PEX_ROOT doesn't seem to be honoured for all directories.

[KatieLucas-Grapeshot]

After setting PEX_ROOT, pex still attempts to write to ~/.pex -- notably trying to create ~/.pex/interpreters.

This is a problem because on our build system the build process's users $HOME is non-writeable.

I suspect that the default values for the flags in pex.py lines 162 and 269 are at fault here; expanding to the $HOME regardless of the PEX_ROOT setting.

(For the time being have worked round this by setting flags explicitly.)

Thanks,
Katie

[jsirois]

Sorry for the huge delay, but this issue has been revived through a reference.

How do you set PEX_ROOT? NB: A very confusing aspect of pex is its build time vs runtime behavior.

At build time, if you set PEX_ROOT as an env var or pass the --pex-root flag to the cli, you only set the PEX_ROOT for the build process and not for the runtime of the resulting pex when executed. The pex --help hints at this:

$ pex --help
...
  --pex-root=PEX_ROOT   Specify the pex root used in this invocation of pex.
                        [Default: ~/.pex]
...

So, to set PEX_ROOT at runtime you need to do one of:

1. Ensure the desired PEX_ROOT environment variable is exported.
2. Set PEX_ROOT inline if using a shell like bash; ie PEX_ROOT=x ./my.pex ...
3. Deploy appropriate pexrc files on target machines. These can be in 3 locations:
   1. sibling to the pex file being run in .pexrc
   2. in ~/.pexrc
   3. in /etc/pexrc
      Line in pexrc are env-var lines like PEX_ROOT=y and they are read and applied with the precedence above, a sibling .pexrc having the highest precedence.

We currently offer no option to embed the PEX_ROOT setting in the pex at build time since pexes are generally non-machine specific - they can run anywhere; so the PEX_ROOT embedded in the pex if we supported this might not exist or be appropriate on some target hosts.

[jsirois]

I'm going to close this as answered, but if the above explanation is unclear or unsatisfactory for your usecase, please re-open.