With Red Hat Enterprise Linux, OpenLDAP uses Sleepycat
Software's Berkeley DB system as its on-disk storage format for
directories. Earlier versions of OpenLDAP used GNU Database Manager (gdbm). For this reason, before upgrading an LDAP
implementation to Red Hat Enterprise Linux 4, original LDAP data
should first be exported before the upgrade, and then reimported
afterwards. This can be achieved by performing the following
Before upgrading the operating system, run the command
/usr/sbin/slapcat -l ldif-output. This outputs an LDIF file
called ldif-output containing the entries from
the LDAP directory.
Upgrade the operating system, being careful not to reformat the
partition containing the LDIF file.
Re-import the LDAP directory to the upgraded Berkeley DB format
by executing the command /usr/sbin/slapadd -l