Where and when /etc/fstab is checking during boot

[Gary Jennejohn]

On Sun, 4 Mar 2012 19:32:36 -0500
Robert Simmons <rsimmons0 at gmail.com> wrote:

> I've just finished working though building a FreeBSD box with an
> encrypted root partition as mentioned in the geli(8) man page: "Ask
> for the passphrase on boot, before the root partition is mounted.
> This makes it possible to use an encrypted root partition.  One will
> still need bootable unencrypted storage with a /boot/ directory, which
> can be a CD-ROM disc or USB pen-drive, that can be removed after
> boot."
> 
> I've noticed something quite interesting about the way that fstab is
> read during boot.  If you follow the instructions exactly as they are
> written in the geli(8) man page you soon discover that you also must
> have an /etc/fstab file in that same unencrypted partition.  But this
> need not be the complete fstab file.  It only needs to have the one
> line that describes /.
> 
> Later, after the encrypted partition is mounted, the /etc/fstab inside
> the encrypted partition is then read and all other partitions listed
> in fstab are mounted as written there.
> 
> I've tested this by putting empty fstabs and fstabs with just the line
> for / in both locations and booting to see what happens.
> 
> Is this the correct behavior?  Shouldn't the fstab file be read
> completely once and not twice?
>

man 5 fstab

It isn't explicitly stated, but implied, that fsck(8), mount(8) and
umount(8) parse fstab every time they're invoked.

It's a feature.

-- 
Gary Jennejohn