lxd: Build lxd server binary into /sbin

    The PATH inside the snap is configured to prefer /sbin over /bin so the lxd binary will still
    be called by default.

    The lxd-stophook-wrapper script which will be placed into `/bin/lxd`.

    Because containers are configured to call `/snap/lxd/current/bin/lxd callhook` which in turn will be
    routed to `/snap/lxd/current/bin/lxd-user` by the lxd-stophook-wrapper script, which will then connect
    to LXD's unix socket to indicate to the server that the container is stopping.

    Because lxd-user is compiled as a static binary this will work across snap core base changes.

Signed-off-by: Thomas Parrott <[email protected]>

snapcraft.yaml

@@ -1401,7 +1401,12 @@ parts:
 
       # Build the binaries
       go build -trimpath -o "${CRAFT_PART_INSTALL}/bin/lxc" github.com/canonical/lxd/lxc
-      go build -trimpath -o "${CRAFT_PART_INSTALL}/bin/lxd" -tags=libsqlite3 github.com/canonical/lxd/lxd
+
+      # Build LXD server binary into ${CRAFT_PART_INSTALL}/sbin/lxd so that it does not conflict with the
+      # lxd-stophook wrapper script which is stored in ${CRAFT_PART_INSTALL}/bin/lxd.
+      # This way when a container stops it will call "/snap/lxd/current/bin/lxd callhook" which is handled by the
+      # lxd-stophook script, which in turn will execute "/snap/lxd/current/bin/lxd-user callhook" to notify LXD.
+      go build -trimpath -o "${CRAFT_PART_INSTALL}/sbin/lxd" -tags=libsqlite3 github.com/canonical/lxd/lxd
 
       # Build static binaries
       CGO_ENABLED=0 go build -trimpath -o "${CRAFT_PART_INSTALL}/bin/lxd-agent" -tags=agent,netgo github.com/canonical/lxd/lxd-agent
@@ -1440,7 +1445,7 @@ parts:
       usr/share/misc/: share/misc/
       var/lib/usbutils/usb.ids: share/misc/
       usr/sbin/: bin/
-      sbin/: bin/
+      sbin/sgdisk: bin/
     prime:
       - bin/dnsmasq
       - bin/getfattr
@@ -1461,9 +1466,9 @@ parts:
       - share/misc/usb.ids
 
       - bin/lxc
-      - bin/lxd
       - bin/lxd-agent
       - bin/lxd-user
+      - sbin/lxd
 
   lxd-ui:
     source: https://github.com/canonical/lxd-ui
@@ -1546,10 +1551,12 @@ parts:
       rm -rf "${CRAFT_PRIME}/usr/share/"
 
       # Strip binaries (excluding shell scripts and LXCFS)
+      # The "${CRAFT_PRIME}/bin/lxd" file is ignored as that is the lxd-stophook wrapper script.
       find "${CRAFT_PRIME}"/bin -type f \
         -not -path "${CRAFT_PRIME}/bin/ceph" \
         -not -path "${CRAFT_PRIME}/bin/editor" \
         -not -path "${CRAFT_PRIME}/bin/lxc-checkconfig" \
+        -not -path "${CRAFT_PRIME}/bin/lxd" \
         -not -path "${CRAFT_PRIME}/bin/nvidia-container-cli" \
         -not -path "${CRAFT_PRIME}/bin/remote-viewer" \
         -not -path "${CRAFT_PRIME}/bin/snap-query" \
@@ -1561,6 +1568,9 @@ parts:
         -not -path "${CRAFT_PRIME}/bin/gpu-2404-custom-wrapper" \
         -exec strip -s {} +
 
+      # This is the actual LXD binary.
+      strip --strip-all "${CRAFT_PRIME}/sbin/lxd"
+
       # Strip binaries not under bin/ due to being dynamically
       # added to the path with `snap set lxd`, like `criu.enable=true`
       for binary in "${CRAFT_PRIME}/criu/criu"; do