Remove fstab from squashfs images

The default fstab is not valid, since squashfs does not support labels.

LP: #1877078

live-build/auto/config

@@ -35,6 +35,7 @@ mkdir -p config
 cp -af /usr/share/livecd-rootfs/live-build/functions config/functions
 cp -af /usr/share/livecd-rootfs/live-build/lb_*_layered config/
 cp -af /usr/share/livecd-rootfs/live-build/snap-seed-parse.py config/snap-seed-parse
+cp -af /usr/share/livecd-rootfs/live-build/squashfs-exclude-files config/
 
 mkdir -p config/package-lists
 

live-build/functions

@@ -277,6 +277,17 @@ create_vmdk() {
     rm -rf ${scratch_d}
 }
 
+create_squashfs() {
+    local config_dir rootfs_dir squashfs_file
+    rootfs_dir="$1"
+    squashfs_file="$2"
+    config_dir="$PWD/config"
+    (cd $rootfs_dir &&
+        mksquashfs . $squashfs_file -no-progress -xattrs -comp xz \
+            -ef "$config_dir/squashfs-exclude-files")
+
+}
+
 create_derivative() {
     # arg1 is the disk type
     # arg2 is the new name

live-build/squashfs-exclude-files

@@ -0,0 +1 @@
+etc/fstab

live-build/ubuntu-cpc/hooks.d/base/root-squashfs.binary

@@ -8,14 +8,15 @@ if [ -n "$SUBARCH" ]; then
 	exit 0
 fi
 
+. config/functions
+
 # This is the directory created by create-root-dir.binary
 rootfs_dir=rootfs.dir
 
 squashfs_f="$PWD/livecd.ubuntu-cpc.squashfs"
 
 cp $rootfs_dir.manifest $squashfs_f.manifest
-cp $rootfs_dir.filelist $squashfs_f.filelist
+# fstab is omitted from the squashfs
+grep -v '^/etc/fstab$' $rootfs_dir.filelist >$squashfs_f.filelist
 
-(cd $rootfs_dir &&
-      mksquashfs . $squashfs_f \
-        -no-progress -xattrs -comp xz )
+create_squashfs $rootfs_dir $squashfs_f

live-build/ubuntu-server/hooks/030-root-squashfs.binary

@@ -30,6 +30,4 @@ squashfs_f_manifest="${squashfs_f}.manifest"
 
 create_manifest "binary/boot/squashfs.dir" "${squashfs_f_manifest}"
 
-(cd "binary/boot/squashfs.dir/" &&
-      mksquashfs . ${squashfs_f} \
-        -no-progress -xattrs -comp xz )
+create_squashfs "binary/boot/squashfs.dir/" ${squashfs_f}

live-build/ubuntu-server/hooks/032-installer-squashfs.binary

@@ -86,6 +86,4 @@ teardown_mountpoint "$INSTALLER_ROOT"
 
 squashfs_f="${PWD}/livecd.${PROJECT}.installer.squashfs"
 
-(cd "$OVERLAY_ROOT/" &&
-      mksquashfs . ${squashfs_f} \
-        -no-progress -xattrs -comp xz )
+create_squashfs "$OVERLAY_ROOT/" ${squashfs_f}