I’m working on a fun little project to set up a custom-made bootable usb key. But I ran into a little trouble after using a chroot, due to /dev and mount --rbind.
# mount -t proc none /mnt/gentoo/proc # mount --rbind /sys /mnt/gentoo/sys # mount --rbind /dev /mnt/gentoo/dev # mount -t tmpfs tmpfs /mnt/gentoo/tmp # mount -t tmpfs tmpfs /mnt/gentoo/var/tmp # mount -t tmpfs tmpfs /mnt/gentoo/usr/src # mount | grep gentoo /dev/sde1 on /mnt/gentoo type ext2 (rw) none on /mnt/gentoo/proc type proc (rw) /sys on /mnt/gentoo/sys type none (rw,bind,rbind) /dev on /mnt/gentoo/dev type none (rw,bind,rbind) tmpfs on /mnt/gentoo/tmp type tmpfs (rw) tmpfs on /mnt/gentoo/var/tmp type tmpfs (rw) tmpfs on /mnt/gentoo/usr/src type tmpfs (rw) # chroot /mnt/gentoo
All’s well, until it’s time to exit the chroot and unmount everything..
# umount /mnt/gentoo/usr/src /mnt/gentoo/var/tmp \
/mnt/gentoo/tmp /mnt/gentoo/sys /mnt/gentoo/proc \
/mnt/gentoo/dev /mnt/gentoo
umount: /mnt/gentoo/dev: device is busy.
(In some cases useful info about processes that use
the device is found by lsof(8) or fuser(1))I don’t see anything mounted under there. Fuuuu…
# mount | grep gentoo /dev/sde1 on /mnt/gentoo type ext2 (rw) # lsof|grep gentoo # fuser -m /mnt/gentoo /mnt/gentoo: #
Rebooting at this stage is inconvenient, but will certainly solve the problem. But what is left using /mnt/gentoo/dev?
Googling around, and seeing some people with similar problems, finally lit a light bulb above my head:
# cat /proc/mounts | awk '{print $2}' | grep gentoo
/mnt/gentoo
/mnt/gentoo/dev
/mnt/gentoo/dev/pts
/mnt/gentoo/dev/shmSo mount --rbind worked as advertised and recursively mounted /dev and everything sub-mounted. And I didn’t realize that udev mounted other things under /dev without updating /etc/mtab. Sigh.
# umount /mnt/gentoo/dev/shm /mnt/gentoo/dev/pts /mnt/gentoo/dev /mnt/gentoo #
And now I can get on with my life.
