Re: [gentoo-dev] eselect init

[Luca Barbato <lu_zero@gentoo.org>]

On 5/26/13 8:43 AM, Michał Górny wrote:
> On Sat, 25 May 2013 11:54:48 +0200
> Luca Barbato <lu_zero@gentoo.org> wrote:
>
>> - /sbin/init (or whatever linux currently calls by default with top
>> priority) should be either a symlink to the actual implementation or a
>> wrapper such as our gcc one. I like better the latter since it is
>> overall safer. The former might or might work since linux has some
>> fallback capabilities but hadn't been tested.
>
> Increased complexity is never safer. And a wrapper means the additional
> complexity gets there every boot. And considering how the discussion
> goes, the wrapper will grow openrc-size in a few months...

Openrc is small, but the wrapper really needs to know which is which and 
worst case switch inittab.

> Symlinks are simple. They're filesystem feature, they're handled
> by kernel. The worst thing that could happen is symlink target
> disappearing -- but then it's:
>
> a) our responsibility to make sure to call eselect-init (if applies)
> when uninstalling an init system,
>
> b) something that would fail anyway if user did that by hand.
>
> Linux fallback mechanism is *good enough*. You may think that fallback
> to sysvinit is good but it's not. *If* I have my system set up to boot
> X, at some point the config for Y will get seriously outdated.

Have you tested it? Do you know what is the reaction of do_exec on a 
dangling symlink?

> I use systemd for a few months now, and last time I checked openrc
> boots somehow. But considering the general complexity of it, I wouldn't
> be much surprised if it failed in funny ways (like not being able to
> handle automounts properly), caused cruft on the filesystem or even
> caused *damage*.

openrc is *simpler* much *simpler* than systemd, stop with that.

> And since you've been failing long at keeping init.d scripts simple
> and reasonable, the damage potential is not something purely
> theoretical.

wc -l is a good answer to your concern. Some scripts have to be 
simplified, that's a given (e.g. Fabio pointed the lvm one can be 
improved a lot) but it isn't the case for most of them.

> Pointless and overcomplex. If an init system actually fails to work
> when /sbin/init doesn't point to it, it is seriously broken by design.
> And because of that breakage, we keep stuff like 'telinit' or 'reboot'
> intact, and because of it systemd has 'pass-through' mode when linked
> to /sbin/init.

Check your facts, systemd either understands a flavour of inittab or the 
other or none at all.

> Which means the kernel fallback will be dangerously active
> as I explained before. Just don't do it.

It is not dangerous beside for those that have an inittab with rm -fR /

lu