Create VOD or save stream to disk

While livestreaming from/to RTMP or HLS, is it possible to save the incoming livestream as a VOD or simply a mp4 file to DISK, whether for use as a backup or further use as a VOD or just to provide a "download" to the user at later date.

Nimble Streamer doesn't currently have DVR capabilities, but this feature is under development right now. It's planned to be released in the next few months.
I don't have ETA but you will see all possible love in this functionality and even more. Sorry for waiting but we always wait something we love then for a long time:)

Even though you don't have a exact ETA, is there any expected timeline, like 3 months or 6 months, since once you start using a engine at the core of your platform, its really hard to make a switch to something else and video backup or VOD is something which is needed in our proposed product/platform plan.

Secondly, is there currently any alternative or "ssh/root" way to do this via server itself, like if there is any pipeline available for incoming stream, we can use FFMPEG to write it to disk for time being.

We are going to release first working version of DVR feature by the end of this year.

Meanwhile you can use ffmpeg to write on disk. You can also control your ffmpeg using our Server-side tasks control feature:
http://blog.wmspanel.com/2014/10/server-tasks-web-management.html