The /dev/null file has become a regular file

Symptoms

Outgoing email is failing with an error similar to the following.

CONFIG_TEXT: 2025-12-09 14:07:01 1vT2Ax-0000000AfWK-2pCr failed to expand condition "${perl{discover_sender_information}}" for discover_sender_information router: Undefined subroutine &main::discover_sender_information called at /dev/null line 56.

Restarting the DNS service returns an error similar to the following:

CONFIG_TEXT: Dec 09 17:18:45 server13.servhost.com.br systemd[1]: /dev/null is not a device.

Cause

The issue occurs when /dev/null/ is a regular file instead of a character special file.

# stat /dev/null
File: /dev/null
Size: 6629 Blocks: 16 IO Block: 4096 regular file
Device: 6h/6d Inode: 29730384 Links: 1
Access: (0666/-rw-rw-rw-) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2026-06-19 14:27:14.728415900 +0000
Modify: 2026-06-19 14:30:53.647543371 +0000
Change: 2026-06-19 14:30:53.647543371 +0000
Birth: -

We've opened an internal case for our development team to investigate this further. For reference, the case number is CPANEL-50629. Follow this article to receive an email notification when a solution is published in the product.

Resolution

1. Log in to the server via SSH or WHM's Terminal as the root user

2. Move aside the regular file:

   # mv -v /dev/null{,.$(date +%s)}

3. Create the file as a character special file:

   # mknod -m 666 /dev/null c 1 3

4. Ensure that it is owned by root:

   # chown root. /dev/null