e2fsck supports -C <fd> to output progress data to an auxillary
However, /sbin/fsck doesn't properly handle this option.
/sbin/fsck -C4 /dev/sda1
gets translated to:
e2fsck -4 -C0 /dev/sda1
e2fsck -C4 -f /tmp/boot.img 4> test
Has written completion information to test.
It works in e2fsck, but you can't pass it to /sbin/fsck and get it
passed right. i.e., /sbin/fsck -C4 -f /tmp/boot.img wouldn't work.
Fixed in rawhide in rpm e2fsprogs-1.35-11 or newer.