SUSE Linux Enterprise Server 11
Some methods of login to a SUSE Linux server are resulting in a "permission denied" error, resulting in failed login.
SIDE NOTE: Many conditions can cause a permission denied error during login. Some will prevent login; others will not. This document does not attempt to describe all possible causes, it only covers one specific scenario.
This login failure can be caused by corruption in /var/log/btmp. That file stores information about failed login attempts. A change to pam which will allow logins to succeed even if the btmp file is corrupt is available in:
SLES 11 SP4, pam-1.1.5-0.17.2, available in maintenance updates as of late June 2016.
An alternative way to resolve this is to rename or remove /var/log/btmp. The system will create a new (intact) copy when needed. Not all types of failed logins will necessarily create/update this file.
The actual conditions that must come together for corrupt /var/log/btmp to cause failed logins are relatively rare. See the "Cause" section of this document for more details.
It is not known what caused /var/log/btmp to become corrupt. Even with corruption, it might not cause a login failure in most situations. The conditions that all come together to cause actual login failures are:
1. Corruption in /var/log/btmp
2. The login attempt is controlled by a /etc/pam.d/<service> definition file, in which:
a. pam_lastlog.so is in use
b. pam_lastlog.so is set as "required" or "requisite" (it is normally considered "optional")
c. the "showfailed" option is in use on pam_lastlog.so
NOTE: Some application services announce previous login information without learning it through pam, so it is also conceivable that a corrupt /var/log/btmp could cause failures without the above pam conditions.
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