So I’ve resisted the idea of Linux image backups for a while. After all, one can just backup all the files, right? True, even with Linuxs fast file access this might take a bit longer than doing an image backup if one has a a lot of files and one wants to back them all up…

Image backups also make backups and restores a lot easier. One doesn’t have to think about what to backup, instead it’s just the whole thing. When restoring, it’s just one step: Copy back the volume.

Advantages:

• Everything is backed up
• Content does not affect backup or restore performance (e.g. many small files don’t slow down backups and restores)
• 1:1 backups and restores of volumes

Disadvantages:

• Can’t select subset to backup (e.g. exclude temporary file data)
• Can’t migrate to different file system on restore
• File level deduplication doesn’t work
• E.g. defragmentation causes changes to backup

The following are step-by-step instructions on how to backup a Linux VPS.

Backup VPS (Step-by-step)

Assumption: VPS is running Debian 10/buster. 2.5.x server + client is used.

1. Add new client on server web interface:

2. Add active/Internet client

3. Copy & paste Linux client installation command and follow setup:

4. Reboot client/VPS (if not using dattobd)

5. Create image backup (“C” gets automatically translated to the Linux root volume)

Restore VPS (Step-by-step)

1. Browse to image backup in “Backups” tab on web interface

2. Click on restore Linux image

3. Copy & paste into new Debian 10/buster instance and follow instructions:

I’ve got a Xen server which runs a couple of Linux and Windows VMs. The VMs are stored in LVM volumes on a LVM volume group which is on a bcache device. The bcache device consists of a mirrored SSD pair (using mdraid) as cache and a mirrored HDD pair (also using mdraid) as backing storage. The SSD caching gives a nice performance boost, but nowadays I would go with SSD storage only, because bcache caused some problems (did not play nice with udev during boot).
The Windows VMs are backed up by installing the UrBackup client in the VMs. To restore I’d need to boot the restore CD in Xen or restore the Windows images via command line in the hypervisor.
The Linux VMs are backed up at hypervisor level in the Xen dom0 (which is Debian in this case) using LVM snapshots. To create and remove LVM snapshots I have following snapshot creation and removal script (the volume group on which the volumes are is mirror-vg).

Snapshot creation script at /usr/local/etc/urbackup/create_filesystem_snapshot:

#!/bin/bash
set -e
SNAP_UID=$1
VOLNAME="$5"
VGNAME="mirror-vg"
if [[ $VOLNAME == "" ]]; then
        echo "No volume name specified"
        exit 1
fi
if [[ $VOLNAME == "other-data" ]]; then
        VGNAME="data2-vg"
fi
if [[ $SNAP_UID == "" ]]; then
        echo "No snapshot uid specified"
        exit 1
fi
export LVM_SUPPRESS_FD_WARNINGS=1
lvcreate -l100%FREE -s -n $SNAP_UID /dev/$VGNAME/$VOLNAME
SUCCESS=0
trap 'test $SUCCESS = 1 || lvremove -f /dev/$VGNAME/$SNAP_UID' EXIT
mkdir -p /mnt/urbackup_snaps/${SNAP_UID}
mount -o ro /dev/$VGNAME/$SNAP_UID /mnt/urbackup_snaps/${SNAP_UID}
SUCCESS=1
echo "SNAPSHOT=/mnt/urbackup_snaps/$SNAP_UID"
exit 0

Snapshot removal script at /usr/local/etc/urbackup/remove_filesystem_snapshot:

#!/bin/bash
set -e
SNAP_UID=$1
SNAP_MOUNTPOINT="$2"
if [[ $SNAP_UID == "" ]]; then
        echo "No snapshot uid specified"
        exit 1
fi
if [[ "$SNAP_MOUNTPOINT" == "" ]]; then
        echo "Snapshot mountpoint is empty"
        exit 1
fi
if ! test -e $SNAP_MOUNTPOINT; then
        echo "Snapshot at $SNAP_MOUNTPOINT was already removed"
        exit 0
fi
if ! df -T -P | egrep "${SNAP_MOUNTPOINT}\$" > /dev/null 2>&1; then
        echo "Snapshot is not mounted. Already removed"
        rmdir "${SNAP_MOUNTPOINT}"
        exit 0
fi
if lsblk -r --output "NAME,MOUNTPOINT" --paths > /dev/null 2>&1; then
        VOLNAME=`lsblk -r --output "NAME,MOUNTPOINT" --paths | egrep " ${SNAP_MOUNTPOINT}\$" | head -n 1 | tr -s " " | cut -d" " -f1`
else
        VOLNAME=`lsblk -r --output "NAME,MOUNTPOINT" | egrep " ${SNAP_MOUNTPOINT}\$" | head -n 1 | tr -s " " | cut -d" " -f1`
        VOLNAME="/dev/mapper/$VOLNAME"
fi
if [ "x$VOLNAME" = x ]; then
    echo "Could not find LVM volume for mountpoint ${SNAP_MOUNTPOINT}"
    exit 1
fi
if [ ! -e "$VOLNAME" ]; then
    echo "LVM volume for mountpoint ${SNAP_MOUNTPOINT} does not exist"
    exit 1
fi
echo "Unmounting $VOLNAME at /mnt/urbackup_snaps/${SNAP_UID}..."
if ! umount /mnt/urbackup_snaps/${SNAP_UID}; then
        sleep 10
        umount /mnt/urbackup_snaps/${SNAP_UID}
fi
rmdir "${SNAP_MOUNTPOINT}"
echo "Destroying LVM snapshot $VOLNAME..."
export LVM_SUPPRESS_FD_WARNINGS=1
lvremove -f "$VOLNAME"

The snapshot scripts are specified via the file /usr/local/etc/urbackup/snapshot.cfg:

create_filesystem_snapshot=/usr/local/etc/urbackup/create_filesystem_snapshot
remove_filesystem_snapshot=/usr/local/etc/urbackup/remove_filesystem_snapshot
volumes_mounted_locally=0

Then I have a virtual client for each LVM volume that needs to be backed up. I have put those virtual clients in a settings group with the default path to backup “/|root/require_snapshot”.

For restore I need to recreate the LVM volume. Create a file system on it (e.g. with mkfs.ext4) mount it in the hypervisor and then restore via.

urbackupclientctl restore-start --virtual-client VOLUMENAME -b last –map-from / --map-to /mnt/localmountpoint