diff options
Diffstat (limited to 'tmpoverlay')
| -rwxr-xr-x | tmpoverlay | 244 |
1 files changed, 0 insertions, 244 deletions
diff --git a/tmpoverlay b/tmpoverlay deleted file mode 100755 index e817e87..0000000 --- a/tmpoverlay +++ /dev/null @@ -1,244 +0,0 @@ -#!/bin/sh - -usage() { - [ "$1" = 0 ] || exec >&2 - cat << EOF -usage: tmpoverlay [OPTIONS] [SOURCE...] DEST - -Create a tmpfs-backed overlayfs at DEST starting with SOURCEs. If no SOURCE is -specified, use DEST as the source. To free the memory, simply umount DEST. - -options: - -c, --no-canonicalize don't canonicalize paths - -h, --help print this help - -o, --overlayfs OPTS add overlayfs mount options, e.g. redirect_dir/metacopy - -n, --no-mtab don't write to /etc/mtab - -N, --mount-name NAME source name for mount (default "overlay") - -t, --tmpfs OPTS add tmpfs mount options, e.g. size - -v, --verbose verbose mode - -examples: - tmpoverlay / /new_root # make a thin copy of root - tmpoverlay /etc # make read-only /etc writable - tmpoverlay /a /b /c /merged # merge /a, /b, /c, and a fresh tmpfs - tmpoverlay / # USE WITH CAUTION, see docs -EOF - exit "$1" -} - -log() { - logn "$@" - printf '\n' >&2 -} - -logn() { - # not equivalent to printf "tmpoverlay: $@" - printf 'tmpoverlay: ' >&2 - printf "$@" >&2 -} - -logv() { - [ -z "$verbose" ] || log "$@" -} - -logvn() { - [ -z "$verbose" ] || logn "$@" -} - -cmdv() { - logv '%s ' "$@" - "$@" -} - -unset tmpdir -die() { - r=$? - [ "$r" != 0 ] || r=1 - [ "$#" = 0 ] || log "$@" - [ -z "$tmpdir" ] || { exec 9>&-; wait; } - exit $r -} - -canon() { - if [ -n "$no_canon" ]; then - printf '%s\n' "$1" - else - realpath "$1" - fi -} - -my_getopt() { - getopt \ - -l no-canonicalize \ - -l help \ - -l overlayfs: \ - -l no-mtab \ - -l mount-name: \ - -l tmpfs: \ - -l verbose \ - -n tmpoverlay \ - -- \ - cho:nN:t:v \ - "$@" -} - -args=$(my_getopt "$@") || usage 1 -eval set -- "$args" -unset args - -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 0;; - -o|--overlayfs) - [ -n "$2" ] && extra_ovl_opts="$extra_ovl_opts,$2" - shift 2 - ;; - -n|--no-mtab) no_mtab=-n; shift;; - -N|--mount-name) mount_name=$2; shift 2;; - -t|--tmpfs) - [ -n "$2" ] && tmpfs_opts="${tmpfs_opts:+$tmpfs_opts,}$2" - shift 2 - ;; - -v|--verbose) verbose=-v; shift;; - --) shift; break;; - *) die "getopt failure" - esac -done - -[ $# != 0 ] || usage 1 - -unset lowerdir -while [ "$#" != 1 ]; do - d=$(canon "$1") - if [ -h "$d" ] || ! [ -d "$d" ]; then - die 'source "%s" is not a directory' "$d" - fi - lowerdir=${lowerdir+:}$d - shift -done - -dest=$(canon "$1") -[ -d "$dest" ] || die 'destination "%s" is not a directory' "$dest" -[ "$dest" != / ] || log 'overmounting root, use with caution' - -[ -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 and re-raising signals which is annoying in shell -( - cd "$tmpdir" || die - trap '' INT || 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="$tmpdir/work" -tmpmnt="$tmpdir/tmpmnt" -logv 'creating dirs' -mkdir "$upperdir" "$workdir" "$tmpmnt" || die - -ovl_opts="lowerdir=$lowerdir,upperdir=$upperdir,workdir=$workdir" -logv 'testing overlay options' -mount -n -t overlay -o "$ovl_opts" overlay "$tmpmnt" || die "overlayfs is not supported" -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" || die -fi -chk_ovl_opt() { - if [ -n "$2" ]; then - case ",$ovl_opts," in - *",$1=$2,"*) return 0 - esac - [ "$2" = on ] && val=Y || val=N - else - val=Y - fi - f=/sys/module/overlay/parameters/$1 - [ -e "$f" ] && [ "$(cat "$f")" = "$val" ] -} -try_ovl_opt() { - # returns 0 iff option is/gets enabled - case ",$ovl_opts," in - *",$1=off,"*) return 1;; - *",$1[=,]"*) return 0 - esac - if chk_ovl_opt "$1"; then - logv 'not checking %s' - return - fi - logvn 'trying %s... ' "$1${2+=$2}" - new_ovl_opts="$ovl_opts,$1${2+=$2}" - if ! cmdv mount -n -t overlay -o "$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 - mkdir "$upperdir" "$workdir" || die - ovl_opts="$new_ovl_opts" -} -try_ovl_opt index on -# redirect_dir and metacopy are unsafe with untrusted non-bottom layers -# nfs_export conflicts with metacopy -[ "${lowerdir#*:}" = "$lowerdir" ] && \ - ! chk_ovl_opt userxattr on && \ - try_ovl_opt redirect_dir on && \ - { chk_ovl_opt nfs_export on || try_ovl_opt metacopy on; } -try_ovl_opt volatile - -logv 'copying lowerdir owner/perms to upperdir' -lastlowerdir=${lowerdir##*:} -# stat -c isn't posix, but ls is -ls=$(ls -dn "$lastlowerdir/.") || 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" "$upperdir" || die -# -m - covers ACLs (system.posix_acl_access) and file caps -# (security.capability). theoretically someone might have get/setcap and/or -# get/setfacl but not get/setxattr, but this is unlikely since libcap/acl -# require attr. -logv 'copying root xattrs' -if attrs=$(cd "$lastlowerdir" && getfattr -d -m - . 2>/dev/null); then - if [ -n "$attrs" ]; then - printf '%s\n' "$attrs" | (cd "$upperdir"; setfattr --restore=-) || die - fi -else - log 'getfattr failed, skipping xattrs/ACLs' -fi - -logv 'mounting overlay' -# shellcheck disable=SC2086 -cmdv mount $no_canon $no_mtab $verbose -t overlay -o "$ovl_opts" "${mount_name-overlay}" "$dest" || die -exec 9>&- -wait || die -logv 'done' |