I have a system with Proxmox VE 5.1 and a LXC container with Fedora 27.

The container has 2 disk (raw format), the rootfs and an additional mount point, both of them are in ext4, I want to format to xfs the second mount point.

I've tried to use the typical mkfs.xfs but I don't know where the linux block device is stored, It isn't in /dev directory.

The mount command shows:

/var/lib/vz/images/111/vm-111-disk-1.raw on / type ext4 (rw,relatime,data=ordered)
/var/lib/vz/images/111/vm-111-disk-2.raw on /var/db_data type ext4 (rw,relatime,data=ordered)

The df -h shows:

/dev/loop6       20G  1.1G   18G   6% /
/dev/loop7      9.8G   37M  9.3G   1% /var/db_data

However the "loopX" devices doesn't exist in container disk.

I've searched in proxmox forums without luck, so I don't know if this is a proxmox limitation...


In your example, the block device is /dev/loop7; It's a loop device backed by the file /var/lib/vz/images/111/vm-111-disk-2.raw. Per Wikipedia:

In Unix-like operating systems, a loop device, vnd (vnode disk), or lofi (loop file interface) is a pseudo-device that makes a file accessible as a block device.

There's no indication that your disk images contain partitions, so you can either create the filesystem from:

  1. Within the container (recommended): mkfs.xfs /dev/loop7
  2. From the host while the container is NOT running: mkfs.xfs /var/lib/vz/images/111/vm-111-disk-2.raw
  • The first option doesn't work, but the second one is Ok, thx. – Roberto Apr 16 '18 at 6:43
  • The loop device is only accessible from the host, not within the container. – Roberto Apr 16 '18 at 6:55

To access the new drive on the client use "apt install xfs" (if you are using a Debian.)

  • The OP has already shown that he can already run mkfs.xfs on the host so it's not a case of missing necessary software. – Anthony Geoghegan Apr 18 '18 at 14:35
  • Incorrect. In general LXC clients can not use host Apps. Only kernel. – SamTzu Apr 19 '18 at 10:50

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