Is it possible to move /home mount point from one disk to the disk where / mount point is?

Question

I have this setup of Ubuntu 18: two identical disks. In one (sda) there is / and /boot/efi. In the other disk (sdb) there is /home.

The free space in sda is enough to hold what is used in sdb.

I would like to move /home to sda. It could be the same partition sda1, or it could be a new partition, say sda3.

Here is what gparted shows me:

Is it possible to make this moving?

I don't know if what I'm saying makes sense, but my plan is:

• resize sda1 to say, 200GB
• format the empty space in sda to ext4 (creating sda3)
• copy the content of sdb1 to sda3
• tell linux that /home now is in sda3 (this part I have no idea how to do)

Answer 1

If you use sudo or su instead of logging in directly, you will still lock the home directory and you will be unable to umount /home. If you cannot login directly, you should probably use a live CD.

Another option however would be:

• create a user safemove, with a home directory /tmp.
• add safemove to the sudoers file with visudo
• log in with safemove at the terminal (typically control-shift-f1). This will prevent the creation of the complete graphical desktop under /tmp.
• make sure everybody else is logged off.
• as safemove, sudo -s
• mkdir /mnt/home
• umount /home
• mount /dev/sdb1 /mnt/home
• copy /mnt/home/* to /home if you do not want a separate partition, including ownership and permission flags.
• remove /home from /etc/fstab
• take a deep breath and reboot.

You should now have everything in /dev/sda1. Check this first before removing the user safemove.

If you are going to mess with /home, it is always good to have, at least temporarily, a userid that does not have its homedir under /home and that can sudo and/or su.

If you want to

Answer 2

It is possible, but you should login as root in order to avoid locking /home. Then you can unmount /home, remount it elsewhere (let’s suppose /mnt), then copy all files from /mnt to /home preserving the permissions (cp -rp /mnt/* /home). Then edit /etc/fstab and change where you mount sdb1.

If you can’t login as root, use a Live CD.

However, having a separate /home enables you to reformat / if you want to change the OS keeping your personal file. But surely, nearly 1TB for the OS is quite important.

Answer 3

YES

my /etc/fstab for example is

UUID=800e924a-a869-4152-9503-9d9cfecbd16e                /                       xfs     defaults        0 0
UUID=4f3da85a-71a9-4f6e-bc5f-dfd23a880b08                /boot                   xfs     defaults        0 0
UUID=1FAB-9515                                           /boot/efi               vfat    umask=0077,shortname=winnt 0 0
/dev/disk/by-uuid/e0791b9e-b620-4274-9857-78389b10f5a5   /data auto nosuid,nodev,nofail,x-gvfs-show 0 0

# my /data is a 15tb hardware raid-5, comes in as /dev/sda1
# my root partition comes in as /dev/sdb3, with /boot and /boot/efi as sda2 and sda1.

I do not have /home as mounted as a separate partition. If it was you would see it as an entry in /etc/fstab as such, it will be quite obvious.

In your case you want to make /home on your root partition, so here is what I would do

• your existing home is mounted as a separate partition, reference it from /etc/fstab
• mkdir /newhome
• cp -rp /home/* /newhome/
• umount /home
• rmdir /home
• mv /newhome /home
• remove the mount point of /home from your /etc/fstab; that's all that really needs to happen if you want to have /home on your root / partition {which is already being mounted in /etc/fstab as /)

note: the umount command will likely result in failure if logged in as a user where that mount will inherently be busy. So if you log in as root, whose home directory is /root and not under the mounted /home you should have no problem.

note2: you don't even need to use the /home folder convention, simply change the location of user folders in /etc/passwd to wherever you want those user account home folders to reside. For example all my user accounts on my server specified in /etc/passwd have home folders under /data/users/<name>. I do have a /home folder present, but it has nothing in it. My /data is mounted in /etc/fstab and is a raid-5 bunch of disks making 10 tb worth of space.