build(gui-client): add post-install and pre-remove scripts to the deb package (#5011)

Closes #4987

```[tasklist]
### Before merging
- [x] Get an x64 test VM on the Windows laptop and test a CI-built deb
```

rust/gui-client/build.sh

@@ -2,6 +2,9 @@
 
 set -euo pipefail
 
+# Dir where all the bundles are built
+BUNDLES_DIR=../target/release/bundle/deb
+
 # Copy frontend dependencies
 cp node_modules/flowbite/dist/flowbite.min.js src/
 
@@ -11,5 +14,27 @@ pnpm tsc
 # Compile CSS
 pnpm tailwindcss -i src/input.css -o src/output.css
 
+# Get rid of any existing debs, since we need to discover the path later
+rm -rf "$BUNDLES_DIR"
+
 # Compile Rust and bundle
 pnpm tauri build
+
+# Delete the deb that Tauri built. We're going to modify and rebuild it.
+rm "$BUNDLES_DIR"/*.deb
+
+# There should be only one directory in `bundle/deb`, we need to modify
+# files inside that dir
+INTERMEDIATE_DIR=$(ls -d "$BUNDLES_DIR"/*/)
+
+# Add the scripts
+cp src-tauri/deb_files/postinst src-tauri/deb_files/prerm "$INTERMEDIATE_DIR/control/"
+
+pushd "$INTERMEDIATE_DIR"
+# Rebuild the control tarball
+tar -C "control" -czf "control.tar.gz" control md5sums postinst prerm
+
+# Rebuild the deb package, and give it a predictable name that
+# `tauri-rename-ubuntu.sh` can fix
+ar rcs "../firezone-client-gui.deb" debian-binary control.tar.gz data.tar.gz
+popd

rust/gui-client/docs/intended_behavior.md

@@ -83,9 +83,7 @@ x86_64 only, see issue #2992. Best performed on a clean VM.
 ## Un-install checklist (Linux)
 
 1. Close the Firezone GUI
-1. Run `sudo systemctl stop firezone-client-ipc.service`
 1. Run `sudo apt-get remove firezone-client-gui`
-1. Run `sudo systemctl daemon-reload`
 
 ## Un-install checklist (Windows)
 

rust/gui-client/src-tauri/deb_files/postinst

@@ -0,0 +1,15 @@
+#!/usr/bin/env bash
+# Usage: dpkg will call this after installing our files
+# This must be idempotent
+
+set -euo pipefail
+
+SERVICE_NAME="firezone-client-ipc"
+
+# Creates the system group `firezone-client`
+sudo systemd-sysusers
+
+echo "Starting and enabling Firezone IPC service..."
+sudo systemctl daemon-reload
+sudo systemctl enable "$SERVICE_NAME"
+sudo systemctl restart "$SERVICE_NAME"

rust/gui-client/src-tauri/deb_files/prerm

@@ -0,0 +1,9 @@
+#!/usr/bin/env bash
+# Usage: dpkg will call this after installing our files
+
+set -euo pipefail
+
+SERVICE_NAME="firezone-client-ipc"
+
+sudo systemctl disable "$SERVICE_NAME"
+sudo systemctl stop "$SERVICE_NAME"

scripts/build/tauri-rename-ubuntu.sh

@@ -17,7 +17,7 @@ ls ../target/release ../target/release/bundle/deb
 # Using a glob for the source, there will only be one exe and one deb anyway
 cp ../target/release/firezone-client-gui "$BINARY_DEST_PATH"
 cp ../target/release/firezone-gui-client.dwp "$BINARY_DEST_PATH.dwp"
-cp ../target/release/bundle/deb/*_amd64.deb "$BINARY_DEST_PATH.deb"
+cp ../target/release/bundle/deb/firezone-client-gui.deb "$BINARY_DEST_PATH.deb"
 # TODO: Debug symbols for Linux
 
 function make_hash() {

scripts/firezone-client-gui-install.sh

@@ -9,19 +9,12 @@ set -euox pipefail
 # `apt-get` needs either a leading `./` or `/` to recognize a local file path
 DEB_PATH=$(realpath "$1")
 GROUP_NAME="firezone-client"
-SERVICE_NAME="firezone-client-ipc"
 
 echo "Installing Firezone..."
 sudo apt-get install --yes "$DEB_PATH"
 
 echo "Adding your user to the $GROUP_NAME group..."
-# Creates the system group `firezone-client`
-sudo systemd-sysusers
-sudo adduser "$USER" "$GROUP_NAME"
-
-echo "Starting and enabling Firezone IPC service..."
-sudo systemctl enable "$SERVICE_NAME"
-sudo systemctl restart "$SERVICE_NAME"
+sudo usermod -a -G "$GROUP_NAME" "$USER"
 
 # Check if the user is already in the group
 if ! groups | grep "$GROUP_NAME" &>/dev/null; then