Plesk update or upgrade failed: ERROR while trying to backup MySQL database

Symptoms

Plesk update or upgrade failed:

PLESK_ERROR: chown: changing ownership of `/var/lib/psa/dumps/mysql.preupgrade.11.5.30-11.5.30.20131211-190722.dump.gz': Operation not permitted

or:

PLESK_ERROR: ... touch: setting times of '/mnt/opendrive/webserver/Backup/mysql.preupgrade.17.5.3-17.5.3.20170921-194900.dump.gz': No such file or directory
ERROR while trying to backup MySQL database
Check the error reason(see log file: /var/log/plesk/install/plesk_17.5.3_installation.log), fix and try again ERROR: An error occurred during performing of installation PREP actions (see log for details). Installation was rolled back.
Warning! Not all packages were installed.
Please check if your system services are operable.
Please resolve this issue and try to install the packages again.
If you cannot resolve the issue on your own, contact product technical support for assistance.

or:

PLESK_ERROR: EMERGENCY: Unable to write in the /backup_custom directory. The upgrade procedure will fail. Check that the folder exists and you have write permissions for it, and repeat upgrading.

Backup location was customized:

# grep -i dump /etc/psa/psa.conf
DUMP_D /backup_custom
DUMP_TMP_D /backup_custom/tmp

It's not possible to create a new file on this location:

# touch /backup_custom/test.txt
touch: setting times of ‘/backup_custom/test.txt’: No such file or directory

Cannot change the backup directory permissions because it is mounted in read-only mode:

# chmod 750 /backup_custom
chmod: changing permissions of /backup_custom: Read-only file system

# mount | grep backup
/dev/sdc1 on /backup_custom type ext4 (ro,relatime,discard,data=ordered,_netdev)

Cause

During the upgrade process Plesk creates databases (psa, horde) dumps. Prior to dumping database, it corrects permissions for files in the backup directory. If backup directory is located on NFS share or external drive, Plesk fails to change permissions there and create a backup.

Resolution

1. Login to the server over SSH

2. Back up /etc/psa/psa.conf configuration file

   # cp /etc/psa/psa.conf{,.orig}

3. Change the backup location directory to a default one:

   # grep -n DUMP /etc/psa/psa.conf
   DUMP_D /var/lib/psa/dumps
   DUMP_TMP_D /tmp

4. Make sure both directories have the same permissions as:
   

   # ls -ld /var/lib/psa/dumps
   drwxr-x--- 6 psaadm psaadm 20480 Sep 22 02:46 /var/lib/psa/dumps
   # ls -ld /tmp
   drwxrwxrwt 29 root root 20480 Sep 22 03:01 /tmp

5. Complete the update or upgrade in Plesk > Tools&Settings > Updates & Upgrades

6. When upgrade process is finished, revert the changes made in /etc/psa/psa.conf

Workaround for remote NFS share used as a backup location:

1. Login to the server over SSH

2. Open /etc/exports and set 'no_root_squash' option to the share configuration string. For example:

CONFIG_TEXT: /srv/nfs 203.0.113.2/32(rw,sync,sec=sys,no_root_squash)

3. Apply the configuration settings:

# exportfs -avr