Resize container on Debian Stretch

I have lxd 3.9 on Debian Stretch (9.7). Yesterday I created a new container, and configured it. The one mistake I made is that the container is only 100 GB. I’d like to increase that to 700 GB. If I understand how this works correctly, there’s a single image, in my case it’s in:


The size of that file was 100 GB. I was able to resize it to 700 GB using:

sudo truncate -s +600G /var/snap/lxd/common/lxd/disks/default.img

But still, inside the container, I seem to be limited to 100GB (94 GB actually):

$ df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/loop2       94G   18G   75G  19% /
none            492K     0  492K   0% /dev
udev            7.8G     0  7.8G   0% /dev/tty
tmpfs           100K     0  100K   0% /dev/lxd
tmpfs           100K     0  100K   0% /dev/.lxd-mounts
tmpfs           7.9G  8.0K  7.9G   1% /dev/shm
tmpfs           7.9G  272K  7.9G   1% /run
tmpfs           5.0M     0  5.0M   0% /run/lock
tmpfs           7.9G     0  7.9G   0% /sys/fs/cgroup
tmpfs           1.6G     0  1.6G   0% /run/user/1001

I have tried to resize this container in many ways, including:

sudo btrfs filesystem resize max /var/snap/lxd/common/lxd/storage-pools/default/

which is a valid directory, but I get the error:

ERROR: not a btrfs filesystem: /var/snap/lxd/common/lxd/storage-pools/default/

Then from this post I tried to use this to resize:

nsenter -t $(pgrep daemon.start) -m – btrfs filesystem resize max /var/snap/lxd/common/lxd/storage-pools/default

as root, but I get the error: nsenter: failed to execute –: No such file or directory

My device is loop6. I know that from:

$ sudo btrfs filesystem show
Label: 'default'  uuid: ...
        Total devices 1 FS bytes used 16.82GiB
        devid    1 size 93.13GiB used 23.02GiB path /dev/loop2

But honestly I don’t understand how resizing this will help (as the guy did in the link). He used trancate, which I’m not sure is the right thing to do.

How can I resize the file system of my container to the maximum capacity of the image?

The nsenter call looks correct except for what looks like a small issue due to funny unicode characters on blog posts.

Rather than you want -- so that it looks like:

nsenter -t $(pgrep daemon.start) -m -- /snap/lxd/current/bin/btrfs filesystem resize max /var/snap/lxd/common/lxd/storage-pools/default

Note that we’ve had report of this sometimes requiring a reboot following the truncate call so that the loop device backing btrfs is properly resized.

@stgraber Thank you very much. That fixed the issue.