Docker uses root partition, might need more storage space

Hi guys,

First post here, sadly it’s regarding support. Docker seems to use my /root partition which is only 20 GB and the rest of my 2TB drive is on /home.

root@legio:~# df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/root        20G  8.3G  9.9G  46% /
devtmpfs        7.8G     0  7.8G   0% /dev
tmpfs           7.8G  4.0K  7.8G   1% /dev/shm
tmpfs           7.8G  394M  7.4G   5% /run
tmpfs           5.0M     0  5.0M   0% /run/lock
tmpfs           7.8G     0  7.8G   0% /sys/fs/cgroup
/dev/md2        487M   25M  433M   6% /boot
/dev/md4        1.8T   51G  1.7T   3% /home
overlay          20G  8.3G  9.9G  46% /var/lib/docker/overlay2/aa30e247cdd1f95098ce909f333aae8a968b431c07856f242614528d6e2490c3/merged
shm              64M  4.0K   64M   1% /var/lib/docker/containers/201cd5c089c15b57b38fc94b3331212494d0a9514ea6ca51ec88bbcacce0cf0a/shm
overlay          20G  8.3G  9.9G  46% /var/lib/docker/overlay2/d249b6017bcfdae9742caed4402fe02936b1ddb55eb5178504d161061d49f178/merged
shm              64M     0   64M   0% /var/lib/docker/containers/0b11fcac390be8525e451bf00270916063c7da519c368e170c49f5f741c1b425/shm

Can you let me know of any way I can make use of more space without having to resize partitions? It’s risky business while they’re mounted and data loss isn’t something anyone likes to deal with. :slight_smile:

Running Debian 9.1 stable on a dedicated machine.

Any help will be appreciated.


Do we have a #howto for this @techapj? That is, configuring Discourse to use another drive for the high storage requirement items like the database, file/image uploads, backups, etc?


That would be the easiest solution, yeah. :slight_smile:

This topic, though related to digital ocean block storage, can help you at least for uploads:

You should read all the topic, there are pros and cons.

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Creating symlinks doesn’t seem like a very good way in my opinion, it’s too workaround-y. Lets see what @codinghorror and @techAPJ will come up with.

There is no #howto for this as of now, added on my list to look into it and write one. :memo:


Thanks! The 20 gigs I have should be sufficient for now but it’ll be useful.

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I did this for free codecamp:

  - volume:
      host: /var/discourse/shared/standalone
      guest: /shared
  - volume:
      host: /var/discourse/shared/standalone/log/var-log
      guest: /var/log
  - volume:
      host: /var/postgres_data
      guest: /shared/postgres_data

Basically I keep /var/postgres_data in root and then mount /var/discourse/shared/ on the second volume, additionally I put docker containers in /var/discourse/shared/docker

There are many ways of skinning this, just keep postgres_data on the fastest drive and you should be good.


Another solution on OS level can be to mount /var/lib/docker on a dedicated partition.

To do this, please, stop Docker, make sure that no process accesses /var/lib/docker and do the following:

Provide an additional volume. In this example it is /dev/sdx8.
Format it accordingly, i.e.

mkfs.xfs -n ftype=1 /dev/sdx8


mkfs.ext4 /dev/sdx8


If it fails in mkfs.xfs you might run a newer version of mkfs.xfs which has ftype=1 already as default. Just issue

mkfs.xfs /dev/sdx8

Stop Docker.

service docker stop

Make sure the directory is not used anymore:

lsof | grep /var/lib/docker

Prepare directories and mount the new volume:

mv /var/lib/docker /var/lib/__docker
mkdir /var/lib/docker
mount /dev/sdx8 /var/lib/docker

Move all contents there to:

rsync -aH /var/lib/__docker/ /var/lib/docker
# mind the trailing slash. It takes care to copy the whole tree to the right position.

Don’t forget to add /dev/sdx8 to /etc/fstab.

Remove the old directory if everything is fine.

rm -rf /var/lib/__docker

If following the above guide, as a semi-newb, let me know if I got this right:

  1. Assume mounted volume is at /mnt/someVolume/
  2. Make an empty dir at mnt vol?
mkdir /mnt/someVolume/discourse/shared/
  1. When you say ‘mount’, do you mean symlink?
ln -s /mnt/someVolume/discourse/shared /var/discourse/shared
  1. Edit /var/discourse/containers/app.yaml
  - volume:
      host: /var/discourse/shared/standalone
      guest: /shared
  - volume:
      host: /var/discourse/shared/standalone/log/var-log
      guest: /var/log
  - volume: #KEEP THE SAME, right?
      host: /var/postgres_data
      guest: /shared/postgres_data
  1. move docker containers?
mv /var/discourse/containers /mnt/someVolume/discourse/shared/containers

Then maybe stop/start again? Do I need to rebuild? Anything missing or need correcting?

This stuff is messy, I recommend you create a test droplet and try it out there, it’s the easiest way to answer all questions with zero risk

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Does this mean my summary interpretation is also on the right track?

I’m not sure if a test droplet is the best way to go, in my case. The IPs will be different, I’d have to setup a new host, and even if I did all that, nginx would be completely off… I’m pretty sure this would be even-more confusing. I’d probably be better off just making a backup before I change anything.

About to try this on a fresh install. I’ll report back.

Okay, this is my /etc/fstab

# <file system> <mount point>   <type>  <options>       <dump>  <pass>
/dev/md3        /       ext4    errors=remount-ro,relatime      0       1
/dev/md2        /boot   ext4    errors=remount-ro,relatime      0       1
/dev/md4        /home   ext4    defaults,relatime       1       2
/dev/sda5       swap    swap    defaults        0       0
/dev/sdb5       swap    swap    defaults        0       0
proc            /proc   proc    defaults                0       0
sysfs           /sys    sysfs   defaults                0       0
tmpfs           /dev/shm        tmpfs   defaults        0       0
devpts          /dev/pts        devpts  defaults        0       0

When I do mkfs.ext4 /dev/sdx8 do I have to do it to /dev/md4? It’s my biggest partition.


Based on @sam’s suggestion I spun up a new droplet → installed Discourse → added a block storage volume → moved uploads and backups to that volume. Everything worked out fine. Here is the howto:


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