name : handle-writable-paths #!/bin/sh # # Extracted code from: # https://github.com/snapcore/core-build/blob/master/initramfs/scripts/ubuntu-core-rootfs # to keep in the core22+ snap in sync with the writable-path file. # # Having it here means we don't need to rebuld all kernels if this file # changes. set -e panic() { echo "PANIC: $*" exit 1 } # XXX: we really want the "synced" feature to go away sync_dirs() { base="$1" source="$2" target="$3" OLD_PWD="$PWD" cd "$base" for file in "$source"/* do # Skip empty directories [ ! -e "$base/$file" -a ! -L "$base/$file" ] && continue # If the target already exists as a file or link, there's nothing we can do [ -e "$target/$file" -o -L "$target/$file" ] && [ ! -d "$target/$file" ] && continue # If the target doesn't exist, just copy it over if [ ! -e "$target/$file" -a ! -L "$target/$file" ]; then cp -Ra "$base/$file" "$target/$file" continue fi # That leaves us with directories and a recursive call [ -d "$file" ] && sync_dirs "$base" "$file" "$target" done cd "$OLD_PWD" } # Process the list of bind-mounts (but don't mount them - systemd will handle that) # File format is documented in writable-paths(5). handle_writable_paths() { writable_paths="$1" fstab="$2" [ -n "$writable_paths" ] || panic "need writeable paths" [ -e "$writable_paths" ] || panic "writeable paths does not exist" [ -n "$fstab" ] || panic "need fstab" cat "$writable_paths" | while read line; do # tokenise set -- $line # skip invalid/commented entries ([ -z "$1" ] || \ [ -z "$2" ] || \ [ -z "$3" ] || \ [ -z "$4" ] || \ [ -z "$5" ]) && continue # ignore anything that isn't an absolute path (including comments) case "$1" in /*) ;; *) continue ;; esac # skip invalid mount points dstpath="${rootmnt}$1" [ ! -e "$dstpath" ] && continue if [ "$3" = "temporary" ]; then # Temporary entries are simple, just mount a tmpfs echo "tmpfs $1 tmpfs $5 0 0" >> "$fstab" elif [ "$3" = "persistent" ] || \ [ "$3" = "synced" ]; then # Figure out the source path if [ "$2" = "auto" ]; then srcpath="${rootmnt}/writable/system-data${1}" path="/writable/system-data${1}" else srcpath="${rootmnt}/writable/$2" path="/writable/$2" fi if [ ! -e "$srcpath" ]; then # Process new persistent or synced paths dstown=$(stat -c "%u:%g" "$dstpath") dstmode=$(stat -c "%a" "$dstpath") mkdir -p ${srcpath%/*} if [ ! -d "$dstpath" ]; then # Deal with redirected files if [ "$4" = "transition" ]; then cp -a "$dstpath" "$srcpath" else touch "$srcpath" chown "$dstown" "$srcpath" chmod "$dstmode" "$srcpath" fi else # Deal with redirected directories if [ "$4" = "transition" ] || [ "$3" = "synced" ]; then cp -aR "$dstpath" "$srcpath" else mkdir "$srcpath" chown "$dstown" "$srcpath" chmod "$dstmode" "$srcpath" fi fi elif [ "$3" = "synced" ]; then # Process existing synced paths sync_dirs "$dstpath" . "$srcpath" fi # mount all /etc dirs right now, not later when fstab is # processed, as it will cause races. case $1 in /etc*) [ -e "${rootmnt}/writable/system-data/$1" ] || mkdir -p "${rootmnt}/writable/system-data/$1" mount -o bind "${rootmnt}/writable/system-data/$1" "${rootmnt}/$1" ;; *) # Write the fstab entry if [ "$5" = "none" ]; then echo "$path $1 none bind 0 0" >> "$fstab" else echo "$path $1 none bind,$5 0 0" >> "$fstab" fi ;; esac else continue fi done # now apply the defaults on top handle_writable_defaults } # handle_writable_default will apply system defaults *once* after # the handle_writable_path got populated handle_writable_defaults() { srcpath="${rootmnt}/writable/system-data/_writable_defaults" if [ ! -d "$srcpath" ] || [ -e "${srcpath}/.done" ]; then return fi dstpath="${rootmnt}/writable/system-data" for fileordir in "$srcpath"/* ; do # skip empty $srcpath/ [ ! -e "$fileordir" ] && [ ! -L "$fileordir" ] && continue # copy cp -a "$fileordir" "$dstpath" done touch "$srcpath/.done" } main() { writable_paths="${1:-${rootmnt}/etc/system-image/writable-paths}" fstab="${2:-${rootmnt}/etc/fstab}" # Add writable overlays if [ -e "$writable_paths" ]; then touch "${rootmnt}/run/image.fstab" mount -o bind "${rootmnt}/run/image.fstab" "$fstab" || panic "Cannot bind mount fstab" echo "# Auto-generated by $0" >> "$fstab" echo "# DO NOT EDIT THIS FILE BY HAND - YOUR CHANGES WILL BE OVERWRITTEN" >> "$fstab" echo "# (See writable-paths(5) for details)" >> "$fstab" echo "/dev/root / rootfs defaults,ro 0 0" >> "$fstab" handle_writable_paths "$writable_paths" "$fstab" echo "/run/mnt/ubuntu-seed /var/lib/snapd/seed none bind,ro 0 0" >> "$fstab" fi # IMPORTANT: ensure we synced everything back to disk sync } # for unit test if [ "$TEST_IMPORT" = "1" ]; then return fi rootmnt="$1" if [ -z "$rootmnt" ]; then echo "need rootmnt as the first argument" exit 1 fi # "$2" is the (optional) writable-paths file # "$3" is the (optional) /etc/fstab file main "$2" "$3"