Minimum RAM requirement for building

[verdurin]

Version of Singularity:

2.5.1

Expected behavior

Singularity should complain if there is an attempt to build when there isn't sufficient memory on the build host.

Actual behavior

Lots of errors, including:

Warning handling tar header: Write failed
tar extraction error: Write failed

and later on:

cp: error writing '/var/singularity/mnt/container/etc/resolv.conf': No space left on device

which is what led me to suspect lack of RAM.

Steps to reproduce behavior

Build container from

https://github.com/rses-singularity/tfgpu-theano-pytorch-keras

in Fedora 27 VM with 2GB RAM.

Build fails.

Reconfigure VM with 4GB RAM.

Build succeeds.

There isn't necessarily a fix here, but it would be helpful if Singularity could be clearer about the problem when it occurs.

[cclerget]

@verdurin Singularity use /tmp as temporary folder to build image, so your /tmp directory is a RAM filesystem like tmpfs. By default tmpfs use almost 50% of total memory, which could explain why after growing VM memory build succeed. Singularity doesn't have RAM requirements for builds, you can use another directory other than /tmp by setting SINGULARITY_TMPDIR environment variable like this :

$ SINGULARITY_TMPDIR=/var/tmp singularity build image.simg Singularity

Between it could be difficult to catch the error because exit code doesn't necessary reflect the error code of command

[verdurin]

@cclerget yes, I know it's not an easy one to handle. Maybe it's worth mentioning this in the documentation?

[cclerget]

@verdurin You're right, we can mention this kind of error in the documentation

[dtrudg]

Still need to mention tmpfs in docs nicely.