Environment variable for specifying custom system image (-J, --sysimage)

[tomyun]

There is no environment variable equivalent to -J/--sysimage option for specifying a custom image for Julia instance. I think supporting a variable like JULIA_SYSIMAGE can be quite useful when deploying Julia for custom environment, i.e. deploying in a Docker container with custom system image baked in.

Currently, one would have to manually add an option every time or create a wrapper script to launch Julia with custom image, especially when replacing default system image is not an option (i.e. repo2docker does not allow root privileges for touching system image when using default Julia buildpak).

[akosuas]

I'd also like this - I think it is a duplicate of #36843 though

[PallHaraldsson]

I'm not sure about this. Is it really useful? I'm thinking if someone can get to change my default shell environment, then they could trick me into running arbitrary code, right? Maybe I'm too paranoid and shouldn't worry about that. If that happens, then I guess I have bigger problems, and I should e.g. be able trust my system administrator (hackers could also change my code, but it would potentially be more obvious than with the env variable).

Maybe we already have this problem with LD PRELOAD, so might as well do this.

Isn't there a good workaround with using PackageCompiler.jl and/or "create a wrapper script to launch Julia with custom image"?

[vtjnash]

Most things do not need a environment variable duplicate