Couldn't open /dev/null Error (Linux)

From ben.goodacre.name/tech

Symptom

1. When using any command or application (such as ssh or scp) that writes to /dev/null the following error could occur:

Couldn't open /dev/null

2. When attempting to ssh the following error is given, even when SSHing to localhost:

Host key verification failed.

When running ssh -vvv user@localhost the exact debug line relating to this issue is: debug1: read_passphrase: can't open /dev/tty: Permission denied.

Cause

The permissions for the /dev/null device/special file do not allow writing to it.

Resolution

Alter the permissions using chmod, as root:

chmod a+rw /dev/tty