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Why Fedora?

Why Fedora?

Posted Jul 26, 2009 20:59 UTC (Sun) by jlokier (guest, #52227)
In reply to: Why Fedora? by epa
Parent article: A update

Those "odd bits of configuration" can add up to a lot of work, if you're running a lot of different things on your servers.

Which creates a dilemma, if you need a newer OS for some service but don't want to break the other services by doing the upgrade.

VMs help a lot with this, but they take a lot of resources and can't always be used.

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Why Fedora?

Posted Aug 1, 2009 10:12 UTC (Sat) by Lennie (guest, #49641) [Link]

Can I suggest Linux-VServer, it hardly uses any resources.

Why Fedora?

Posted Aug 1, 2009 14:16 UTC (Sat) by jlokier (guest, #52227) [Link]

Linux-VServer and it's apparent successor LXC are much better for resource usage than KVM, it's true.

There is that slight problem that you don't have different kernels under Linux-VServer, so older distros which break with later kernels won't work. The kernel's system call interface is backward compatible, but many other things which "system-level" utilities depend on are not, and those are needed to boot an old distro without spending lots of time tweaking it.

So, not so good for booting old distros, but fine for running applications on those distros provided they don't depend on a booted environment. E.g. it's great for running old versions of GCC.

What KVM is great for is taking an old, working machine (say using a Linux 2.4 kernel or earlier, or Windows of course) and migrating it into KVM on a new machine with almost no work at all.

So: KVM for old Linux images and other OSes where you need a fully booted environment; Linux-VServer or LXC for almost current images, or running applications on old images which don't need a booted environment.

Why Fedora?

Posted Aug 1, 2009 18:47 UTC (Sat) by Lennie (guest, #49641) [Link]

I have a feeling you already know this, but just in case:

Actually, most VServers don't need much boot and/or system-level stuff.

You could say it runs only starts/runs those scripts which usually get run at init level 2 or 3.

VServers don't handle anything them selfs, like mounting /tmp or setting up networking. The /dev directory is mostly empty only null and zero and stuff like are needed.

Yes, going from physical to vserver might be more work (stripping out stuff you don't need). I've never seen any problems with kernel-dependencies.

Why Fedora?

Posted Aug 2, 2009 5:29 UTC (Sun) by jlokier (guest, #52227) [Link]

Exactly. For running things which don't need a boot environment, and don't need system daemons like hald and D-Bus running, VServer is pretty good. Running old GCCs falls into that category. (I hope it stays that way).

It's also fine if you already have your apps set up to use it, naturally.

When it's less inviting is when the problem is to keep some old app working that's currently on a real machine running some old distro. KVM is quite good at making that work with minimal effort.

I put mail serving (anything other than a simple configuration) in the latter category, because these days a mail server is a fairly complex affair and will run alongside a couple of spam filtering daemons and virus filtering daemon and some delivery program or other, maybe also user's procmails and perhaps involving the IMAP service too, and undoubtedly depends on a few non-obvious files in /etc as well as the obvious ones. That's the sort of thing I mean by "if I don't have time to touch this now, I can't afford to be updating the OS on this server to a newer version". Repeated prior experience tells me such things break on OS upgrades and can take a long time to get working again with the same behaviour as before.

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