If Nix or Fix appear to hang immediately after they are started, Nix's database is probably wedged, 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: $ db_recover -e -h prefix/var/nix/db Here, prefix should be replaced by Nix's installation prefix. Every time a Nix database transaction takes place, Nix writes a record of this transaction to a log 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: $ rm `db_archive -a -h prefix/var/nix/db`