pam_tally2 comes in two parts: pam_tally2.so and pam_tally2. The former is the PAM module and the latter, a stand-alone program. pam_tally2 is an (optional) application which can be used to interrogate and manipulate the counter file. It can display users' counts, set individual counts, or clear all counts. Setting artificially high counts may be useful for blocking users without changing their passwords. For example, one might find it useful to clear all counts every midnight from a cron job.
Normally, failed attempts to access root will not cause the root account to become blocked, to prevent denial-of-service: if your users aren't given shell accounts and root may only login via su or at the machine console (not telnet/rsh, etc), this is safe.
The auth and account module types are provided.
pam_tally2 is not compatible with the old pam_tally faillog file format. This is caused by requirement of compatibility of the tallylog file format between 32bit and 64bit architectures on multiarch systems.
There is no setuid wrapper for access to the data file such as when the pam_tally2.so module is called from xscreensaver. As this would make it impossible to share PAM configuration with such services the following workaround is used: If the data file cannot be opened because of insufficient permissions (EACCES) the module returns PAM_IGNORE.
Add the following line to /etc/pam.d/login to lock the account after 4 failed logins. Root account will be locked as well. The accounts will be automatically unlocked after 20 minutes. The module does not have to be called in the account phase because the login calls pam_setcred(3) correctly.
auth required pam_securetty.so auth required pam_tally2.so deny=4 even_deny_root unlock_time=1200 auth required pam_env.so auth required pam_unix.so auth required pam_nologin.so account required pam_unix.so password required pam_unix.so session required pam_limits.so session required pam_unix.so session required pam_lastlog.so nowtmp session optional pam_mail.so standard
pam.conf(5), pam.d(5), pam(8)
pam_tally2 was written by Tim Baverstock and Tomas Mraz.