upgrade?

[Rick Stevens]

On Mon, 2007-04-16 at 15:52 -0700, chuck lawrence wrote:
> I must be missing something...
> 
> I want to upgrade es3 to es4, or centos4.2 to centos4.4.  I have almost 
> no config invested in either box (apps and user dirs come from nfs), so 
> a clean install is a viable option.  indeed, it's what I've always done.

Whoa!  An upgrade from ES3 to ES4 is a MAJOR upgrade (going from a 2.4
kernel to a 2.6 kernel, sysfs to udev and a raft of other things).
Something of that magnitude is usually best done through a fresh
install.  You can keep the users' home directories and such, but the OS
should be wiped.

Upgrading from CentOS 4.2 to 4.4 is a fairly minor update (equivalent to
upgrading from ES4 Update 2 to ES4 Update 4).

> but I could upgrade instead, right?  the first prompt says something 
> about "install or upgrade".

That's correct.

> o  can I upgrade while the os is running, as I can do with a kernel?

It's possible, but I wouldn't.  Any upgrade (note "upgrade" versus
"update") is probably best done on a quiescent system, and off the
install media.  Also note that the FIRST thing you should do when the
new, upgraded system comes up is to update it with current updates.
Media always lags behind the current updates.

> o  can I upgrade by booting from install media?

Yes.  Boot from the install media.  It will ask you if you want to
upgrade an existing version or install a new one.  This is true of both
ES and CentOS.

> o  is there any difference between upgrading like this and just keeping
>     packages up2date and then updating the kernel?

Yes, there are.  Again, ES3 (based on Fedora Core 1) is a completely
different beast than ES4 (based on Fedora Core 3).  ES3 uses the older
2.4 kernel, uses SysFS and hotplug rather than udev, SELinux is a rather
bodged-together security system, uses wuftpd rather than vsftpd, uses
XFree86 instead of XOrg and a whole bunch of other things too numerous
to mention.  

CentOS 4.2 and 4.4 use the same base systems, so keeping a 4.2 system
up-to-date gets you much, much closer to a 4.4 system, although they
aren't the same (for example, I believe 4.2 uses an older version of
Gnome than 4.4).  Note also that CentOS 4.2 is equivalent to ES4 Update
2, CentOS 4.4 is equivalent to ES4 Update 4.

Of course, ES5 is now out, and so's CentOS 5--both based on Fedora Core
5.  Fedora is the "bleeding edge" Red Hat Linux.  We Fedora users are
essentially the lab rats for potential Red Hat Enterprise Linux
releases.  We shook the bugs out of FC5 to the point where it was stable
and solid, Red Hat did additional tweaks and now it has now become ES5.

The current release of Fedora is FC6 with FC7 coming out "real soon
now".  I suspect RHEL (ES/AS)5 Update 1 (and CentOS 5.1) will be based
on FC6 in a year or so, but that's just my opinion.  I don't speak for
Red Hat.

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- Rick Stevens, Principal Engineer             rstevens at internap.com -
- VitalStream, Inc.                       http://www.vitalstream.com -
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