[WBEL-users] Upgrading from Whitebox to RHEL

[Scott Silva]

Mike B. spake the following on 4/26/2007 7:37 PM:
> At 4/26/2007 01:09 PM, Scott Silva wrote:
> 
>> wasting your money. They will probably recommend a clean install and
>> careful
>> data restore.
> 
> This raises a different question...one that may be obvious to long-time
> unix/linux folks, but not to us relatively new ones:
> 
> What is the best way to deal with upgrades and re-installations of
> linux?  That is, how do you preserve all the configuration changes,
> startup customizations, user accounts, cron scripts, DNS zone files, and
> other system management "stuff" that accumulates on a system over time
> when you re-install the OS or upgrade or switch to a different
> distribution?  Manually re-customizing and repeating all the setup work
> may be possible, but it's not an attractive option at all.
> 
> When you upgrade within a distro this is usually not an issue...files
> don't get deleted, upgrade scripts usually rename them if they get
> replaced with upgraded ones so you can merge in whatever is still
> relevant, and user directories aren't touched, etc..  When you do a
> clean install, this isn't the case.
> 
> Getting listings of files changed since you installed before you shut
> down the old system might be one way to catch what you need to save, but
> it will also catch a lot of stuff you may not care about (old logs,
> backup copies of edited files, programs that are going to be replaced
> anyway, programs you don't want anymore, etc.) and weeding it isn't much
> more attractive than repeating all the work.
> 
> If you were really organized, you'd maintain a copy of all updated
> critical files in some directory that isn't part of the "system"...like
> the sysadmin's home directory tree, or a directory off of /home or
> something, and always change there then copy into /etc, /var or wherever
> the files need to live, but all it would take is a small lapse of
> attention and you'd be missing something potentially important.  If you
> had such a thing, you could pretty easily copy again after making sure
> the file contents were still relevant.
> 
> How do the experienced folks deal with this problem?
> 
> -- Mike B.
Most configuration files are in the /etc directory.  If you install something
that stores its config files somewhere else, make a symlink into /etc for it
so you can just tar the /etc directory occasionally. If you put your /home
directory on a separate filesystem, it can be left untouched during the new OS
install.
When I migrate a server, and I don't have new hardware to install to, I try to
copy everything to a large enough hard drive or two. Then you can install the
new OS and take your time migrating.
If it is a critical server, and you can not afford the down time, You should
really get another piece of hardware. You can get an older server and move to
it so the newer hardware is free for upgrade.

I have done some in place upgrades, but I will usually make a list of all the
installed rpms with rpm -qa |sort >rpmlist.txt before and after the upgrade,
and compare the list with a log from a fresh install in a vmware vm. That way
I can look for orphaned rpms.


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