(Resolved) Open /etc/postfix/main.cf: Permission denied

Recently, I encountered an issue on one of my mail servers where the Postfix mail system failed to send email. The error message indicated that there was a permission issue with the /etc/postfix/main.cf file. After some investigation, I was able to resolve the problem. Below, I have documented the steps I took to fix this issue, which may help others facing a similar problem.

Error: open /etc/postfix/main.cf: Permission denied

I have found the following error in log files:

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Jun 27 12:51:02 tecadmin postfix/postfix-script[11764]: starting the Postfix mail system
Jun 27 12:51:02 tecadmin postfix/master[11766]: daemon started -- version 2.10.1, configuration /etc/postfix
Jun 27 12:51:20 tecadmin postfix/sendmail[11798]: fatal: open /etc/postfix/main.cf: Permission denied

This error indicates that Postfix is unable to open the main configuration file due to insufficient permissions.

Possible Solutions

Here is possible causes and solutions for the above error:

1. Permissions

To resolve this issue, you need to ensure the correct ownership and permissions for the /etc/postfix/main.cf file. Execute the following commands in your terminal:

1. Change the owner to root:

chown root:root /etc/postfix/main.cf

2. Set the permissions to 644, allowing read and write access for the owner, and read-only access for others:

chmod 644 /etc/postfix/main.cf

3. Ensure the directory has the correct permissions:

chmod 755 /etc/postfix

2. SELinux

If SELinux is enabled on your system, it might also be causing permission issues. You can fix this by updating the SELinux context for the main.cf file and adjusting the boolean setting for HTTPD to send mail:

1. Restore the SELinux context for main.cf:

restorecon -v /etc/postfix/main.cf

2. Allow HTTPD to send mail:

setsebool -P httpd_can_sendmail=1

Additional Solutions

If the above steps do not resolve the issue, you can try the following options:

1. Check File System Errors: Sometimes, file system errors can cause permission issues. Run the following command to check and repair file system errors:

fsck -y /dev/sda1

2. Disable SELinux Temporarily: If you suspect that SELinux is causing the issue, you can temporarily disable it to see if the problem is resolved. Remember to re-enable SELinux after troubleshooting:

setenforce 0

3. Check Postfix Configuration: Verify that there are no syntax errors in the /etc/postfix/main.cf file. Use the following command to check the configuration:

postfix check

4. Restart Postfix Service: After making any changes, restart the Postfix service to apply the new settings:

systemctl restart postfix

By following these steps and additional solutions, you should be able to resolve the permission denied error when Postfix attempts to open /etc/postfix/main.cf. Ensure you have root privileges to execute these commands successfully.