Grub: file not found

[Ralf Mardorf]

On Tue, 2014-01-07 at 16:49 -0500, Jerry Lapham wrote:
> Since the file is actually there, I want to know if there is any other
> problem which which might be misreported as an "Error 15:  File not
> found."

Hi Jerry,

the file might be there, but there could be several reason that the file
isn't found.

Is this the complete error message? Is there no information about the
stage?

It might be that the entry in grub.cfg doesn't use the correct partition
and tries to boot another linux install.

Or assumed /boot is on an own partition, that /boot isn't mounted at
startup. I don't know if fstab is important (resp. not exactly at what
point fstab becomes important) or if GRUB does it completely on it's
own, however "grub-install –boot-directory=[...] /dev/sda" is the
command to fix grub.

If the start position of a boot partition changed, you anyway need to
reinstall grub, at least by "grub-install /dev/sda".

Stage 1 is in the MBR or what ever you're using.
Stage 2 already is inside the Linux install, so if the error message
contains a failure at stage 1.5, you need to reinstall grub.

chroot from another Linux install into the broken Linux install and fix
grub by "grub-install /dev/sda".

Since you're not providing enough information, it's hard to say what the
culprit is.

I'm not a grub expert and my Linux are all completely inside /,
IOW /boot isn't on it's own partition on my machine.

To get a first rough impression, please post

- the complete original error message
- /etc/fstab of the "broken" Linux, IOW from another Linux it's
  /mountpoint/etc/fstab
- ls /boot > ls.txt, resp. ls /mountpoint/boot > ls.txt
- /boot/grub/grub.cfg, resp. /mountpoint/grub/grub.cfg
- I suspect you did some Internet research on your own, what happened
  when you followed the instructions of a thread, that is marked as
  solved. What output did you get, when such a howto didn't solve the
  issue on your machine?

Another issue could be caused by using /dev/sda[...] instead of an uuid
or label for the grub.cfg entry. There is no guaranty that sda always is
sda, even while it's unlikely that sda will change when using common
hardware.

Instead of chroot to reinstall grub, it's also possible to use a Linux,
e.g. from a live CD that does use systemd instead of init scripts or
upstart and use systemd-nspawn (maybe easier to use than chroot).

Regards,
Ralf