c8396037db
Occasionally, the latest snapshot in the snapshots dir would get out of sync with the backup drive. Change the script to detect drift and fix it before performing a backup.
83 lines
3.0 KiB
Bash
Executable File
83 lines
3.0 KiB
Bash
Executable File
#!/bin/bash
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export SOURCE_DIR=${SOURCE_DIR:=/}
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# Fix basename / showing up as "/" -> change to "root"
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if [ $(basename $SOURCE_DIR) = / ]; then
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export SNAPSHOT_PREFIX=${SNAPSHOT_PREFIX:=root}
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else
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export SNAPSHOT_PREFIX=${SNAPSHOT_PREFIX:=$(basename $SOURCE_DIR)}
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fi
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# Set snapshot prefix based on basename
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export SNAPSHOT_TIME=$(date +"%y_%m_%d-%H.%M")
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export SNAPSHOT_NAME=$SNAPSHOT_PREFIX-$SNAPSHOT_TIME
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export SNAPSHOT_DIR=${SNAPSHOT_DIR:=/.snapshots}
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export LATEST=$SNAPSHOT_PREFIX-latest
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export BACKUP_DRIVE_MNT=${BACKUP_DRIVE_MNT:=/mnt/backup0}
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export BACKUP_DIR=${BACKUP_DIR:=/mnt/backup0/DucoBacktop}
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# Show snapshot settings
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echo "SOURCE_DIR: $SOURCE_DIR"
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echo "SNAPSHOT_PREFIX: $SNAPSHOT_PREFIX"
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echo "SNAPSHOT_TIME: $SNAPSHOT_TIME"
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echo "SNAPSHOT_NAME: $SNAPSHOT_NAME"
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echo "SNAPSHOT_DIR: $SNAPSHOT_DIR"
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echo "LATEST: $LATEST"
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echo "BACKUP_DRIVE_MNT: $BACKUP_DRIVE_MNT"
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echo "BACKUP_DIR: $BACKUP_DIR"
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# Sync latest backups
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# The "latest" symlinks can get out of sync for a variety of reasons,
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# including backups run while the disk is unplugged.
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# They must be kept in sync so that snapshots are sent with a parent
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# that actually exists on the backup drive
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#
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# In order to keep them in sync we'll do the following:
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# 1. Check the <backup>-latest on the backup drive matches
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# <backup>-latest in the snapshot directory
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# 2. If they don't match, assume the backup drive has the correct
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# snapshot. Replace the <backup>-latest symlink in the snapshots
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# directory with the one from the backup drive
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#
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# First check if the symlinks exist
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if [ -L $SNAPSHOT_DIR/$LATEST ] && [ -L $BACKUP_DIR/$LATEST ]
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then
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# Get the actual name of the latest backup
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LATEST_SNAPSHOT=$(basename $(readlink $SNAPSHOT_DIR/$LATEST))
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LATEST_BACKUP=$(basename $(readlink $BACKUP_DIR/$LATEST))
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# If the latest backups don't match
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if [ $LATEST_SNAPSHOT != $LATEST_BACKUP ]
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then
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echo "Detected drift. Synchronizing latest snapshot with backup. Set to $LATEST_BACKUP."
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# Remove and replace the snapshot directory's latest
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rm $SNAPSHOT_DIR/$LATEST
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ln -s $SNAPSHOT_DIR/$LATEST_BACKUP $SNAPSHOT_DIR/$LATEST
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fi
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fi
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# Create readonly snapshot
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btrfs subvolume snapshot -r $SOURCE_DIR $SNAPSHOT_DIR/$SNAPSHOT_NAME
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# Attempt to mount backup disk
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mount $BACKUP_DRIVE_MNT
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# Check if backup disk is mounted
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mountpoint $BACKUP_DRIVE_MNT
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if [ $? = 0 ]; then # backup drive mounted
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# If we have a latest, use it as the parent
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if [ -L $BACKUP_DIR/$LATEST ]; then
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btrfs send -p $SNAPSHOT_DIR/$LATEST $SNAPSHOT_DIR/$SNAPSHOT_NAME | btrfs receive $BACKUP_DIR
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else
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btrfs send $SNAPSHOT_DIR/$SNAPSHOT_NAME | btrfs receive $BACKUP_DIR
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fi
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# Update latest in backup dir
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rm -f $BACKUP_DIR/$LATEST
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ln -s $BACKUP_DIR/$SNAPSHOT_NAME $BACKUP_DIR/$LATEST
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else
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echo "Backup location $BACKUP_DRIVE_MNT not mounted. Snapshot $SNAPSHOT_NAME not synced"
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fi
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# Update latest in snapshot dir
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rm -f $SNAPSHOT_DIR/$LATEST
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ln -s $SNAPSHOT_DIR/$SNAPSHOT_NAME $SNAPSHOT_DIR/$LATEST
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