23 lines
944 B
Bash
23 lines
944 B
Bash
#!/usr/bin/env bash
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# The upgrade coordinator holds FD 9 for the complete install/check/backup cycle.
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# Child tools may reuse that SAME open file description, never bypass the lock.
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acquire_backup_lock() {
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[[ $LOCKFILE == /* && ! -L $LOCKFILE ]] || { echo 'Unsafe lock path' >&2; return 1; }
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if [[ -e $LOCKFILE ]]; then
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[[ -f $LOCKFILE && ! -s $LOCKFILE && $(stat -c %u "$LOCKFILE") == 0 ]] || { echo 'Unsafe existing lock file' >&2; return 1; }
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fi
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if [[ ${APP_BACKUP_INHERIT_LOCK:-0} == 1 ]]; then
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[[ -e /proc/self/fd/9 && $(stat -Lc '%d:%i' /proc/self/fd/9) == "$(stat -Lc '%d:%i' "$LOCKFILE")" ]] || {
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echo 'Inherited lock descriptor does not match configured lock' >&2; return 1;
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}
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else
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exec 9>"$LOCKFILE" || return 1
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fi
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local lock_code
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flock -E "${1:-1}" -n 9 || {
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lock_code=$?
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echo "Another backup/restore/update holds $LOCKFILE, or the lock is unavailable" >&2
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return "$lock_code"
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}
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}
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