diff options
| -rw-r--r-- | README.rst | 2 | ||||
| -rwxr-xr-x | tmpoverlay | 147 |
2 files changed, 70 insertions, 79 deletions
@@ -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 @@ -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' |