename, and it names
+# the distribution the package was *built* on — which for a self-contained tree built on Alpine would
+# be both meaningless and, if rpm guessed something plausible, actively misleading.
+rpmbuild -bb "$repo_root/build/linux/dodossh.spec" \
+    --target x86_64 \
+    --define "_topdir $work" \
+    --define "_rpmdir $out" \
+    --define "dist %{nil}" \
+    --define "dodo_name $name" \
+    --define "dodo_version $rpm_version" \
+    --define "dodo_release $rpm_release" \
+    --define "dodo_dir $dir" \
+    --define "dodo_bin $bin" \
+    --define "dodo_title $title" \
+    --define "dodo_payload $payload" \
+    --define "dodo_bundled $bundled" \
+    --define "dodo_icons $repo_root/src/DodoSSH.Client.App/Assets" \
+    --define "dodo_licence $repo_root/LICENSE"
+
+# rpmbuild writes into <_rpmdir>/<arch>/, and every caller wants the file rather than the tree.
+rpm_file="$out/x86_64/$name-$rpm_version-$rpm_release.x86_64.rpm"
+if [ ! -s "$rpm_file" ]; then
+    echo "rpmbuild reported success and there is no package at $rpm_file." >&2
+    find "$out" >&2 || true
+    exit 1
+fi
+mv "$rpm_file" "$out/"
+rmdir "$out/x86_64" 2>/dev/null || true
+rpm_file="$out/$(basename "$rpm_file")"
+
+echo "==> $(basename "$rpm_file"), $(wc -c < "$rpm_file") bytes"
+
+# ◆ AND NOW THE PART THAT IS NOT PACKAGING: ASKING THE PACKAGE WHAT IT SAYS ABOUT ITSELF.
+#
+# Everything above can succeed and still produce something nobody can install, and none of the ways
+# that happens are visible in an exit code. Each check below is one of them.
+
+requires="$(rpm -qp --requires "$rpm_file")"
+provides="$(rpm -qp --provides "$rpm_file")"
+files="$(rpm -qp --list "$rpm_file")"
+
+# 1. The bundled-soname trap the spec's provides exclusion sets. If some library under /opt ever
+#    gains a DT_NEEDED on another library under /opt, elfdeps will put that soname in the requires
+#    while the exclusion keeps it out of the provides, and the result is a package no host on earth
+#    can satisfy. Nothing about it looks wrong until an install fails, so it is checked here against
+#    the actual contents rather than assumed.
+carried="$(printf '%s\n' "$files" | sed -n 's|^/opt/.*/\(lib[^/]*\.so[^/]*\)$|\1|p' | sort -u)"
+unsatisfiable=""
+for soname in $carried; do
+    if printf '%s\n' "$requires" | grep -qF "$soname("; then
+        unsatisfiable="$unsatisfiable $soname"
+    fi
+done
+if [ -n "$unsatisfiable" ]; then
+    echo "This package requires sonames it also carries and does not provide:$unsatisfiable" >&2
+    echo "That is unsatisfiable on every host, and it means the requires exclusion computed above" >&2
+    echo "no longer matches what rpm generated — a bundled library outside the top level, or an rpm" >&2
+    echo "that has stopped honouring __requires_exclude. See build/linux/dodossh.spec." >&2
+    exit 1
+fi
+
+# 2. The provides exclusion still doing its job. A package advertising libcoreclr.so to the whole
+#    system is the thing that exclusion exists to prevent, and a future rpm that stopped honouring
+#    the macro would break it silently and in the direction nobody looks.
+if printf '%s\n' "$provides" | grep -qE '^lib.*\.so'; then
+    echo "This package advertises bundled libraries to the system:" >&2
+    printf '%s\n' "$provides" | grep -E '^lib.*\.so' >&2
+    echo "__provides_exclude_from in build/linux/dodossh.spec is meant to stop that." >&2
+    exit 1
+fi
+
+# 3. elfdeps having actually run. If it silently did nothing — a runner image whose rpm was built
+#    without libelf would do exactly that — the package would carry no glibc requirement at all and
+#    would install cheerfully onto a host too old to run it. libc.so.6 is the one dependency a
+#    self-contained .NET tree cannot fail to have.
+if ! printf '%s\n' "$requires" | grep -q '^libc\.so\.6'; then
+    echo "This package does not require libc, which a self-contained .NET tree cannot be true of." >&2
+    echo "The automatic ELF scan produced nothing; rpm here is probably built without elfdeps." >&2
+    printf '%s\n' "$requires" >&2
+    exit 1
+fi
+
+# 4. The four files a person interacts with, named individually. The tree under /opt is thousands of
+#    entries and its absence would be caught by size alone; these are the small ones whose absence
+#    would leave a package that installs, occupies 130 MB and puts nothing on the menu.
+for expected in \
+    "/opt/$dir/DodoSSH" \
+    "/usr/bin/$bin" \
+    "/usr/share/applications/$bin.desktop" \
+    "/usr/share/icons/hicolor/256x256/apps/$bin.png"
+do
+    if ! printf '%s\n' "$files" | grep -qxF "$expected"; then
+        echo "The package was built and $expected is not in it." >&2
+        printf '%s\n' "$files" | head -40 >&2
+        exit 1
+    fi
+done
+
+# 5. Nothing world-writable, which on this package is a security property rather than a lint rule.
+#    The spec sets every mode explicitly and says why; this is the check that it worked, because the
+#    failure it guards against arrives by inheritance from a publish directory rather than by anybody
+#    changing this. A world-writable /opt/DodoSSH lets any local account replace the SSH client every
+#    other account on the machine runs.
+#
+#    Symlinks are excluded because they are always 777 on Linux and the mode means nothing; what the
+#    link points at is what has permissions.
+writable="$(
+    rpm -qp --queryformat '[%{FILEMODES:perms} %{FILENAMES}\n]' "$rpm_file" |
+        grep -v '^l' |
+        awk '$1 ~ /^.{8}w/ { print }'
+)"
+if [ -n "$writable" ]; then
+    echo "This package contains world-writable files:" >&2
+    printf '%s\n' "$writable" >&2
+    echo "Any local account could replace them. See the mode block in build/linux/dodossh.spec." >&2
+    exit 1
+fi
+
+echo "==> requires:"
+printf '%s\n' "$requires" | sed 's/^/    /'
+
+echo "==> $(basename "$rpm_file") is a $name $rpm_version package and says so."
+
+# The one line the calling job reads. Written to stdout as well as to GITHUB_OUTPUT when there is one,
+# so the desk use above still tells you where the file went.
+if [ -n "${GITHUB_OUTPUT:-}" ]; then
+    {
+        echo "rpm=$rpm_file"
+        echo "rpmName=$(basename "$rpm_file")"
+    } >> "$GITHUB_OUTPUT"
+fi
+echo "$rpm_file"

src/DodoSSH.Client.App/Assets/dodossh-icon.ps1

@@ -225,3 +225,37 @@ $icnsTarget = Join-Path $PSScriptRoot 'dodossh.icns'
 $icns.Dispose()
 
 Write-Output "Wrote $icnsTarget ($($icnsTypes.Count) entries, $((Get-Item $icnsTarget).Length) bytes)"
+
+# ---- dodossh-<size>.png, for the Linux desktop entry ---------------------------------------------
+#
+# The third platform, and the only one that wants the raster loose rather than in a container. A
+# freedesktop icon theme is a directory tree — hicolor/48x48/apps/dodossh.png and friends — and the
+# RPM built by scripts/ci-linux-rpm.sh installs one file per size into it.
+#
+# Written here for the reason this whole file exists: one geometry, regenerated in one command. The
+# alternative was to have the packaging script pull the 256px frame out of dodossh.ico at build time,
+# which works — the .ico's entries really are PNGs — and puts a second place that has to know how an
+# ICO directory is laid out. It also silently ties the Linux icon to whatever sizes Windows happens
+# to want.
+#
+# ◆ THE TILE BLEEDS TO THE EDGE HERE, AS IT DOES ON WINDOWS.
+#
+# tileFraction stays 1.0. The 0.8047 inset above is Apple's icon grid and nothing else — GNOME, KDE
+# and every panel that reads hicolor draw the icon at the size they asked for, with no shadow and no
+# magnification to leave air for. An inset icon would simply be the small one in the launcher.
+#
+# ◆ AND THE SIZES ARE NOT A ROUND NUMBER OF THEM.
+#
+# 48 is the size a GNOME dash and most panels ask for, 128 and 256 are what a large-icon file manager
+# and GNOME Software use, and 64 is between them because the 48 upscaled to it is visibly soft. There
+# is deliberately nothing below 48: the hairline floor in New-MarkPng keeps a 16px mark legible, but
+# no Linux desktop asks this theme for one — window titlebars there draw no icon at all.
+$linuxSizes = @(48, 64, 128, 256)
+
+foreach ($size in $linuxSizes)
+{
+    [byte[]]$png = New-MarkPng $size
+    $pngTarget = Join-Path $PSScriptRoot "dodossh-$size.png"
+    [System.IO.File]::WriteAllBytes($pngTarget, $png)
+    Write-Output "Wrote $pngTarget ($((Get-Item $pngTarget).Length) bytes)"
+}