Mounting your filesystems
One of the first things init does is mount your filesystems. The kernel will have mounted the root filesystem when it started, but it’s often mounted read-only. Mounting filesystems is controlled by the contents of /etc/fstab , which lists the devices to mount, their mount points and any options to use when mounting them. The root filesystem is remounted read-write, then the other local filesystems, including swap, are mounted. Any filesystems with the noauto option set aren’t mounted and network filesystems are left until the network is available. While this task was traditionally handled by init , things have changed recently. It can no longer be guaranteed that everything needed for early boot is on the root filesystem, particularly on systems that use a separate filesystem for /usr , so most distros now mount the local filesystems, or at least the critical ones, from the initramfs before passing control to init .