Unable to write to a container

[sushma-98]

Version of Singularity:

3.1-2

Expected behavior

Being able to write to the container after executing it with -w flag.

Actual behavior

WARNING: While attempting to set up SIFOverlay: no SIF writable overlay partition found
ERROR: Unable to lock database: Read-only file system
ERROR: Failed to open apk database: Read-only file system

Steps to reproduce behavior

sudo singularity exec -w alpine_3.9.2.sif apk add htop

[cclerget]

@sushma-98 It's the expected behaviour since SIF doesn't contain an overlay partition, actually singularity can handle this case but you need to manipulate your SIF image manually with siftool to make SIF image writable. By default SIF image contains only a squashfs filesystem partition, and squashfs is a read-only filesystem, you need to use --writable-tmpfs or a sandbox image. Closing the issue.

[sushma-98]

Thank you @cclerget Can you please give an example where -w is used? I have to test the -w flag