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What is the easiest way to persist data to disk within a unikernel ?

For now, you need to write your unikernel against the FS signature[1], with its corresponding fs[2] combinator in the Mirage DSL. The only integrated backend for this is fat (i.e. using the`fat_of_files` or `fat` combinators).

An Irmin backend is on its way, although it might come with a simpler KVmodule type (which might look lile this one[3]). If you are using the mirage-dev repository you'll be able to use Irmin+Git on Xen, with a minimal KV_RO integration (see the relevant discussion on GitHub[4]) - extending this with a write function which would push any change to a remote Git repository is not very difficult to do, although my focus now is to integrate the current patches properly.

Best,

Thomas

[1]: http://mirage.github.io/mirage/V1.FS.html

[2]: http://mirage.github.io/mirage/Mirage.html#TYPEfs

[3]: http://erratique.ch/software/tick/doc/Tick.KV.html

[4]: https://github.com/mirage/irmin/issues/107#issuecomment-121500710

For instance let's imagine I would like to write a unikernel that holds a list of RSS feeds and routinely checks for updates.
I could hold this in memory but how to persist the changes so it survives a restart ?

A key-value store would do. Can Irmin be used within a unikernel ? Is there any existing code I could look at ?

The only example of writing to disk I am aware of is Thomas Leonard blog post: http://roscidus.com/blog/blog/2014/07/28/my-first-unikernel/
But this quite involved and maybe out of date...

Thank you

Manu
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