<appendix> <title>Troubleshooting</title> <para>This section provides solutions for some common problems.</para> <sect1><title>Berkeley DB: <quote>Cannot allocate memory</quote></title> <para>Symptom: Nix operations (in particular the <command>nix-store</command> operations <option>--gc</option>, <option>--verify</option>, and <option>--clear-substitutes</option> — the latter being called by <command>nix-channel --update</command>) failing: <screen> $ nix-store --verify error: Db::del: Cannot allocate memory</screen> Possible solution: make sure that no Nix processes are running, then do: <screen> $ cd /nix/var/nix/db $ rm __db.00*</screen> </para> </sect1> </appendix>