6

I'm looking to map my /home folder to a different location/drive on the machine. When I view the fstab file I see the following: 

/dev/mapper/cl-home     /home            xfs     defaults        0 0
/dev/mapper/cl-swap     swap            swap    defaults        0 0
/dev/sda1   /mnt/store/hd2      ntfs    defaults,auto   0   0

My question is: what is the cl in /dev/mapper/cl-home referring to ?

Am I ok to enter it like this:

/mnt/store/hd2/home/   /home        ntfs     defaults        0 0
Gilles 'SO- stop being evil'
  • 829,060
Joe White
  • 63
  • 1
    fstab does not copy data, it only controls which volumes are mounted by the system. If you want to change the drive your home directory, copy the data to it, then change your fstab to match. What you are trying to do in the 2nd example is mount a directory on a directory, which won't work. – vespid May 06 '17 at 20:03
  • In regards to your question about what "cl" is, I'm guessing it's a volume group and the system is using LVM. To confirm, what are the outputs of these commands run as root or with sudo? pvs, vgs, lvs – TopHat May 06 '17 at 20:30

1 Answers1

6

In /etc/fstab, the first column is a volume location and the second column is a directory. The directory is the mount point, i.e. where the files will be accessible. The volume location indicates where the files are stored; there are different types of locations depending on the filesystem type. For a “normal” filesystems, the files that are stored on a disk and the volume location is a disk partition. For a network filesystem such as nfs or cifs, this indicates a host name and an exported path on the host, and so on.

What you currently have, /dev/mapper/cl-home, designates a partition using Linux's volume format (LVM). The volume name is in two parts: cl is a volume group (which covers a section of one or more disks), and home is a logical volume inside this volume group. The system doesn't care that the logical volume home and the directory /home have the same name, but it's convenient for humans to use the same name.

If you want to put your home directory on an existing Windows partition, then you can't just change the volume name here: /home would not be the place where a disk filesystem is mounted. There are several ways you can do this:

  • You can use a bind mount to make /mnt/store/hd2/home also accessible through /home. The fstab entries would be

    /dev/sda1  /mnt/store/hd2  ntfs
/mnt/store/hd2/home  /home  bind

    Note that you are not mounting an NTFS filesystem on /home: it's already mounted on /mnt/store/hd2. You're making a directory tree available at another location; the fact that this other directory tree is entirely located on an NTFS partition is not relevant.

  • You can make /home a symbolic link to /mnt/store/hd2/home. In this case /home would not appear in /etc/fstab at all.

  • You can use either a bind mount or a symbolic link for your home directory, and leave the other directories alone.

  • You can change your home directory to be /mnt/store/hd2/home. Either use a GUI to manage use accounts, or use a command like

    sudo usermod --home /mnt/store/hd2/linux-home --move-home joe

I don't recommend any of these options, because NTFS can't store all the Linux file names, types and attributes. All of these options have further gotchas:

  • Bind mounts are a very useful tool, but they do have downsides. Files are listed at all the locations in enumerations, which has consequences on locate, etc, etc.
  • A symbolic link doesn't have these downsides, but occasionally some software will record the location of your home directory with the symbolic links expanded. Having a symbolic link for /home can also cause problems due to AppArmor policies.
  • Even having a home directory outside /home can cause gotchas with security policies, though it should be ok with any major distribution nowadays.

Rather than put your home directory on an NTFS filesystem, I recommend keeping it on a Linux filesystem. To access your Windows files from Linux, access them under /mnt/store/hd2. Create symbolic links in your home directory to places under /mnt/store/hd2 for convenience.

Gilles 'SO- stop being evil'
  • 829,060
  • Thank you @Gilles for this detailed and thorough explanation. This is exactly the kind of information I was looking for. – Joe White May 07 '17 at 02:55