systemd-remount-fs.service, systemd-remount-fs - Remount root and kernel file
systemd-remount-fs.service is an early boot service that applies mount options
listed in fstab(5), or gathered from the partition table (when
systemd-gpt-auto-generator(8) is active) to the root file system, the
/usr file system, and the kernel API file systems. This is required so that
the mount options of these file systems — which are pre-mounted by the
kernel, the initial RAM disk, container environments or system manager code
— are updated to those configured in /etc/fstab and the other sources.
This service ignores normal file systems and only changes the root file system
(i.e. /), /usr, and the virtual kernel API file systems such as /proc, /sys or
/dev. This service executes no operation if no configuration is found
(/etc/fstab does not exist or lists no entries for the mentioned file systems,
or the partition table does not contain relevant entries).
For a longer discussion of kernel API file systems see API File
Note: systemd-remount-fs.service is usually pulled in by
systemd-fstab-generator(8), hence it is also affected by the kernel
command line option fstab=, which may be used to disable the
generator. It may also pulled in by systemd-gpt-auto-generator(8),
which is affected by systemd.gpt_auto and other options.