Re: "Run fsck manually"..?

[Greg Wooledge <wooledg@eeg.ccf.org>]

On Wed, Feb 03, 2021 at 10:02:42AM -0600, David Wright wrote:
> T'other way, I think, but no matter. For the record, there are
> two different "strengths" for fsck:
> 
>   fastboot|fsck.mode=skip)
>     fastboot=y
>     ;;
>   forcefsck|fsck.mode=force)
>     forcefsck=y
>     ;;
>   fsckfix|fsck.repair=yes)
>     fsckfix=y
>     ;;
>   fsck.repair=no)
>     fsckfix=n
>     ;;

Where is this coming from?

> If you have a separate /boot that is not on a filesystem needing
> fscking, then you can use the normal mechanism supported by grub¹.

> ¹ It writes to the file /boot/grub/grubenv, hence the caution.

What is the "normal mechanism"?  Where is it documented?

There are no man pages for "grub" or for "grubenv" on my system.
There is a /boot/grub/grubenv file but it consists of one comment line,
ending in a newline, and then enough # characters to make the file size
exactly 1024 bytes.  Incomprehensible.