[Devel] Re: restart (mktree) program usage

[Sukadev Bhattiprolu]

Oren Laadan [orenl at librato.com] wrote:
| 
| 
| Sukadev Bhattiprolu wrote:
| > I have a usage question on the 'restart' (formerly mktree) program.
| > 
| > In the following container c/r case: 
| > 
| > 	- create a container
| > 	- log in to the container,
| > 	- restore filesystem(s) from snapshot
| > 	- restart application from checkpoint
| 
| FWIW, I'd expect that future versions of 'restart' will be capable
| of doing this entire setup, (filesystem(s) included), as it matures.
| 
| Note that this use case that you suggest will only work to restart
| subtrees; it is unsuitable for full containers (with pids) because
| the pid of init (1) will already be in use.

True. But if originally the application was started as:

	Create container
	Login to contaienr
	Set up filesystem
	Start application

The application would not be using the pid 1 right - even if the
application was started from an rc script in the container ?

| 
| Perhaps we should think of some "plugin" architecture for 'restart'
| that will allow the user to ask it to execute some work at between
| creating a new container and actually restarting into it ?

Yes, that would be really useful I think for things like restoring file
system to its snapshot. Without that there is somewhat of an assymetry
in starting an application in a container and restarting it from a
checkpoint.
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