This is a very special use case when you only need to run small and temporary containers with small disk usage and don't want to use your Array Disks (HDDs).

 

Note: The RAM-Disk, all containers, their data and docker.img are lost after reboot / power-outage. So you maybe want to add the code to your Go-File to automatically re-create the RAM-Disk on reboot. Of course the containers will be still lost. This means, this guide is only useful for containers which contain tools for temporary usage. Feel free to use a persistent appdata path, but of course the containers will be re-downloaded on every reboot.

 

In this example we use a 2GB RAM Disk (change count=2000 if you need more):

mkdir -p /mnt/disks/docker/appdata
mkdir /mnt/disks/docker/service
mount -t ramfs ramfs /mnt/disks/docker/appdata/
dd if=/dev/zero of=/mnt/disks/docker/appdata/docker.img bs=1M count=2000
mkfs.xfs /mnt/disks/docker/appdata/docker.img
mount -o loop /mnt/disks/docker/appdata/docker.img /mnt/disks/docker/service

 

Now /mnt/disks/docker/appdata/ is a RAM-Disk. In this path we created a 2GB xfs-formatted docker.img file, which is mounted on /mnt/disks/docker/service. By that we need to change the docker settings as follows:

 

After installing a "jlesage/mkvtoolnix" container, it returns the following usage:

du -hd1 /mnt/disks/docker
2.0G    /mnt/disks/docker/appdata
651M    /mnt/disks/docker/service
2.6G    /mnt/disks/docker

 

df -ah | grep /mnt/disks/docker
none               0     0     0    - /mnt/disks/docker/appdata
/dev/loop2      2.0G  386M  1.6G  20% /mnt/disks/docker/service
tmpfs           7.7G   68K  7.7G   1% /mnt/disks/docker/service/containers
overlay         2.0G  386M  1.6G  20% /mnt/disks/docker/service/overlay2/3e72cc7e467ed786983b98fbb8273ac2f922be7dd087c87811a5dadf30c0c19a/merged

 

This means we used 651MB of the 2GB docker.img. Any data which would be written to /appdata would raise the RAM usage!

 

You want to reset everything? Execute this:

umount /mnt/disks/docker/service
umount /mnt/disks/docker/appdata
rm -r /mnt/disks/docker/*

 

Would it be complicated to copy/move the docker-xfs.img to pool or array at shutdown and back again to ram at power up?

I have lots of unused ram so I have been thinking of this for a while. It will save lots on wear on the SSD pools.

Edited April 30, 20233 yr by Niklas

1 hour ago, Niklas said:

Would it be complicated to copy/move the docker-xfs.img to pool or array at shutdown and back again to ram at power up?

Consider this modification:

 

 

 

1 minute ago, mgutt said:

Consider this modification:

 

 

 

 

I have used your script for some time, thanks! 

 

It saves much but I still have several GBs written to cache pool every day (like 30+GB). Not counting any stuff affected by mover but I also have appdata on cache of course, but nothing that should write that amount every day.