After upgrading MariaDB to 10.5 Seafile stopped working. journalctl showed errors like the following for mariadb.service:

[Warning] Aborted connection 62 to db: 'seafile_ccnet-db' user: 'seafile' host: 'localhost' (Got an error reading communication packets)

Further investigation revealed the open files limit to be the root cause:

root@server:~# mysql -e "SHOW VARIABLES LIKE 'open_files_limit';"
| Variable_name    | Value |
| open_files_limit | 32768 |

To increase the limit the corresponding Systemd unit needs to be overriden using systemctl edit mariadb.service. This creates /etc/systemd/system/mariadb.service.d/override.conf:


Also, MariaDB needs a configuration modification, e.g. in /etc/mysql/mariadb.conf.d/77_tuning.conf:

open_files_limit = 65536