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October 19, 2021 08:43
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Put this script at /sbin/mount.ovtmp . Script for tmpfs overlays. Put a line for mounting an "ovtmp" fs into fstab, and it'll use a tmpfs and overlayfs to mount over the target. Useful if the root is readonly, but changes need to be possible but don't need persistance.
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| #!/bin/sh | |
| set -e | |
| cleanup(){ | |
| set +e | |
| if [ -n "$tmp" ] | |
| then | |
| umount -l "$tmp" 2>/dev/null | |
| rmdir "$tmp" | |
| fi | |
| } | |
| die(){ | |
| echo "Usage: $0 name target" >&2 | |
| exit 1 | |
| } | |
| dir= | |
| name= | |
| options= | |
| i=0 | |
| while [ $# -gt 1 ] | |
| do | |
| arg="$1" | |
| shift | |
| case "$arg" in | |
| -o*) | |
| if [ "$arg" = -o ] | |
| then arg="$1"; shift | |
| else arg="${arg#-o}" | |
| fi | |
| options="$arg" | |
| ;; | |
| -*) die ;; | |
| *) | |
| i=$(expr $i + 1) | |
| case "$i" in | |
| 1) name="$arg" ;; | |
| 2) dir="$arg" ;; | |
| *) die ;; | |
| esac | |
| ;; | |
| esac | |
| done | |
| arg= | |
| if [ -z "$name" ] | |
| then name="ovtmp" | |
| fi | |
| if [ -z "$dir" ] | |
| then | |
| echo "Usage: $0 name target" | |
| exit 1 | |
| fi | |
| trap cleanup exit | |
| tmp=$(mktemp -d /tmp/.ovtmp.XXXXXX) | |
| mount -t tmpfs -o "$options" "$name.tmpfs" "$tmp" | |
| mkdir -p "$tmp/u" "$tmp/w" | |
| mount -t overlay "$name" -o lowerdir="$dir",upperdir="$tmp/u",workdir="$tmp/w" "$dir" |
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