First commit to enable an environmental variable that points to current rootfs directory can be improved to avoid risk of selecting the wrong partition/path when user have added additional partitions to be used with for example containers.
Suggestion to use the same method as "image_name" in /src/init/vyos-router which also is less likely to select wrong path because the source will now be cmdline.
Looks like its working as expected in VyOS 1.4-rolling-202308140557:
vyos@vyos:~$ export | grep -i rootfs
declare -rx vyos_rootfs_dir="/usr/lib/live/mount/rootfs/1.4-rolling-202308140557.squashfs"
vyos@vyos:~$ cd ${vyos_rootfs_dir}
vyos@vyos:/usr/lib/live/mount/rootfs/1.4-rolling-202308140557.squashfs$ ls -la
total 4
drwxr-xr-x 17 root root 308 Aug 14 07:57 .
drwxr-xr-x 3 root root 4096 Aug 14 22:20 ..
lrwxrwxrwx 1 root root 7 Aug 14 07:57 bin -> usr/bin
drwxr-xr-x 3 root root 197 Aug 14 07:57 boot
drwxr-xr-x 4 root root 191 Aug 14 07:57 dev
drwxr-xr-x 134 root root 4352 Aug 14 07:57 etc
drwxr-xr-x 18 root root 261 Aug 14 07:57 home
lrwxrwxrwx 1 root root 7 Aug 14 07:57 lib -> usr/lib
lrwxrwxrwx 1 root root 9 Aug 14 07:57 lib32 -> usr/lib32
lrwxrwxrwx 1 root root 9 Aug 14 07:57 lib64 -> usr/lib64
lrwxrwxrwx 1 root root 10 Aug 14 07:57 libx32 -> usr/libx32
drwxr-xr-x 2 root root 3 Aug 14 07:57 media
drwxr-xr-x 2 root root 3 Aug 14 07:57 mnt
drwxr-xr-x 3 root root 29 Aug 14 07:57 opt
drwxr-xr-x 2 root root 3 Jul 14 18:00 proc
drwx------ 4 root root 72 Aug 14 07:57 root
drwxr-xr-x 28 root root 436 Aug 14 07:57 run
lrwxrwxrwx 1 root root 8 Aug 14 07:57 sbin -> usr/sbin
drwxr-xr-x 4 root root 42 Aug 14 07:57 srv
drwxr-xr-x 2 root root 3 Jul 14 18:00 sys
drwxrwxrwt 2 root root 3 Aug 14 07:57 tmp
drwxr-xr-x 14 root root 217 Aug 14 07:57 usr
drwxr-xr-x 13 root root 183 Aug 14 07:57 var
vyos@vyos:/usr/lib/live/mount/rootfs/1.4-rolling-202308140557.squashfs$ cat /etc/default/vyatta | grep -i rootfs
if test -z "$vyos_rootfs_dir" ; then
declare -x -r vyos_rootfs_dir="/usr/lib/live/mount/rootfs/${IMAGE_NAME}.squashfs"
vyos@vyos:/usr/lib/live/mount/rootfs/1.4-rolling-202308140557.squashfs$