Helping When a User Cannot Log In

When a user has trouble logging in on the system, the source may be a user error or a problem with the system software or hardware. The following steps can help determine where the problem is:

• Check the log files in /var/log. The /var/log/messages file accumulates
system errors, messages from daemon processes, and other important
information. It may indicate the cause or more symptoms of a problem.
Also, check the system console. Occasionally messages about system
problems that are not written to /var/log/messages (for instance, a full
disk) are displayed on the system console.

• Determine whether only that one user or only that one user’s terminal/
workstation has a problem or whether the problem is more widespread.

• Check that the user’s Caps Lock key is not on.

• Make sure the user’s home directory exists and corresponds to that user’s
entry in the /etc/passwd file. Verify that the user owns her home directory
and startup files and that they are readable (and, in the case of the home
directory, executable). Confirm that the entry for the user’s login shell in
the /etc/passwd file is accurate and the shell exists as specified.

• Change the user’s password if there is a chance that he has forgotten the
correct password.

• Check the user’s startup files (.profile, .login, .bashrc, and so on). The user
may have edited one of these files and introduced a syntax error that pre-
vents login.

• Check the terminal or monitor data cable from where it plugs into the ter-
minal to where it plugs into the computer (or as far as you can follow it).
Try turning the terminal or monitor off and then turning it back on.

• When the problem appears to be widespread, check whether you can log in
from the system console. Make sure the system is not in recovery mode. If
you cannot log in, the system may have crashed; reboot it and perform any
necessary recovery steps (the system usually does quite a bit automatically).

• If the user is logging in over a network connection, run the appropriate init
script (page 507) to restart the service the user is trying to use (e.g., ssh).

• Use df to check for full filesystems. If the /tmp filesystem or the user’s
home directory is full, login sometimes fails in unexpected ways. In some
cases you may be able to log in to a textual environment but not a graphi-
cal one. When applications that start when the user logs in cannot create
temporary files or cannot update files in the user’s home directory, the
login process itself may terminate.