Bug#757298: upgrades must not change the installed init system [was: Re: Cinnamon environment now available in testing]

[Carlos Alberto Lopez Perez]

On 09/09/14 15:14, Mathieu Parent wrote:
> 2014-09-09 13:46 GMT+02:00 Carlos Alberto Lopez Perez <clopez at igalia.com>:
> [...]
>> So, when upgrading from Wheezy to Jessie, we have three options:
>>
>> 1) Keep the user init system (sysvinit most probably)
>> 2) Upgrade to systemd after asking the user.
>> 3) Upgrade to systemd silently without asking the user.
> 
> 4) Upgrade to systemd silently without asking the user AND add a grub
> entry to use old init
> 
> This will provide the intended default with an extra compatibility
> layer (like the former grub1 to grub2 chain).
> 

This may be a good option when you have pre-boot access to the machine
(either physical access or with a KVM), so you can select an option on
the GRUB menu if things go wrong.

But if you don't (Is not uncommon to have servers on remote locations
that are only accessible via ssh) and the machine don't boots properly
you can find yourself in trouble.

When the transition to GRUB2 was made, it didn't replaced the previous
system (GRUB1) without asking the user. What it did was to add a new
(non default) entry on GRUB1 to chainload to GRUB2. The idea was that
the user could test the new system when he felt it was a good moment.
So, after checking that all worked as expected, he could make the new
system the default by executing a command: upgrade-from-grub-legacy. [1]


I wish something similar would be made for the switch to systemd:

1. Add a new entry on GRUB to boot with systemd (but leave the previous
init system as default).
2. Add a command upgrade-from-init-legacy or upgrade-to-systemd that
sets the option to boot with systemd as default.

That way the user can test to boot with systemd when he feels like is a
good moment, and if things work as expected he can make the switch
definitively by executing that command.





[1] https://wiki.debian.org/Grub#Upgrading_from_v1_to_v2

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