Host files

Machines that are not isolated see three host trees, read-write, at /mnt/host followed by their host path:

Host	In a machine
Your home, such as /var/home/you	/mnt/host/var/home/you
/run/media/you	/mnt/host/run/media/you
/mnt	/mnt/host/mnt

Nothing else from the host is shared: not /usr, /etc, /tmp, the rest of /run, or any pseudo-filesystem. Sharing is per machine, never per project, and every machine that is not isolated sees the same trees.

Paths and aliases

Translation is a prefix: host path P is /mnt/host/P in a machine. nsl matches your working directory by device and inode, so symlinked and bind-mounted aliases translate too. On atomic hosts, /home is often a link to /var/home; the machine gets a matching relative link, /mnt/host/home → var/home, so both spellings work.

Every machine image includes nsl-path for scripts that pass paths between the two sides:

nsl-path /mnt/host/var/home/you/notes.md   # → /var/home/you/notes.md
nsl-path --guest /var/home/you/notes.md    # → /mnt/host/var/home/you/notes.md

Without a flag, a path under /mnt/host becomes a host path and any other absolute path becomes a guest path. Relative paths start from the current directory.

Ownership and permissions

Files created through /mnt/host belong to you on the host. The share runs with your host user's permissions, so root in a machine cannot do anything to your files that you could not.

What does not cross

• Unix sockets. Sockets under a shared tree do not connect across the share. D-Bus, SSH agent, GPU and display sockets are never shared.
• File events from the host. Edits made on the host produce no inotify events in machines, as with WSL's /mnt/c. File watchers, hot reload and watched builds belong in the guest home. Edits between machines do produce events, because machines share one kernel.
• Automounts. A host automount point that is not mounted yet appears empty in machines until the host mounts it.

Isolated machines

Isolated machines see none of these trees. Their working directory never translates: a shell starts in the guest home, and run needs --cd.

What this means for trust

A machine that can write your home can change your shell startup files, keys and nsl's own state. That is the model: a machine is trusted as you. The trust model explains why there is no read-only tier, and when to use --isolated instead.