as_uid

Gem utility made to run code as another user

Summary

When you have a system administration or automation task and you decide to write a Ruby script that runs as root, but you need to take some actions on behalf of another user (e.g. run an external program or create a file).

Installation

Install gem:

gem install as_uid

Or build locally and install:

gem build as_uid.gemspec
gem install ./as_uid-0.0.3.gem

Basic usage examples

Imagine that on your system the account user has UID 1000. When run as root, this code will create one directory owned by root and one owned by user:

Dir.mkdir("as_root")

Process.as_uid(1000) do
  Dir.mkdir("as_user")
  %x{whoami}
end
# => "user\n"

Here are the directories:

$ ls -ld as_*
drwxr-xr-x 2 user root 4096 Feb 2 13:06 as_user/
drwxr-xr-x 2 root root 4096 Feb 2 13:06 as_root/

When you’re switching to another user, your permissions are restricted to what that user can do. We can’t remove the as_root directory as a nonroot user (with custom user), because I created it as root:

Process.as_uid(1000) do
  Dir.rmdir("as_root")
end
# Errno::EPERM: Operation not permitted - as_root
Dir.rmdir("as_root") # => 0

Tests

To run tests use following command:

sudo rake test

Note: You should use sudo because root privileges are expected in test scenarios.

Binary script

Example run of binary script:

ruby -Ilib ./bin/as_uid 1000 "mkdir 123"

License

MIT licensed library. See LICENSE for details.

Contributing

If you have suggestions for improving the as_uid, please open an issue or pull request on GitHub.

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