Controls-docs/admin-guide/troubleshooting/login.md

Login and Remote Access

When a user cannot log in on a system, it is usually caused by one of these:

1. The password is wrong.
2. Access hasn't been granted through Hiera (aaa::admins and aaa::users) or /etc/security/ssh.allow.*. The latter also has to be enabled in Hiera.
3. Log in as root is attempted from a system that is not a bastion host (eg wmgt0*.psi.ch or *-gw.psi.ch).
4. In the case of Gnome logins, the problem might be caused by the home directory being inaccessible (eg because AFS doesn't work properly).
5. sssd(8) may have problems.

Regarding #3 note that on some systems the configured bastion host is wmgt*.psi.ch even though it is not actually possible to log in from there, because the PSI firewall only allows connections from a certain gateway, eg foobar-gw.psi.ch.

Known Errors

pam_sss System Error

pam_sss(sshd:account): Access denied for user xxxxxx_y: 4 (System error)

Here the AD join might be broken. The machine can be rejoined by deleting/moving away /etc/krb5.keytab and then running Puppet (puppet agent -t).

Notes

For normal users there will be a pam_access(8) error even for successful logins. The reason is that we use pam_access twice. First for admins and then - depending on the system's configuration - for normal users. Obviously the first one will fail unless the user in question is recognized as an admin.