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NFS as backup target

It makes a lot of sense to store the backups from raspiBackup to a NAS and to use the NFS protocol for this purpose. The following describes how to configure this on a Synology. Of course, you can also use any other NAS as long as it supports NFS. A Raspberry can also be configured and used as an NFS server.

raspiBackup - Using NFS using the example of a Synology

Important: The partition on the NAS must be exported with no_root_squash, so that rsync can be used. In the UI, no-mapping must then be entered for squash must be entered.

Synology configuration

You must NOT activate NFS4 as shown in the screenshot! It must NFS3 must be used. I could not manage it with NFS4.

Synology NFS Configuration

Configuration of a Synology and the Raspberry to back up a rsync backup via NFS on a Synology

Essentially, the following steps must be carried out:

  1. Create a shared NFS folder on the Synology
  2. Mount the shared NFS folder on the Raspi in /etc/fstab.
  3. Install and configure raspiBackup via Installer (do not configure an automatic backup)
  4. Test the backup and restore from the command line
  5. Set up the regular backup in the crontab via Installer

It is recommended that you read the FAQ before starting, where the most important questions and answers about raspiBackup.

Create a shared NFS folder on the Synology

In DSM, Control Panel -> Shared Folder -> Create, create a shared folder shared folder e.g. with the name raspiBackups. You do not need a recycle bin not. The NFS permissions must be set as follows (Note: raspiBackup runs as root). Hostname or IP: Hostname or IP of the NFS client, e.g. 192.168.0.10. Privilege: read/write, squash: no assignment, Security: sys.

Entry of the shared NFs folder on the Raspi in the fstab

The following entry in /etc/fstab causes the Synology NFS folder to be mounted under the mountpoint /backup under the assumption that 192.168.0.11 is the Synology is:

192.168.0.11:/volume1/raspiBackups /backup nfs rw,nfsvers=3 0 0

**It is strongly recommended to use the mountpoint /backup and not e.g. /home/pi/backup or other directories **.

Manual mount of the shared NFS folder

Now you can check if the backup space on the Synology is shared with showmount -e 192.168.0.11. Then you can use sudo mount /backup to manually mount the NFS folder manually. With the above entry in /etc/fstab the automatically after every reboot, and a manual mount is no longer necessary. mount is no longer necessary.

Test the write access

You can now test the write access with sudo bash -c 'echo "Raspberry was here" > /backup/killroy.txt' and sudo cat /backup/killroy.txt. If there are problems, tips from experienced Synology users on Synology and raspiBackup.

Installation and configuration of raspiBackup

Install raspiBackup according to these instructions. Specify rsync as backup method and /backup as backup path. Do not configure the regular backup yet.

Test the backup and restore from the command line

Set up the regular backup in the installer

Call up the installer and configure the regular backup time.

Note on ACLs

ACLs can actually be backed up with NFS3. This works, for example, if you set up a Raspberry as an NFS server (see https://linux-tips-and-tricks.de). However, this does not work with a Synology - even if it uses NFS3.

An inquiry to Synology on 13.5.2022 provided the following answer:

Unfortunately, I have to inform you that both Linux ACL and setfacl are not supported by DSM. I would be pass this on as feedback to our development department as a function request.

Hints and tips from raspiBackup users who use a Synology as backup space

Note from Udo

Udo has described in the comment what you have to do so that the automount of the Synology to work when booting the Raspberry.

It has been reported several times that there can be problems with Synologies with hardlinks used by rsync when NFS4 is used. With

192.168.0.42:/backup /backup nfs rw,nfsvers=3 0 0

the NFS3 protocol is used so that the backup script runs successfully. Furthermore, softlinks with SMB are not supported unless at least SMB version 3 is used.

Note from Markus

My backup runs with raspiBackup in the following configuration:

  • Raspberry with Raspbian Wheezy
  • raspiBackup.sh, version 0.5.7.10e
  • Synology NAS DS213, with current DSM version

Synology NAS Share: /volume1/backup Synology NAS Share NFS rules: Hostname or IP: *, Privilege: Read/Write, Squash: No assignment Synology NAS Share permissions (console): d--------- 5 root root 4096 Dec 15 06:01 backup Raspberry Pi mountpoint: /media/nas-backup

Raspberry Pi fstab entries for NFS3 and NFS4

# Entry for the NAS backup, mount with NFS version 3
192.168.X.XXX:/volume1/backup /media/nas-backup nfs rw,nfsvers=3 0 0
# Entry for the NAS backup, mount with NFS version 4
#192.168.X.XXX:/volume1/backup /media/nas-backup nfs rw 0 0

Extract from raspiBackup.conf stored under /usr/local/etc/

cat /usr/local/etc/raspiBackup.conf
# path to store the backupfile
DEFAULT_BACKUPPATH="/media/nas-backup"
# how many backups to keep
DEFAULT_KEEPBACKUPS=4
# type of backup: dd, tar, xbmc or rsync
DEFAULT_BACKUPTYPE="rsync"

Notes from Alfred

Alfred got the following error message from rsync

rsync: chown "/mnt/nas/arami nta/araminta-rs ync-backup-2016 1029-190948/mmc blk0p1/overlays /.w1-gpio-overl ay.dtb.ansSC4" failed: Operation not permitted (1)"

Then he used the rsync command he found in the raspiBackup.log, the raspiBackup to create the backup in order to reproduce the problem and and to debug specifically without raspiBackup. Since he uses the -P mode mode, he had to execute the following commands first:

sudo mkdir /tmp/mmcblk0p1
sudo mount /dev/mmcblk0p1 /tmp/mmcblk0p1

He then accidentally made a mistake that led to the solution: This is the rsync command he executed:

rsync --exclude="/mnt/nas" --exclude=/proc/* --exclude=/lost found/* --exclude=/sys/* --exclude=/dev/* --exclude=/boot/* --exclude=/tmp/* --exclude=/run/* --exclude=mmcblk0p1/overlays/* --numeric-ids -aHAXx -v /tmp/mmcblk0p1 "/mnt/nas/test.backup"

This command worked without an error message. But it was because forgot to use 'sudo'. When the command was executed again with sudo the error message appeared again. IMHO this indicates an access problem on the Synology NAS. After changing the NFS permissions on the NAS from 'map all users to admin' to 'no mapping', bingo, it worked again with sudo. it also worked with sudo.

Note from Chris

A TAR backup was successfully created via NFS 4.1 on a QNAP NAS as follows.

Contents - /etc/fstab:

<NAS-IP/hostname>:/<share name> /backup nfs4 defaults,_netdev,noatime 0 2

QNAP NAS side (share):

Access right -> sync = "no wdelay"
Access right -> secure (Yes)
Host: IP from Raspi
Security: sys,
Squash option: read/write
Squash option: "Assign root user only"
Anonymous GID: guest
Anonymous UID: guest