Current File : //snap/core20/current/usr/lib/core/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 core20+ 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"
Mini Shell