Re: How to roll back a "guix system reconfigure"?

[ludo@gnu.org (Ludovic Courtès)]

Alex Kost <alezost@gmail.com> skribis:

> Chris Marusich (2016-04-02 22:20 +0300) wrote:
>
>> Hi,
>>
>> After running a "guix system reconfigure", it is possible to boot to a
>> previous version of the system by manually selecting it from the GRUB
>> menu.  However, if you want to permanently roll back to a previous
>> version (e.g., because something broke), it's a nuisance to do this
>> every time you boot.  Of course, assuming guix is still working after
>> the reconfigure, you could simply do another "guix system reconfigure"
>> using the previous version of your operating system configuration file,
>> but it seems like that shouldn't be necessary.
>>
>> What is the recommended way to roll back after a "guix system
>> reconfigure"?  Is it sufficient to manually edit the grub.cfg file to
>> remove all mention of the generations after the one to which you want to
>> roll back?  If you do that, will the gc root(s) associated with the bad
>> configuration stay around forever?  Would it make sense to add a command
>> like "guix system roll-back" or "guix system switch-generation", similar
>> to "guix package --roll-back" and "guix package --switch-generation"?
>
> Yes, I think these things will be added eventually.  It's just that no
> one has not been interested enough in these features yet to add them.

Indeed, but these are definitely things we should add!

> Currently there are 2 ways to perform a system roll-back:
>
> 1. Manually: system generations are just symlinks in "/var/guix/profiles"
> directory, so you can change "/var/guix/profiles/system" link to point
> to any previous generation.
>
> 2. Using Emacs interface (you have to run emacs as root):
>
>  - M-x guix-system-generations;
>  - Press "c" on a generation you want to make current.

There’s also a 3rd way to temporarily roll back: from the GRUB menu,
select one of the previous generations (very useful for the occasional
mistake you make when reconfiguring into a somewhat experimental
config!).

Ludo’.