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authorAlex Xu (Hello71) <alex_y_xu@yahoo.ca>2021-06-23 09:04:32 -0400
committerAlex Xu (Hello71) <alex_y_xu@yahoo.ca>2021-06-23 09:04:32 -0400
commited9913745c36e9244cea831bbb7efb3e1d4544bc (patch)
tree635855042203cda104ce31a630abcd57162d2fde
parent01395e3a8d86bfc67f4b0beb0d510d65df0eb340 (diff)
downloadtmpoverlay-ed9913745c36e9244cea831bbb7efb3e1d4544bc.tar.xz
tmpoverlay-ed9913745c36e9244cea831bbb7efb3e1d4544bc.zip
revamp cleanup, perm copying (broken before)
-rw-r--r--README.rst2
-rwxr-xr-xtmpoverlay147
2 files changed, 70 insertions, 79 deletions
diff --git a/README.rst b/README.rst
index 231041c..ceeaf84 100644
--- a/README.rst
+++ b/README.rst
@@ -14,7 +14,7 @@ Benefits over manually calling ``mkdir /tmp/x; mount ...``
- separate tmpfs allows size limit (``tmpoverlay -t size=SIZE``)
- upperdir and workdir automatically managed
- tmpfs cleanup after mount so that umount frees RAM
-- synchronizes owner, permissions, and xattrs (including lowerdir ACL)
+- synchronizes owner, permissions, and xattrs (including ACLs)
- autodetects optimization flags (redirect_dir, metacopy, index, volatile)
Overmounting
diff --git a/tmpoverlay b/tmpoverlay
index d5e84f2..b2fe6d9 100755
--- a/tmpoverlay
+++ b/tmpoverlay
@@ -1,6 +1,7 @@
#!/bin/sh
usage() {
+ [ "$1" = 0 ] || exec >&2
cat << EOF
usage: tmpoverlay [OPTIONS] [SOURCE...] DEST
@@ -22,21 +23,26 @@ examples:
tmpoverlay /a /b /c /merged # merge /a, /b, /c, and a fresh tmpfs
tmpoverlay / # USE WITH CAUTION, see docs
EOF
+ exit "$1"
}
log() {
- fmt=$1
- shift
- printf 'tmpoverlay: ' >&2
- # shellcheck disable=SC2059
- printf "$fmt" "$@" >&2
+ logn "$@"
printf '\n' >&2
}
+logn() {
+ # not equivalent to printf "tmpoverlay: $@"
+ printf 'tmpoverlay: ' >&2
+ printf "$@" >&2
+}
+
logv() {
- if [ -n "$verbose" ]; then
- log "$@"
- fi
+ [ -z "$verbose" ] || log "$@"
+}
+
+logvn() {
+ [ -z "$verbose" ] || logn "$@"
}
cmdv() {
@@ -44,34 +50,12 @@ cmdv() {
"$@"
}
-unset own_tmpdir
+unset tmpdir
die() {
r=$?
- trap - INT TERM QUIT
- unset sig
- case $1 in
- -[A-Z]*) sig=${1#-};;
- '') ;;
- *) log "$@"
- esac
- logv 'an error occurred, cleaning up'
- if [ -d "$tmpdir" ] && [ -n "$own_tmpdir" ]; then
- if mountpoint -q "$tmpdir"; then
- logv 'unmounting tmpdir'
- # shellcheck disable=SC2086
- umount $no_mtab "$tmpdir"
- fi
- logv 'deleting tmpdir'
- rmdir "$tmpdir"
- fi
- if [ -n "$sig" ]; then
- logv 'reraising SIG%s' "$1"
- kill "-$1" "$$" && read -r _
- fi
- logv 'exiting'
- if [ $r = 0 ]; then
- exit 1
- fi
+ [ "$r" != 0 ] || r=1
+ [ "$#" = 0 ] || log "$@"
+ [ -z "$tmpdir" ] || { exec 9>&-; wait; }
exit $r
}
@@ -98,7 +82,7 @@ my_getopt() {
"$@"
}
-args=$(my_getopt "$@") || { usage >&2; exit 1; }
+args=$(my_getopt "$@") || usage 1
eval set -- "$args"
unset args
@@ -106,7 +90,7 @@ unset no_canon extra_ovl_opts no_mtab mount_name tmpfs_opts verbose
while true; do
case "$1" in
-c|--no-canonicalize) no_canon=-c; shift;;
- -h|--help) usage; exit 0;;
+ -h|--help) usage 0;;
-o|--overlayfs)
[ -n "$2" ] && extra_ovl_opts="$extra_ovl_opts,$2"
shift 2
@@ -123,7 +107,7 @@ while true; do
esac
done
-[ $# != 0 ] || { log 'no paths specified'; usage >&2; exit 1; }
+[ $# != 0 ] || usage 1
unset lowerdir
while [ "$#" != 1 ]; do
@@ -139,21 +123,34 @@ dest=$(canon "$1")
[ -d "$dest" ] || die 'destination "%s" is not a directory' "$dest"
[ "$dest" != / ] || log 'overmounting root, use with caution'
-if [ -z "$lowerdir" ]; then
- lowerdir=$dest
-fi
-
-trap 'die -INT' INT
-trap 'die -TERM' TERM
-trap 'die -QUIT' QUIT
-
-if [ -z "$tmpdir" ]; then
- logv 'creating tmpdir'
- own_tmpdir=1
- tmpdir=$(umask 077; mktemp -dt tmpoverlay.XXXXXXXXXX) || exit 1
- logv 'created tmpdir: %s' "$tmpdir"
-fi
-mount -t tmpfs ${tmpfs_opts:+-o "$tmpfs_opts"} ${verbose:+-v} tmpfs "$tmpdir" || die
+[ -n "$lowerdir" ] || lowerdir=$dest
+
+logv 'creating tmpdir'
+tmpdir=$(umask 077; mktemp -dt tmpoverlay.XXXXXXXXXX) || die
+logv 'created tmpdir: %s' "$tmpdir"
+case "$tmpdir" in
+ "$dest"/*) log "warning: tmpdir cannot be cleaned up after overmounting $dest"
+esac
+mount -t tmpfs ${tmpfs_opts:+-o "$tmpfs_opts"} $verbose tmpfs "$tmpdir" || { rmdir "$tmpdir"; die; }
+mkfifo "$tmpdir/fifo" || { umount "$tmpdir"; rmdir "$tmpdir"; die; }
+# subshell allows cleanup after overmount /tmp without using realpath source
+# subshell also avoids trapping signals which is annoying in shell
+(
+ cd "$tmpdir" || die
+ exec <fifo || die
+ # read returns non-zero when write end is closed
+ read _
+ logv 'unmounting tmpdir'
+ # TODO: this *almost* works except umount insists on canonicalizing .
+ # shellcheck disable=SC2086
+ umount -cil $no_mtab . || die
+ logv 'deleting tmpdir'
+ cd /
+ rmdir "$tmpdir" || die
+) &
+# should be FD_CLOEXEC but can't do in shell
+exec 9>"$tmpdir/fifo"
+# starting from here, exiting will cause cleanup
upperdir="$tmpdir/upper"
workdir="$tmpdir/work"
@@ -168,7 +165,7 @@ umount "$tmpmnt"
if [ -n "$extra_ovl_opts" ]; then
ovl_opts="$ovl_opts,$extra_ovl_opts"
mount -n -t overlay -o "$ovl_opts" overlay "$tmpmnt" || die "invalid extra overlayfs options"
- umount "$tmpmnt"
+ umount "$tmpmnt" || die
fi
chk_ovl_opt() {
if [ -n "$2" ]; then
@@ -189,12 +186,16 @@ try_ovl_opt() {
*",$1[=,]"*) return 0
esac
if chk_ovl_opt "$1"; then
- logv 'skipping %s'
+ logv 'not checking %s'
return
fi
- logv 'trying %s' "$1${2+=$2}"
+ logvn 'trying %s... ' "$1${2+=$2}"
new_ovl_opts="$ovl_opts,$1${2+=$2}"
- mount -n -t overlay -o "$new_ovl_opts" "overlay" "$tmpmnt" 2>/dev/null || return
+ if ! cmdv mount -n -t overlay -o "$new_ovl_opts" "overlay" "$tmpmnt" 2>/dev/null; then
+ [ -z "$verbose" ] || echo rejected >&2
+ return
+ fi
+ [ -z "$verbose" ] || echo ok >&2
umount "$tmpmnt" || die
# clear out workdir/work/incompat/volatile and upperdir index
rm -r "$workdir" "$upperdir" || die
@@ -212,21 +213,15 @@ try_ovl_opt volatile
logv 'copying lowerdir owner/perms to upperdir'
lastlowerdir=${lowerdir##*:}
-# stat -c isn't posix -.-
+# stat -c isn't posix, but ls is
ls=$(ls -dn "$lastlowerdir/.") || die
-tmp=${ls#* * }
-owner=${tmp%% *}
-tmp=${tmp#* }
-group=${tmp%% *}
-chown "$owner:$group" "$upperdir" || die
-mode=${ls%% *}
-[ "${#mode}" = 10 ] || die "bad ls permission format"
-mode=${mode#?}
-umode=${mode%??????}
-ugmode=${mode%???}
-gmode=${ugmode#???}
-omode=${mode#??????}
-chmod "u=$umode,g=$gmode,o=$omode" "$upperdir" || die
+[ -n "$ls" ] || die 'empty ls output'
+owner=$(printf '%s\n' "$ls" | sed -e 's/^[^ ]* [^ ]* \([^ ]*\) \([^ ]*\).*$/\1:\2/;t;d')
+[ -n "$owner" ] || die 'bad ls owner output'
+mode=$(printf '%s\n' "$ls" | sed -e 's/^d\(...\)\(...\)\(...\).*/u=\1,g=\2,o=\3/;s/-//g;t;d')
+[ -n "$mode" ] || die 'bad ls mode output'
+cmdv chown "$owner" "$upperdir" || die
+cmdv chmod "$mode" "$upperdir" || die
# -m - covers ACLs (system.posix_acl_access) and file caps
# (security.capability). theoretically someone might have get/setcap and/or
# get/setfacl but not get/setxattr, but this is unlikely since libcap/acl
@@ -237,16 +232,12 @@ if attrs=$(cd "$lastlowerdir" && getfattr -d -m - . 2>/dev/null); then
printf '%s\n' "$attrs" | (cd "$upperdir"; setfattr --restore=-) || die
fi
else
- log 'getfattr failed, skipping xattrs'
+ log 'getfattr failed, skipping xattrs/ACLs'
fi
logv 'mounting overlay'
-mount_opts="$no_canon $no_mtab $verbose"
# shellcheck disable=SC2086
-cmdv mount $mount_opts -t overlay -o "$ovl_opts" "${mount_name-overlay}" "$dest" || die
-
-logv 'cleaning up'
-umount "$tmpdir" || exit
-rmdir "$tmpdir" || exit
-
+cmdv mount $no_canon $no_mtab $verbose -t overlay -o "$ovl_opts" "${mount_name-overlay}" "$dest" || die
+exec 9>&-
+wait || die
logv 'done'