bubblewrap

bubblewrap is the Linux namespace primitive behind Fence and many other sandboxes. Use it directly when you want a minimal DIY jail without Fence’s policy layer.

Install

# Debian / Ubuntu
sudo apt install bubblewrap

# Fedora
sudo dnf install bubblewrap

For a higher-level wrapper around per-project bubblewrap configs, see sandbox-run.

Launch with proxy env

Share the host network so the jail can reach varlock on loopback, bind your project read-write, and keep the rest of $HOME out:

eval "$(varlock proxy env)"

bwrap \
  --die-with-parent \
  --unshare-pid \
  --share-net \
  --ro-bind /usr /usr \
  --ro-bind /bin /bin \
  --ro-bind /lib /lib \
  --ro-bind /lib64 /lib64 \
  --ro-bind /etc /etc \
  --bind "$PWD" "$PWD" \
  --chdir "$PWD" \
  --dev /dev \
  --proc /proc \
  --tmpfs /tmp \
  -- claude

Adjust binds for your distro layout and tools (node, agent binaries under /home, etc.). Prefer Fence if you want packaged agent templates and domain allowlisting without maintaining a long bwrap line.