try

"Do, or do not. There is no try."

We're setting out to change that.

Description

try lets you run a command and inspect its effects before changing your live system. try uses Linux's namespaces (via unshare) and the overlayfs union filesystem.

Please note that try is a prototype and not a full sandbox, and should not be used to execute commands that you don't already trust on your system, (i.e. devices in /dev are mounted in the sandbox, and network calls are all allowed.) Please do not attempt any commands that will remove everything in /dev or write zeros to your disks.

Getting Started

Dependencies

Has been tested on the following distributions:

• Ubuntu 20.04 LTS or later
• Debian 12
• Centos 9 Stream 5.14.0-325.el9
• Arch 6.1.33-1-lts
• Alpine 6.1.34-1-lts
• Rocky 9 5.14.0-284.11.1.el9_2
• SteamOS 3.4.8 5.13.0-valve36-1-neptune

Installing

You only need the try script, which you can download by cloning this repository:

$ git clone https://github.com/binpash/try.git

Arch Linux

Try is present in AUR, you can install it with your preferred AUR helper:

yay -s try

or manually:

git clone https://aur.archlinux.org/try.git
cd try
makepkg -sic

Example Usage

try is a higher-order command, like xargs, exec, nohup, or find. For example, to install a package via pip3, you can invoke try as follows:

$ try pip3 install libdash
... # output continued below

By default, try will ask you to commit the changes made at the end of its execution.

...
Defaulting to user installation because normal site-packages is not writeable
Collecting libdash
  Downloading libdash-0.3.1-cp310-cp310-manylinux_2_17_x86_64.manylinux2014_x86_64.whl (254 kB)
     ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 254.6/254.6 KB 2.1 MB/s eta 0:00:00
Installing collected packages: libdash
Successfully installed libdash-0.3.1
WARNING: Running pip as the 'root' user can result in broken permissions and conflicting behaviour with the system package manager. It is recommended to use a virtual environment instead: https://pip.pypa.io/warnings/venv

Changes detected in the following files:

/tmp/tmp.zHCkY9jtIT/upperdir/home/gliargovas/.local/lib/python3.10/site-packages/libdash/ast.py (modified/added)
/tmp/tmp.zHCkY9jtIT/upperdir/home/gliargovas/.local/lib/python3.10/site-packages/libdash/_dash.py (modified/added)
/tmp/tmp.zHCkY9jtIT/upperdir/home/gliargovas/.local/lib/python3.10/site-packages/libdash/__init__.py (modified/added)
/tmp/tmp.zHCkY9jtIT/upperdir/home/gliargovas/.local/lib/python3.10/site-packages/libdash/__pycache__/printer.cpython-310.pyc (modified/added)
/tmp/tmp.zHCkY9jtIT/upperdir/home/gliargovas/.local/lib/python3.10/site-packages/libdash/__pycache__/ast.cpython-310.pyc (modified/added)
<snip>

Commit these changes? [y/N] y

Sometimes, you might want to pre-execute a command and commit its result at a later time. Running try -n will print the overlay directory on STDOUT without committing the result.

$ try -n "curl https://sh.rustup.rs | sh"
/tmp/tmp.uCThKq7LBK

Alternatively, you can specify your own existing overlay directory using the -D [dir] flag:

$ mkdir rustup-sandbox
$ try -D rustup-sandbox "curl https://sh.rustup.rs | sh"
$ ls rustup-sandbox
temproot  upperdir  workdir

As you can see from the output above, try has created an overlay environment in the rustup-sandbox directory.

Manually inspecting upperdir reveals the changes to the files made inside the overlay during the execution of the previous command with try:

~/try/rustup-sandbox/upperdir$ du -hs .
1.2G    .

You can inspect the changes made inside a given overlay directory using try:

$ try summary rustup-sandbox/ | head

Changes detected in the following files:

rustup-sandbox//upperdir/home/ubuntu/.profile (modified/added)
rustup-sandbox//upperdir/home/ubuntu/.bashrc (modified/added)
rustup-sandbox//upperdir/home/ubuntu/.rustup/update-hashes/stable-x86_64-unknown-linux-gnu (modified/added)
rustup-sandbox//upperdir/home/ubuntu/.rustup/settings.toml (modified/added)
rustup-sandbox//upperdir/home/ubuntu/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/libstd-8389830094602f5a.so (modified/added)
rustup-sandbox//upperdir/home/ubuntu/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/etc/lldb_commands (modified/added)
rustup-sandbox//upperdir/home/ubuntu/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/etc/gdb_lookup.py (modified/added)

You can also choose to commit the overlay directory contents:

$ try commit rustup-sandbox

Known Issues

Any command that interacts with other users/groups will fail since only the current user's UID/GID are mapped. However, the future branch has support for uid/mapping; please refer to the that branch's readme for installation instructions for the uid/gidmapper.

Please also report any issue you run into while using the future branch!

Version History

• 0.1.0 - 2023-06-25
  • Initial release.

License

This project is licensed under the MIT License - see LICENSE for details.

Copyright (c) 2023 The PaSh Authors.