Today I learned as a result of reading NeddySeagoon’s reply on this thread on the Gentoo forums, that /etc/mtab is /proc/mounts.

If you chroot into a new stage tarball and run the df command there will be an error until either:

  1. /proc/mounts are copied to /etc/mtab or
  2. /proc/mounts are symlinked to /etc/mtab

The latter option is the better option since, as long as proc updates, it will keep the mtab file dynamic.

I also learned:

If you install grub manually - not using grub install, then /etc/mtab is not consulted. The manual install is documented in the handbook

I will start posting more ‘Today I learned’ entires, as they should be a helpful aid for me for look back on in the future.