Operation Manual
• If the systemis configured to useKerberos,the system'slocal time may have
drifted past the acceptedvariance with the Kerberos servertime (this is typically
300 seconds). If NTP (networktime protocol) is not workingproperly or local
NTP serversare not working,Kerberos authenticationceases to function because
it dependson common clock synchronization across the network.
• The system'sauthenticationconfigurationis misconfigured. Check the PAM
configurationfiles involved for any typographicalerrors or misordering of direc-
tives. For additional background information about PAM and the syntaxof the
configurationfiles involved, refer to Chapter 2, Authenticationwith PAM (↑Secu-
rity Guide).
• The homepartitionis encrypted.Find more informationaboutthis topicin Section
“Login to EncryptedHome Partition Fails” (page 98).
In all casesthat do not involve external networkproblems,the solution is to reboot
the system into single-usermode and repair the configuration before booting again
into operating mode and attemptingto log in again. To boot into single-usermode:
1 Reboot the system.The boot screen appears,offeringa prompt.
2
Enter
1
at the boot prompt to make the system boot into single-usermode.
3
Entertheusernameand password for
root
.
4 Make all the necessarychanges.
5
Boot into the full multiuserand networkmodeby entering
telinit5
at the
command line.
Valid Usernameand Password Not Accepted
This is by far the most common problem users encounter,becausethere are many
reasons this can occur. Dependingon whetheryou use local user managementand
authenticationor network authentication,login failures occur for different reasons.
Local user managementcan fail for the following reasons:
• The usermay haveentered thewrong password.
• The user'shome directorycontainingthe desktopconfigurationfiles is corrupted
or write protected.
• There may be problemswith the X Window Systemauthenticatingthis particular
user, especiallyif the user'shome directory has been used with another Linux
distributionprior to installing the current one.
To locatethe reasonfor a local login failure, proceedas follows:
1 Checkwhetherthe userremembered his password correctlybefore you start
debugging the whole authenticationmechanism.If the user may not remember
Help and Troubleshooting 95