On 10/23/2015 05:45 PM, Yamaban wrote:> Well, looking back, during kernel 2.6 there was no systemd at all.
> But! That was the time where udev and dbus came into the boot cycle.
> ...
> What was the rationale to get udev into boot? -- Handling the ever
> changing mess of plugable, switchable hardware. Not born and bred
> for servers, but for mobiles (phones, tablets, laptops).
> ...
> What was the rationale to let dbus near the system start at all?
> -- Again mobile development.
>
Was it? Many servers are deployed as standard images, both physical and
virtual, and having a single, standard, cloned image boot easily on
multiple types of hardware makes lots of sense in this environment.
Dbus is about hardware enumeration, both cold and hot plug. And there
are servers with hotplug PCIe, even hotplug CPU's. Dbus makes hotplug
HDD support smoother, for instance, and hotplug isn't limited to USB or
firewire (eSATA and external SAS, even fibre channel, can be hotplugged
in most cases).
I still remember having to rebuild initrds when moving a clone from a
server with one type of disk controller to another. It should work a
lot better with dynamic hardware detection in the initrd. (I wont's say
it's prefect, because I haven't personally tried every possible
combination of hardware, but it has worked lately when I needed it to work.)
A SAN storage processor, for instance, must be able to hotplug drives,
enclosures, front end and back end interfaces, power supplies, and
sometimes even processors while staying up.
> Systemd was just the latest development, and not the worst. Yes, it
> could have gone better, and some of the devs have had more
> head-in-the-clouds than feet-on-the-ground.
>
> Looking back, systemd is the only "big" change since 2.6 that
makes
> sense for servers. ...
I would agree.
> What was the jump forward for linux servers in this 16 years?
Better hardware support, ease of virtualization (as a guest and as a
host), and dynamic hardware detection for rapid redeployment/hardware
upgrade, just to mention three.
