SELinux is enabled by default on some Linux distributions including Oracle Linux, RHEL, CentOS, and Fedora. Use the sestatus command to determine if SELinux is enabled on your distribution:

$> sestatus
SELinux status:                 enabled
SELinuxfs mount:                /sys/fs/selinux
SELinux root directory:         /etc/selinux
Loaded policy name:             targeted
Current mode:                   enforcing
Mode from config file:          enforcing
Policy MLS status:              enabled
Policy deny_unknown status:     allowed
Memory protection checking:     actual (secure)
Max kernel policy version:      31

If SELinux is disabled or the sestatus command is not found, refer to your distribution's SELinux documentation for guidance before enabling SELinux.