<appendix> <title>Troubleshooting</title> <sect1> <title>Database hangs</title> <para> If Nix or Fix appear to hang immediately after they are started, Nix's database is probably <quote>wedged</quote>, i.e., some process died while it held a lock on the database. The solution is to ensure that no other processes are accessing the database and then run the following command: </para> <screen> $ db_recover -e -h <replaceable>prefix</replaceable>/var/nix/db</screen> <para> Here, <replaceable>prefix</replaceable> should be replaced by Nix's installation prefix. </para> </sect1> <sect1> <title>Database logfile removal</title> <para> Every time a Nix database transaction takes place, Nix writes a record of this transaction to a <emphasis>log</emphasis> in its database directory to ensure that the operation can be replayed in case of a application or system crash. However, without manual intervention, the log grows indefinitely. Hence, unused log files should be deleted periodically. This can be accomplished using the following command: </para> <screen> $ rm `db_archive -a -h <replaceable>prefix</replaceable>/var/nix/db`</screen> </sect1> </appendix> <!-- local variables: sgml-parent-document: ("book.xml" "appendix") end: -->