checkroot.sh: check for conflicting configurations
In our current boot scripts, two ways are used to determine whether
the rootfs is read-only or not. One by checking the READ_ONLY_ROOTFS
value in /etc/default/rcS, the other by checking the /etc/fstab entry.
>From a normal Linux user's point of view, the way of checking the
/etc/fstab entry is preferred. However, as there are several boot scripts
that need to know whether rootfs is read-only or not, checking /etc/fstab
in each script brings too much overhead. Thus, these boot scripts
use the READ_ONLY_ROOTFS value in /etc/default/rcS.
In normal use cases, there would be no problem, as both /etc/default/rcS and
the /etc/fstab are modified at rootfs time. However, if the user changes
the mount option for rootfs in /etc/fstab to read-write, and he/she forgets
to change the value in /etc/default/rcS, there would be unexpected results.
For example, the udev-cache would still be disabled.
So at a minimal, a check for conflicting configurations between /etc/fstab
and /etc/default/rcS should be added in checkroot.sh so that there would be
reasonable warnings if users have configured the system in a non-consistent
way.
[YOCTO #4880]
Signed-off-by: Chen Qi <Qi.Chen@windriver.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
