Let us take a closer look at the postfix error open database /etc/aliases.db. We can remove the error With the support of our Server management support services at Bobcares.

What does “fatal: open database /etc/aliases.db” mean?

The Berkeley DB library manages db files. The above error message might signify one of the following:

The present file lacks the specified file format. One of the following is the cause:

• Berkeley DB version 1 produced the file, and we are using version 2 or 3. (or vice versa).

Postfix expects “hash” format and the file was written in “btree” format (or vice versa).

To resolve the Postfix issue, run the following command as root:

newaliases.

This generates the aliases.db file in the Postfix-compatible format. Or the open database /etc/aliases.db error could be different. If the output of newaliases is a zero-length aliases.db file, we most likely have the following issue.

The setup postfix is done by using Berkeley DB version X #include files. It is linked against Berkeley DB version Y object library files. Here the X and Y are separate versions of the Berkeley DB library.

The solution in this case is to install the Berkeley DB library properly.  For example, RedHat version 7.0 by default uses the Berkeley DB version 3 object library. But in this case no /usr/include/db.h file is present. To construct Postfix correctly, we must first install the db3-devel package. Including the file db.h and linking with -ldb should access files from the same Berkeley DB library version.

fatal: open database /etc/aliases.db

• Consider that we have the following error on the new postfix mail server install:

  freebsd postfix/local[654]: fatal: open database /etc/aliases.db: No such file or directory

  The issue occurs as the postfix cannot locate “/etc/aliases.db.” In this case, we can resolve the error by creating the aliases.db file again.

  # postfix stop
# rm -f /etc/aliases.db
# newaliases
# postfix start

  The postfix will work open db /etc/aliases.db error free after this step.
• Check to see whether we’re mixing up two types of aliasing. We may use this at various phases of delivery while setting up the /etc/aliases.

  We only need to create an empty /etc/aliases file and then fill the /etc/aliases.db file with the postalias:

  postalias /etc/aliases 

  This solves the error.
• We can also remove the open database /etc/aliases.db error by following the command line given below. The command line will create the missing aliases.db:

  cd /etc
sudo postmap aliases 

  We must provide it with the necessary permissions. Both /etc/aliases and /etc/aliases are valid. The db should have 644 permissions root:root must own them.

  After solving the error with the method above, we should be able to restart Postfix.
• We can also remove the open database /etc/aliases.db error by renaming the file /etc/aliases to any other name. Deleting it might also remove the error. After that run the command line given below;

  sudo apt-get -f install

  A prior install of Exmim 4 may also result in the error shown above. Installing sendmail on the system may result in the creation of /etc/aliases. This includes permissions that Postfix was unable to handle. Delete the file, so Postfix can rebuild its own permissions.
• Finally, we can try commenting out the line that deleted: /etc/aliases.db in /var/lib/dpkg/info/postfix.postinst and then running 'dpkg —configure postfix'. This will solve the error and get the postfix working again.

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Conclusion

To sum up we have now gone through the postfix error open database /etc/aliases.db. We have also seen the steps to avoid the error. With the support of our Server management support services, we can remove the error easily.