subsystemd: Run systemd in WSL2

Run systemd under Linux namespace in WSL2. Heavily inspired by arkane-systems/genie, but written in Rust.

Difference with arkane-systems/genie

Slightly following [genie]'s behavior, but noted below...

• Interface
  • Command line interface is not compatible.
• Behavior
  • Hostname altertion is optional with --hostname, --hostname-suffix
  • /etc/hosts are not updated. Users are encouraged to use nss-myhostname.
  • Uses machinectl shell to launch a user shell; this allows running systemd user session
• Internal
  • Removed dependency to unshare, daemonize, nsenter command line tools
  • systemd-wide environment variables are set via systemd.conf drop-in, using DefaultEnvironment=
  • systemd PID from root namespace is stored at /run/subsystemctl/systemd.pid

Install

Arch Linux AUR

https://aur.archlinux.org/packages/subsystemctl

Self build

bash cargo build --release install -m6755 -oroot -groot ./target/release/subsystemctl /usr/local/bin/subsystemctl

Usage

subsystemctl start: Start systemd environment

ps1 PS> wsl -u root -- subsystemctl start

subsystemctl shell: shell login to systemd-enabled environment

ps1 PS> wsl subsystemctl shell Connected to the local host. Press ^] three times within 1s to exit session. someone@hostname$ ...

Specifying uid to login

ps1 PS> wsl -u root -- subsystemctl --uid=1000 shell Connected to the local host. Press ^] three times within 1s to exit session. someone@hostname$ ...

subsystemctl exec: Raw nsenter like interface

ps1 PS> wsl subsystemctl exec id uid=1000(sorah) gid=1000(sorah) groups=1000(sorah),116(admin)

Specifying uid (and gid)

```ps1 PS> wsl -u root -- subsystemctl exec id uid=0(root) gid=0(root) groups=0(root)

PS> wsl -u root -- subsystemctl exec --uid=1000 id uid=1000(sorah) gid=1000(sorah) groups=1000(sorah),116(admin)

PS> wsl -u root -- subsystemctl exec --uid=1000 --gid=116 id uid=1000(sorah) gid=116(admin) groups=116(admin) ```

subsystemctl is-running

```bash

!/bin/bash

if subsystemctl is-running; then echo "running" else echo "not-running" fi ```

subsystemctl is-inside

```bash

!/bin/bash

if subsystemctl is-inside; then echo "inside" else echo "outside" fi ```

Tips

systemd-resolved, networkd are recommended to be disabled

otherwise /etc/resolv.conf might get overwritten to resolved stub-resolver.

Author

Sorah Fukumori https://sorah.jp/

License

MIT