Building the Aliases Database

Building the Aliases Database

At startup, sendmail automatically uses the ndbm library to process the /etc/aliases file into the files /etc/aliases.dir and /etc/aliases.pag. Using these files to resolve aliases improves performance.

To rebuild the DBM version of the database without restarting sendmail, execute this command:

newaliases

Executing this command is equivalent to giving sendmail the -bi flag:

/usr/lib/sendmail -bi

When building the DBM version of the database, sendmail checks the left-hand side of each entry to make sure that it is a local address. sendmail issues a warning for each entry in /etc/aliases with a non-local left-hand side. Such entries are not entered into the DBM version of the database.

If the NIS alias database is used with the local usr/lib/aliases database, the special "+:+" alias is entered into the DBM version of the database. If sendmail cannot find an alias in the DBM version of the database, it looks for the special "+:+" alias. If it finds the special alias, sendmail then queries the NIS alias database. This query permits you to change the global NIS alias database without having to rebuild the local alias database. However, the left-hand sides of the NIS alias are not checked by sendmail to ensure that they contain only local addresses.

If the configuration or the command line specifies the D option, sendmail will automatically try to rebuild the alias database when it is out of date.

sendmail rebuilds the alias database if either of the following conditions exists:

The DBM version of the database is mode 666.
sendmail is running setuid to root.

Auto-rebuild can be dangerous on heavily loaded stations with large alias files. If it takes more than five minutes to rebuild the database, there is a chance that several processes will start the rebuild process simultaneously.