Problem: Incorrect MDB Max Size Warning during upgrade to UCS 5.2

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Problem

While preparing an upgrade from UCS 5.0-x to UCS 5.2, the pre-upgrade check reports critical warnings related to the LMDB database size:

root@ucs52:~# ./check.sh update_check_mdb_max_size

Starting ./check.sh (Di 10. Feb 14:25:14 CET 2026):

Metric univention_listener_mdb_size_used_ratio has value 146.96% and is above the critical limit (90%).
Metric univention_slapd_mdb_size_used_ratio has value 380.87% and is above the critical limit (90%).
Metric univention_slapd_translog_mdb_size_used_ratio has value 434.81% and is above the critical limit (90%).

Proceeding without raising the maxsize limit may lead to a failure during the upgrade.
See https://help.univention.com/t/how-to-properly-configure-lmdb-maxsize-in-ldap/24558 and
https://help.univention.com/t/how-to-clean-up-the-translog-from-a-certain-point-in-time/18872
If you are sure this warning can be ignored, you may set update52/ignore_mdb_maxsize_checks to yes.

Root Cause

This behavior is caused by a known issue in the pre-update check script, which may report incorrect MDB usage values.

The problem is tracked in the following bug report:
https://forge.univention.org/bugzilla/show_bug.cgi?id=58886

Investigation

The current configuration and actual disk usage were reviewed:

root@ucs52:~# ucr get ldap/database/mdb/maxsize
2147483648
root@ucs52:~# du -sh /var/lib/univention-ldap/ldap
108M /var/lib/univention-ldap/ldap

Despite the warning, the actual LDAP database size is relatively small.

To validate the real MDB usage, the following Nagios plugin was executed:

root@ucs52:~# /usr/lib/nagios/plugins/check_univention_slapd_mdb_maxsize

Output:

SLAPD MDB OK: Database /var/lib/univention-ldap/ldap operational (in
fact 3%)
Database /var/lib/univention-ldap/translog operational (in fact 4%)

Additionally, the translog size was checked:

root@ucs52:~# du -h /var/lib/univention-ldap/translog
90M /var/lib/univention-ldap/translog

The comparison with the Nagios check is exactly what was needed.
The output reflects the actual current state and therefore it is not critical.

Solution

Please update the system to the latest erratum level 1385 for UCS 5.0-10 and perform a full reboot, as kernel updates are delivered with the errata.

You are welcome to use the following command:

univention-upgrade --updateto=5.0-10 --ignoressh --ignoreterm && reboot

Afterwards, run the pre-update-check using the script below. It should no longer report any errors regarding mdb_maxsize:
https://docs.software-univention.de/release-notes/5.2-0/en/index.html#script-to-check-for-known-update-issues

After updating to erratum level 1385 the issue seems to be resolved.

Output:

root@ucs52:~# apt-key verify pre-update-checks-5.2-0{.gpg,} && bash
pre-update-checks-5.2-0
gpgv: Signature made Di 16 Dez 2025 13:25:24 CET
gpgv:                using RSA key C882B6F1F7229D9A
gpgv: Good signature from "Univention Corporate Server 5.2
<packages@univention.de>"

Starting pre-update-checks-5.2-0 (Di 17. Feb 13:55:43 CET 2026):
Checking auth_faillog ...                         OK
Checking blocking_apps ...                        OK
Checking disk_space ...                           OK
Checking docker_storage_driver ...                OK
Checking failed_ldif ...                          OK
Checking for_postgresql96 ...                     OK
Checking hold_packages ...                        OK
Checking keycloak_migration ...                   OK
Checking ldap_connection ...                      OK
Checking ldap_schema ...                          OK
Checking legacy_objects ...                       OK
Checking master_version ...                       OK
Checking mdb_max_size ...                         OK
Checking min_version ...                          OK
Checking minimum_ucs_version_of_all_systems_in_domain ... OK
Checking openldap_bdb ...                         OK
Checking overwritten_umc_templates ...            OK
Checking package_status ...                       OK
Checking role_package_removed ...                 OK
Checking selinux_deactivated ...                  OK
Checking slapd_on_member ...                      OK
Checking system_date_too_old ...                  OK
Checking user_country_mapping ...                 OK
Checking valid_machine_credentials ...            OK
Checking verify_translog_schema ...               OK

Summary

  • The MDB max size warning during the pre-upgrade check can be misleading due to a known bug.
  • The Nagios plugin provides the correct and reliable state.
  • Updating to UCS 5.0-10 erratum 1385 resolves the issue.
  • After the update, the pre-upgrade check completes successfully without MDB warnings.

Additional