Use unshare --mount in a docker executor?

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Hello,

We have a use case to run an executable under test in its own mount namespace due to use of a static directory that cannot be changed. We have the following wrapper:

#!/bin/sh
mkdir -p <static-directory>
mount --bind $TEMPORARY_DIRECTORY <static-directory>
exec <executable-under-test>

and we can run it with sudo unshare --mount <wrapper>. However the unshare command fails with unshare: unshare failed: Operation not permitted

I am aware of How CircleCI handles security - CircleCI, and I am wondering how it can be achieved on CircleCI with docker executors. Machine executors is an over-kill…

Regards,
Boris.