[[!template id=project

title="Add snapshots to tmpfs"

contact="""
[tech-kern](mailto:tech-kern@NetBSD.org)
"""

category="filesystems"
difficulty="medium"

description="""
Add memory-efficient snapshots to tmpfs.  A snapshot is a view of the
filesystem, frozen at a particular point in time.  The snapshotted filesystem is
not frozen, only the view is.  That is, you can continue to
read/write/create/delete files in the snapshotted filesystem.

The interface to snapshots may resemble the interface to null mounts, e.g.,
'mount -t snapshot /var/db /db-snapshot' makes a snapshot of /var/db/ at
/db-snapshot/.

You should exploit features of the virtual memory system like copy-on-write
memory pages to lazily make copies of files that appear both in a live tmpfs and
a snapshot.  This will help conserve memory.
"""
]]