When I try to log in as root I get the following message
realloccg /: file system full sendmail [487]:NO Queue:low on space (have 0,SMTP-DAEMON needs 101 in /var/spool/mqueue)
What should I do?
You should review your filesystem and remove or prune logfiles and other non-essential files. You might consider moving logfiles and queues to another filesystem and set up a symbolic link to the new filesystem.
For more information on symbolic links, search the forums with the keywork "symbolic link".