improved fs_rom

[Norman Feske]

Hello Ben,

> Also, how well does the vfs server handle config updates?

the VFS does not support dynamic reconfiguration. (yet)
 > Can you give me more
> details on the status of the vfs in that regard? Specifically, how
> does it handle duplicates and writing?

The order of sub nodes within the top-level <vfs> node and within <dir>
nodes defines how content is shadowed.

The VFS does not support copy-on-write. A file provided by a read-only
file system will stay read only and cannot be changed. However, we plan
to supplement copy-on-write support as a plugin later. Until then, the
use case of providing an initial version of a config file that can be
modified at runtime cannot be covered by the vfs. Here, we still have to
use the ram_fs loaded with initial <content>.

> Which filesystem/plugin
> provides the file? And which one is written to when a new file is
> created?

A new file is created on the first writeable file system mounted at the
directory hosting the new file.

You may experiment with the VFS using a <ram> file system as a writeable
file system and <tar> file systems for read-only content. You may also
find the various noux scenarios worth looking at because they all use
the VFS. In particular, they mount multiple tar archives at '/' where
each tar archive contains a '/bin' directory. In the VFS, the joint
content of all archives becomes visible.

Cheers
Norman

-- 
Dr.-Ing. Norman Feske
Genode Labs

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