Exclude specific users from pam_slurm restriction

exclude_specific_users_from_pam_slurm.rst

CAUTION: Please test this on a test machine/VM before you actually do this on your slurm compute node.

Step 1. Make sure pam_listfile.so exists on your system. The following command is an example on Redhat 6:

ls -la /lib64/security/pam_listfile.so

Step 2. Create user list (e.g. /etc/ssh/allowed_users):

# /etc/ssh/allowed_users
root
myadmin

And, change file mode to keep it secret from regular users(Optional):

chmod 600 /etc/ssh/allowed_users

NOTE: root is not necessarily listed on the allowed_users, but I feel somewhat safe if it's on the list.

Step 3. On /etc/pam.d/sshd, add pam_listfile.so with sufficient flag before pam_slurm.so (e.g. my /etc/pam.d/sshd looks like this):

#%PAM-1.0
auth       required     pam_sepermit.so
auth       include      password-auth
account    sufficient   pam_listfile.so item=user sense=allow file=/etc/ssh/allowed_users onerr=fail
account    required     pam_slurm.so
account    required     pam_nologin.so
account    include      password-auth
password   include      password-auth
# pam_selinux.so close should be the first session rule
session    required     pam_selinux.so close
session    required     pam_loginuid.so
# pam_selinux.so open should only be followed by sessions to be executed in the user context
session    required     pam_selinux.so open env_params
session    optional     pam_keyinit.so force revoke
session    include      password-auth

Done. Now your allowed users should be able to login to the compute node.