“Reformat the filesystem to enable support”

Apparently it’s been a while since I ran containers on my office computer—and by a while, I mean, since November 2016—because if your initial install was RHEL or CentOS 7.2 or older then neither Docker nor Podman will work:

# yum -q -y install podman skopeo buildah
# podman pull registry.access.redhat.com/ubi7/ubi
Error: could not get runtime: kernel does not support overlay fs: overlay: the backing xfs filesystem is formatted without d_type support, which leads to incorrect behavior. Reformat the filesystem with ftype=1 to enable d_type support. Running without d_type is not supported.: driver not supported

So… ugh. I didn’t have any disks it’d work on either:

# for i in $(awk '{ if ($3 == "xfs") print $2 }' /etc/mtab); do xfs_info $i; done | grep ftype
naming   =version 2              bsize=4096   ascii-ci=0 ftype=0
naming   =version 2              bsize=4096   ascii-ci=0 ftype=0
naming   =version 2              bsize=4096   ascii-ci=0 ftype=0
naming   =version 2              bsize=4096   ascii-ci=0 ftype=0

I didn’t reformat anything though. podman pull wants overlayFS on /var/run/containers/storage, and buildah bud wants it on /var/lib/containers/storage. I made loopback disks for both:

1. Find/make space somewhere, then create a directory to put the images in:

   # mkdir -p /store/containers

2. Create a big file, whatever size you want, for the disk image. I made mine 20GiB. It took a couple minutes, my disks are slow:

   # dd if=/dev/zero of=/store/containers/var_lib_containers.img bs=1M count=20K

3. Find a free loop device and associate the file to it:

   # losetup -f /dev/loop1
   # losetup /dev/loop1 /store/containers/var_lib_containers.img 
   

4. Format the “device”, then detach it from the file:

   # mkfs -t xfs -n ftype=1 /dev/loop1
   # losetup -d /dev/loop1

5. Mount the “disk”, and see if it worked:

   # mount -oloop /store/containers/var_lib_containers.img /var/lib/containers
   # df -h /var/lib/containers
   Filesystem      Size  Used Avail Use% Mounted on
   /dev/loop1       20G   33M   20G   1% /var/lib/containers

6. It worked? Make it permanent:

   # echo "/store/containers/var_lib_containers.img /var/lib/containers xfs defaults,loop 1 2" >> /etc/fstab

Rinse and repeat for the other drive it needed. Then try again:

# podman pull registry.access.redhat.com/ubi7/ubi
Trying to pull registry.access.redhat.com/ubi7/ubi...Getting image
source signatures
Copying blob bff3b73cbcc4 done
Copying blob 7b1c937e0f67 done
Copying config 6fecccc91c done
Writing manifest to image destination
Storing signatures
6fecccc91c83e11ae4fede6793e9410841221d4779520c2b9e9fb7f7b3830264