Backup strategies largely depend on the amount of change in the database and how much of that change an administrator might be willing to lose in a catastrophic failure. There are two basic methods that can be used:
1. Backup the Berkeley database itself and periodically back up the transaction log files:
Berkeley DB produces transaction logs that can be used to reconstruct changes from a given point in time. For example, if an administrator were willing to only lose one hour's worth of changes, they could take down the server in the middle of the night, copy the Berkeley database files offsite, and bring the server back online. Then, on an hourly basis, they could force a database checkpoint, capture the log files that have been generated in the past hour, and copy them offsite. The accumulated log files, in combination with the previous database backup, could be used with db_recover to reconstruct the database up to the time the last collection of log files was copied offsite. This method affords good protection, with minimal space overhead.
2. Periodically run slapcat and back up the LDIF file:
Slapcat can be run while slapd is active. However, one runs the risk of an inconsistent database- not from the point of slapd, but from the point of the applications using LDAP. For example, if a provisioning application performed tasks that consisted of several LDAP operations, and the slapcat took place concurrently with those operations, then there might be inconsistencies in the LDAP database from the point of view of that provisioning application and applications that depended on it. One must, therefore, be convinced something like that won't happen. One way to do that would be to put the database in read-only mode while performing the slapcat. The other disadvantage of this approach is that the generated LDIF files can be rather large and the accumulation of the day's backups could add up to a substantial amount of space.
You can use slapcat(8) to generate an LDIF file for each of your slapd(8) back-bdb or back-hdb databases.
slapcat -f slapd.conf -b "dc=example,dc=com"
For back-bdb and back-hdb, this command may be ran while slapd(8) is running.
MORE on actual Berkeley DB backups later covering db_recover etc.