[SOLVED] move /usr to /home/usr

WFV · 06-18-2017, 04:11 PM

Have read several websites on doing this but getting stuck at reboot "can't find sbin/init, you're on your own" to a # prompt. I'm guessing that /usr isn't binding in time for the kernel to finish booting up?
1. boot guest with live cd (in this case its an iso in a VirtualBox guest on a Linux host)

Code:

 lsblk
mkdir /mnt/ARCH
mount /dev/sda1 /mnt/ARCH
mount /dev/sda3 /mnt/ARCH/home
cd /mnt/ARCH
mount -t proc proc proc/
mount -o bind /sys sys/
mount -o bind /dev dev/
cd /
chroot /mnt/ARCH
nano /etc/fstab
# Binds (under the /home mount)
/home/var /var none bind 0 0
/home/usr /usr none bind 0 0
#save + exit
rsync -aAXhv /var /home/
rysnc -aAXhv /usr /home/
exit (chroot)
rm -rfv /mnt/ARCH/var/*
rm -rfv /mnt/ARCH/usr/*
mount -o bind /mnt/ARCH/home/var /mnt/ARCH/var
mount -o bind /mnt/ARCH/home/usr /mnt/ARCH/usr
chroot /mnt/ARCH
# check to see that all is intact in /var and /usr
# check to see that commands work (the above line will do that)
exit (chroot)
umount -l -a
reboot

fails to boot on "can't find sbin/init" however, from the prompt /sbin contains init. So I'm guessing the failure is due to the symlinks in sbin to /usr/bin are needed and the bind /usr hasn't completed yet?
This one in particular can't initiate systemd?
Should the bind in fstab be passed with -f?
Thanks anyone.

Didier Spaier · 06-18-2017, 04:22 PM

I know neither Arch nor systemd but this message can be displayed if the partition mounted as / is not the good one, i.e. is not the root partition of the system you want to boot.

rknichols · 06-18-2017, 04:38 PM

Heed the warning from the Arch Linux Partitioning Guide:

Warning: Directories essential for booting (except for /boot) must be on the same partition as / or mounted in early userspace by the initramfs. These essential directories are: /etc and /usr [1]

and the linked-to warning from freedesktop.org: "Booting Without /usr is Broken".

If you insist on a separate /usr partition, you must make provision in the initramfs to mount it in the early stages of the boot process. That may require that you disable any automatic fsck of your /usr partition lest it always fail because the partition is mounted.

WFV · 06-18-2017, 05:03 PM

Thank you rknichols, that link sums it up. maybe i try the initramfs tweaks, but probably over my head. Its just a vbox guest and have a good backup to replace it with

EDIT: I'm going to mark this solved as I went back and only moved /var (needed a little extra room in / of the vbox guest and didn't want to grow the vdi). Shutdown fails to unmount the var bind, but the guest boots up normal and everything works. Thanks for the replies all.

rknichols · 06-19-2017, 10:56 AM

Quote:

Originally Posted by WFV

maybe i try the initramfs tweaks, but probably over my head.

It might not be difficult, but for what you are doing you would also have to mount /home early. In Red Hat 6, all I would need to do is to create a file /etc/fstab-sys with two lines like:

Code:

/dev/sda3   /home ext4  defaults     0 0
/home/usr   /usr  none  bind         0 0

and change the "/usr" and "/home" lines in /etc/fstab to have "0" in the last field so that the init scripts wouldn't try to run an fsck on those mounted filesystems. Then, a run of mkinitrd would include that /etc/fstab-sys in the initramfs. I had one system set up in a similar way (separate /usr, not part of any other filesystem, mounted read-only), but got tired of having to remember to remount /usr read/write every time I did an update.

Since my /usr was getting mounted read-only, I wasn't too concerned about turning off the boot fsck. For your case, I don't think doing that for /home is a good idea, so the whole plan falls apart on that note.