In CentOS 7.3, permissions of the /var/log/wtmp file is handled by /lib/tmpfiles.d/var.conf, which is executed after every reboot. To change default permissions, change permissions in the following script.
# cat /lib/tmpfiles.d/var.conf | grep wtmp f /var/log/wtmp 0664 root utmp -
In CentOS 7.0, 7.1, and 7.2, permissions for /var/log/wtmp is managed by file /lib/tmpfiles.d/systemd.conf, which is executed after every reboot. To change default permissions, change permissions in the following script.
# cat /lib/tmpfiles.d/systemd.conf | grep wtmp f /var/log/wtmp 0664 root utmp -
Regardless of the CentOS version, if a custom file named /etc/tmpfiles.d/var.conf is generated in the /etc/tmpfiles.d/ directory, it will take precedence over a similar file in /lib/tmpfiles.d/.
