Re: Gentoo for many servers (was: Re: [gentoo-user] executing commands on lots of servers at once)

[Alan McKinnon]

On Saturday 14 November 2009 19:36:06 Alex Schuster wrote:
> Alan McKinnon wrote:
> > clusterssh will let you log into many machines at once and run emerge
> >  -avuND world everywhere
>
> This is way cool. I just started using it on eight Fedora servers I am
> administrating. Nice, now this is an improvement over my 'for $h in
> $HOSTS; do ssh $h "yum install foo"; done' approach.

I feel your pain :-)

We used to have the same problem adding new admins to 87 machines. Now we have 
a bespoke provisioner that does it all.

> What do you guys think about using Gentoo for servers? At the institute I
> partially work we chose Fedora. There is no special reason for that - we
> already had some Fedora machines, the setup seemed to work, the reputation
> was good, so we kept it. That was okay for me, why choose many different
> environments and learn everything again. I mentioned Gentoo, but did not
> really suggest to actually use it. Maybe I should have.

I'm a huge fan of Gentoo and all my personal machines (except the new netbook) 
have run it for the last 5 years.

But I will never install Gentoo on a production server at work.

Why?

Because it is too time consuming, because no two machines are set up the same, 
because I can't trust that other admins used the flags they should have. So 
updates become a case of logging into 80+ machines individually and doing 
emerge world by hand. Gentoo allows you to customize things to the nth degree 
- that is it's strength - so people WILL use this one discriminating factor.

If OTOH I had a server farm of 80+ machines, all identical, I'd put Gentoo on 
them in a flash. But I don't have that
 
> These 8 servers I mentioned are basically clones of the one I installed
> manually. Instead of doing this again, I boot a live-cd on a new one,
> create partitions, and extract tar files of the first server's partitions.
> Then I do some extra configuration, like hostname and network setup. Done.
>
> My plan for updating them is to take the first server down, and upgrade
> the installation (if that works - I had some trouble with that before, so
> maybe it will be better to reinstall from scratch). Then I will create a
> snapshot of the new setup, transfer that to the other hosts, and unpack it
> in new logical volumes. I plan to script this so I do not have to do it
> manually every time - but that was before I knew ClusterSSH. When all is
> done and there is some time to take the servers down, I will reboot into
> the new system.
>
> Now I am thinking about a Gentoo installation instead.
>
> Pros:
>  - Continuous updates, no downtime for upgrading, only when I decide to
> install a new kernel. This is really really cool. I fear the upgrade from
> Fedora 10 to 12 which has to be done soon.

Do not upgrade, especially not with a version jump of 2 or more. If you have a 
lot of machines, I assume you are a decent shop, and that you have some form 
of formal process for upgrades and changes.

What you do instead is a formal migration - copy the data off, reinstall, 
restore data. If you can't afford to do that every six or twleve months, then 
I have to ask - what the hell is the organization doing using a distro that is 
unsupported after 12 months?

>  - Some improvement in speed. Those machines do A LOT of numbercrunching,
> which jobs often lasting for days, so even small improvements would be
> nice.

Don't fool yourself. Unless you need what Google needs, there is very little 
speed difference between Gentoo and Fedora. I/O improvements you need can be 
easily gotten by fiddling the kernel tuning knobs.

>  - Easier debugging. When things do not work, I think it's easier to dig
> into the problem. No fancy, but sometimes buggy GUIs hiding basic
> functionality.

Errrrrrrrrrrrrrrrmmmmmmmmmmmmmm, Fedora does not require a GUI :-)

>  - Heck, Gentoo is _cooler_ than typical distributions. And emerging with
> distcc on about 8*4 cores would be fun :)

Can't argue with that.

But that is your ego talking and the machines do not belong to you but to the 
institute. Your ego has no place in that.

>  - I am probably the only one who can administrate them.

This is not a benefit. It is a severe liability.

Where I work, I get fired for trying that :-(

> Cons:
>  - If something will not work with this not so common (meta)distribution,
> people will say "always trouble with your Gentoo Schmentoo, it works fine
> in Fedora". Fedora is more mainstream, if something does not work there,
> then it's okay for the people to accept it.

Those same people are likely to say the same about linux vs windows.

>  - I fear that big packages like Matlab are made for and tested on the
> typical distributions, and may have problems with the not-so-common
> Gentoo. I think someone here just had such a problem with Mathematica
> (which we do currently not use).

One or two persons had problems. Many many more replied that they had no 
problems at all. In Fedora-land, the ratio is the same.

>  - I am probably the only one who can administrate them. I think Gentoo is
> easier to maintain in the long run, but only when you take the time to
> learn it. With Fedora, you do not need much more than the 'yum install'
> command. There is no need to read complicated X.org upgrade guides and
> such.
>
> I think I already made my decision, but I am still interested in your
> opinions, maybe some of you are in a similar position and like to share
> your experiences. Whether I will be allowed to use Gentoo is another
> question, I guess my boss will not like my idea at first, and I am not
> even sure if he is right. But maybe I can test-install Gentoo on one
> machine in a chroot, and see if things work fine.

Depends how critical these machines are. If you want to change them just 
because you feel like it, then I do not see how that can possibly be a valid 
reason. 

Remember, the institute's needs and desires trump yours every time

-- 
alan dot mckinnon at gmail dot com