Added generic btrfs backups script

Signed-off-by: kitzman <kitzman@disroot.org>

scripts/generic_btrfs_backups/btrfs_backups.sh

@@ -0,0 +1,125 @@
+#!/bin/sh
+
+set -e
+
+backup_filename=".snapshot-$(date -I)"
+
+# runtime
+progname=$(basename $0)
+
+if [[ "$progname" != backup\.* ]]; then
+    echo "malformed name"
+    exit 1
+fi
+
+jobname=${progname:7}
+
+# configuration
+. /etc/conf.d/backup.$jobname
+
+logger_ident="${logger_ident:-backups}"
+backup_retency="${backup_retency:-10}"
+backup_qgroupid="${backup_qgroupid:-}"
+
+if [ -z "$target_backups_path" ]; then
+    echo "target_backups_path not set!"
+fi
+
+if [ -z "$source_storage_path" ]; then
+    echo "source_storage_path not set!"
+fi
+
+# utils & sanity checks
+
+function log() { echo $@; logger -t $logger_ident $@; }
+
+if [ ! -d "$target_backups_path" ]; then
+	log "$target_backups_path does not exist"
+	exit 1
+fi
+
+if [ ! -d "$source_storage_path" ]; then
+	log "$source_storage_path does not exist"
+	exit 1
+fi
+
+parent_backup=$(find $source_storage_path -maxdepth 1 -type d -name ".snapshot*")
+
+if [ ! -z "$parent_backup" ]; then
+    parent_backup=$(basename $parent_backup)
+fi
+
+#
+# Removing old backups
+#
+
+log "removing old backups from $target_backups_path"
+
+for backup_vol in $(find $target_backups_path -maxdepth 1 -type d \
+			 -name ".snapshot*" | \
+			sort | head -n $backup_retency); do
+    
+    log "removing $backup_vol"
+    backup_volid=$(btrfs sub list $target_backups_path | \
+		       grep $backup_vol | awk '{print $1}')
+    btrfs sub del $target_backups_path/$backup_vol
+
+    qgroup_id="0/$backup_volid"
+
+    btrfs qgroup destroy $qgroup_id || log "could not find qgroup $qgroup_id"
+done
+
+#
+# Create a new local snapshot
+#
+
+log "creating an interim backup in $source_storage_path"
+btrfs subvolume snapshot -r \
+	$source_storage_path \
+	$source_storage_path/$backup_filename
+
+#
+# Send it
+#
+
+log "sending backups from $source_storage_path to $target_backups_path"
+
+if [ ! -z "$parent_backup" ]; then
+    log "...with parent"
+    btrfs send \
+	  -p $source_storage_path/$parent_backup \
+	  $source_storage_path/$backup_filename | \
+	btrfs receive $target_backups_path/
+else
+    log "... without parent"
+    
+    btrfs send $source_storage_path/$backup_filename | \
+	btrfs receive $target_backups_path/
+fi
+
+if [ ! -z "$backup_qgroupid" ]; then
+    log "assigning qgroup $backup_qgroupid"
+    backup_volid=$(btrfs sub list $target_backups_path | \
+		       grep $backup_filename | awk '{print $1}')
+
+    btrfs qgroup assign --rescan "0/$backup_volid" "$backup_qgroupid" $target_backups_path
+fi
+
+#
+# Remove parent backup
+#
+
+log "removing old backups from $source_storage_path"
+
+if [ ! -z "$parent_backup" ]; then
+    btrfs subvolume delete $source_storage_path/$parent_backup
+fi
+
+#
+# Final sync
+#
+
+log "sync-ing and exiting"
+
+btrfs subvolume sync $source_storage_path
+btrfs subvolume sync $target_backups_path