Backing up the KVM host Using Snapshot-Based Backup

6.10.1 Backing up the KVM host Using Snapshot-Based Backup

This procedure describes how to take a snapshot-based backup of the KVM host.

The values shown in the following steps are examples and you may need to substitute different values to match your situation.

All steps must be performed as the root user.

Prepare a destination to hold the backup.

The destination should reside outside of the local machine, such as a writable NFS location, and be large enough to hold the backup. For non-customized partitions, the space needed for holding the backup is approximately 50 GB.
You can use the following commands to prepare a backup destination using NFS.
```
# mkdir -p /root/remote_FS
# mount -t nfs -o rw,intr,soft,proto=tcp,nolock ip_address:/nfs_location/ /root/remote_FS
```
In the mount command, ip_address is the IP address of the NFS server, and nfs_location is the NFS location holding the backups.
Remove the LVDoNotRemoveOrUse logical volume.
The logical volume /dev/VGExaDb/LVDoNotRemoveOrUse is a placeholder to make sure there is always free space available to create a snapshot.

Use the following script to check for the existence of the LVDoNotRemoveOrUse logical volume and remove it if present.
```
lvm lvdisplay --ignorelockingfailure /dev/VGExaDb/LVDoNotRemoveOrUse
if [ $? -eq 0 ]; then 
  # LVDoNotRemoveOrUse logical volume exists. 
  lvm lvremove -f /dev/VGExaDb/LVDoNotRemoveOrUse 
  if [ $? -ne 0 ]; then 
    echo "Unable to remove logical volume: LVDoNotRemoveOrUse. Do not proceed with backup." 
  fi
fi
```
If the LVDoNotRemoveOrUse logical volume does not exist, then do not proceed with the remaining steps and determine the reason.

Determine the active system volume.

You can use the imageinfo command and examine the device hosting the active system partition.

# imageinfo

Kernel version: 4.14.35-1902.5.1.4.el7uek.x86_64 #2 SMP Wed Oct 9 19:29:16 PDT 2019 x86_64
Image kernel version: 4.14.35-1902.5.1.4.el7uek
Image version: 19.3.1.0.0.191018
Image activated: 2019-11-04 19:18:32 -0800
Image status: success
Node type: KVMHOST
System partition on device: /dev/mapper/VGExaDb-LVDbSys1

In the imageinfo output, the system partition device ends with the name of the logical volume supports the active root (/) file system. Depending on the system image that is in use, the logical volume name is LVDbSys1 or LVDbSys2. Likewise, the logical volume for the /var file system is either LVDbVar1 or LVDbVar2.

You can also confirm the active devices by using the df -hT command and examining the output associated with the root (/) and /var file systems. For example:

# df -hT
Filesystem                          Type      Size  Used Avail Use% Mounted on
devtmpfs                            devtmpfs  378G     0  378G   0% /dev
tmpfs                               tmpfs     755G  1.0G  754G   1% /dev/shm
tmpfs                               tmpfs     378G  4.8M  378G   1% /run
tmpfs                               tmpfs     378G     0  378G   0% /sys/fs/cgroup
/dev/mapper/VGExaDb-LVDbSys1        xfs        15G  7.7G  7.4G  52% /
/dev/sda1                           xfs       510M  112M  398M  22% /boot
/dev/sda2                           vfat      254M  8.5M  246M   4% /boot/efi
/dev/mapper/VGExaDb-LVDbHome        xfs       4.0G   33M  4.0G   1% /home
/dev/mapper/VGExaDb-LVDbVar1        xfs       2.0G  139M  1.9G   7% /var
/dev/mapper/VGExaDb-LVDbVarLog      xfs        18G  403M   18G   3% /var/log
/dev/mapper/VGExaDb-LVDbVarLogAudit xfs      1014M  143M  872M  15% /var/log/audit
/dev/mapper/VGExaDb-LVDbTmp         xfs       3.0G  148M  2.9G   5% /tmp
/dev/mapper/VGExaDb-LVDbOra1        xfs       100G   32G   69G  32% /u01
tmpfs                               tmpfs      76G     0   76G   0% /run/user/0

The remaining examples in the procedure use LVDbSys1 and LVDbVar1, which is consistent with the above imageinfo and df output. However, if the active image is using LVDbSys2, then modify the examples in the following steps to use LVDbSys2 instead of LVDbSys1, and LVDbVar2 instead of LVDbVar1.

Take snapshots of the logical volumes on the server.

Depending on the active system partition identified in the previous step, remember to use either LVDbSys1 or LVDbSys2 to identify the logical volume for the root (/) file system, and likewise use either LVDbVar1 or LVDbVar2 to identify the logical volume for the /var file system.

# lvcreate -L1G -s -c 32K -n root_snap /dev/VGExaDb/LVDbSys1
# lvcreate -L1G -s -c 32K -n home_snap /dev/VGExaDb/LVDbHome
# lvcreate -L1G -s -c 32K -n var_snap /dev/VGExaDb/LVDbVar1
# lvcreate -L1G -s -c 32K -n varlog_snap /dev/VGExaDb/LVDbVarLog
# lvcreate -L1G -s -c 32K -n audit_snap /dev/VGExaDb/LVDbVarLogAudit
# lvcreate -L1G -s -c 32K -n tmp_snap /dev/VGExaDb/LVDbTmp

Label the snapshots.

# xfs_admin -L DBSYS_SNAP /dev/VGExaDb/root_snap
# xfs_admin -L HOME_SNAP /dev/VGExaDb/home_snap
# xfs_admin -L VAR_SNAP /dev/VGExaDb/var_snap
# xfs_admin -L VARLOG_SNAP /dev/VGExaDb/varlog_snap
# xfs_admin -L AUDIT_SNAP /dev/VGExaDb/audit_snap
# xfs_admin -L TMP_SNAP /dev/VGExaDb/tmp_snap

Mount the snapshots.

Mount all of the snapshots under a common directory location; for example, /root/mnt.

# mkdir -p /root/mnt
# mount -t xfs -o nouuid /dev/VGExaDb/root_snap /root/mnt
# mkdir -p /root/mnt/home
# mount -t xfs -o nouuid /dev/VGExaDb/home_snap /root/mnt/home
# mkdir -p /root/mnt/var
# mount -t xfs -o nouuid /dev/VGExaDb/var_snap /root/mnt/var
# mkdir -p /root/mnt/var/log
# mount -t xfs -o nouuid /dev/VGExaDb/varlog_snap /root/mnt/var/log
# mkdir -p /root/mnt/var/log/audit
# mount -t xfs -o nouuid /dev/VGExaDb/audit_snap /root/mnt/var/log/audit
# mkdir -p /root/mnt/tmp
# mount -t xfs -o nouuid /dev/VGExaDb/tmp_snap /root/mnt/tmp

Back up the snapshots.

Use the following commands to write a backup to your prepared NFS backup destination as a compressed archive file.

# cd /root/mnt
# tar --acls --xattrs --xattrs-include=* --format=pax -pjcvf /root/remote_FS/myKVMbackup.tar.bz2 * /boot > /tmp/backup_tar.stdout 2> /tmp/backup_tar.stderr

Check the /tmp/backup_tar.stderr file for any significant errors.
Errors about failing to archive open sockets, and other similar errors, can be ignored.

Unmount and remove all of the snapshots.

# cd /
# umount /root/mnt/tmp
# umount /root/mnt/var/log/audit
# umount /root/mnt/var/log
# umount /root/mnt/var
# umount /root/mnt/home
# umount /root/mnt
# lvremove /dev/VGExaDb/tmp_snap
# lvremove /dev/VGExaDb/audit_snap
# lvremove /dev/VGExaDb/varlog_snap
# lvremove /dev/VGExaDb/var_snap
# lvremove /dev/VGExaDb/home_snap
# lvremove /dev/VGExaDb/root_snap

Unmount the NFS backup destination.
```
# umount /root/remote_FS
```
Remove the mount point directories that you created during this procedure.
```
# rm -r /root/mnt
# rmdir /root/remote_FS
```
Recreate the /dev/VGExaDb/LVDoNotRemoveOrUse logical volume.
```
# lvm lvcreate -n LVDoNotRemoveOrUse -L2G VGExaDb -y
```

Parent topic: Backing up the KVM host and Guests