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upgrading Redhat to  CentOS 3.3

Posted on 2004-09-20
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Last Modified: 2011-09-20
i want to upgrade my redhat 9 pc to fedora i am cuurebtly downloading the ISO file to my redhat 9 box
what i would like to do is run the iso file from the same redhat pc i am upgrading, can someone please help me to do this

i have never done an upgrade like this before always a fresh install fron CD

i want to upgrade because i have everything setup ok like my firewall, snort, apache, rkhunter

when i upgrade will it keep my directory structure and all my file

do i need to keep my old files in root or will they be over written.










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Question by:jaxxman
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15 Comments
 
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Expert Comment

by:jlevie
ID: 12108246
Before any sort of OS upgrade you really want to do a backup of configuration information and data, just in case something goes "horribly wrong". At the least that will mean critical files from /etc like passwd, shadow httpd.conf, etc., or to be safe the entire /etc directory. you'll also want your webserver's files (typically /var/www) and the user's home directories (/home/*). Depending on what you have installed/enabled there may be other things like DB's and config data in /usr/local that need to be saved.

The preferred way of doing the upgrade is to burn the Fedora ISO's to CD and boot from them.
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Author Comment

by:jaxxman
ID: 12114947
my burner is broke,

Is it not possible to upgrade from the iso file
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Author Comment

by:jaxxman
ID: 12115070
my burner is broke,

Is it not possible to upgrade from the iso file
and for me to back up these directories below should restore all my setting
/etc
/var
/usr/local
/home
/root

if i backup all these, then install CentOS 3.3 and overwrite the new directory with my backup files, then would that resore all my network setting and all my programs. if so its easier than a windows upgrade
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Expert Comment

by:jlevie
ID: 12126014
CentOS is based on a RedHat distribution, but I have no idea if it provides for installation from other than CD. I poked aound the CentOS site and didn't find anything helpful in that regard.

With respect to /etc/ /var so don't want to simply copy the backed up data over the system directories. Config file formats and content evolve with time so the old versions of those files may not be compatible with the new OS. What you need to do is to merge things from the old stuff into the corresponding places on the new system. So it is a little more complex.

I recommend copying everything from each user's home dir (root & /home/*) except the dot files. The new OS will probably have a different version of X/Gnome/KDE and those sorts of things will be re-created at login. Shell init scripts should be copied from /etc/skel into each user's home dir.
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Author Comment

by:jaxxman
ID: 12126092
that looks complex have you done this before and could you give a set of instruction on the best way to go about it

i found this http://www.webhostingtalk.com/showthread.php?threadid=276534

check it out i might try it what do you think, upgrading Redhat to  CentOS 3.3
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jlevie earned 125 total points
ID: 12126383
>  that looks complex have you done this before

Frequently...

> and could you give a set of instruction on the best way to go about it

That's essentially impossible except for a particular RH 9 config to a particular "new OS". It's mostly a matter of lookin at what was installed/running on the old system, determining what config files and data were involved, and understanding the old and new content of config files. Then one edits the new config files while referring to the old and re-creates the old functionality.  In the simple cases, like passwd, shadow, group, & gshadow that's simply a matter of copying user account information from the old to the new.

Even an upgrade/update can't always deal with all of this. Afterwards you have to search the system for any *.rpmnew or *.rpmsave files that the update/upgrade left and manually adjust the config files.

According to that URL it should work...
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Author Comment

by:jaxxman
ID: 12126642
oh my God i am well confussed now, looking at all my conf files then editting them this would take for ever. how do i look at whats installed and running just look at the directories.
etc
/var
/usr/local
/home
/root

surley some of these can be copied straight over
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LVL 40

Expert Comment

by:jlevie
ID: 12126979
It isn't as confusing as it sounds. Consider that case where the RH 9 box is a DNS, Web, & Samba server for a local LAN. In that I should already know that:

The DNS server's config file is  /etc/named.conf and the data files are in /var/named, because I would have had to edit those files to set up DNS.

The Web server's config is in /etc/httpd and the default location for the web content is in /var/www, again because of what I did to set up and maintain the web server.

The Samba config is in /etc/samba.

User accounts are in /etc/passwd, /etc/shadow, /etc/group, and /etc/gshadow.

There could be other servers installed on the system, but if they've never been set up or used it doesn't matter about any config files or data that they had, so that stuff in /etc or /var can be ignored.
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Author Comment

by:jaxxman
ID: 12127801
so why not just copy the full /etc directory just be safe and /var

oh when i have upgraded to centos do you know if the splash screen picture logo changes
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Expert Comment

by:jlevie
ID: 12127902
>  so why not just copy the full /etc directory just be safe and /var

Config file formats and content evolve with time so the old versions of those files in your backup may not be compatible with the new OS. What you need to do is to merge things from the old stuff into the corresponding places on the new system. So it is a little more complex.

> oh when i have upgraded to centos do you know if the splash screen picture logo changes

I have no idea
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Author Comment

by:jaxxman
ID: 12128255
centos is 100% compatible with redhat i have had responce from another expert exchange guy and could do with his input how can i get him to join our conversation the user name this expert uses is Xenmaster do you know them
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Expert Comment

by:jlevie
ID: 12128360
>  centos is 100% compatible with redhat

Well yes, since it is based on RHEL 2.1 source rpms. But that doesn't mean that it uses the same versions of applications that you currently have on RedHat 9. And therein lies the  difficulty in simply copying things from RH 9 to CentOS.
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Author Comment

by:jaxxman
ID: 12128409
ok, so are we just taking about *.conf files only
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LVL 40

Expert Comment

by:jlevie
ID: 12129202
Well, that and data files in some cases. I suppose most folks would consider the passwd file to be a data file rather than a config file. From one release to another the UID/GID of some system accounts may change or different accounts may exist. The format of the file remains the same and it is safe to copy the user account line that have been added to the old system to the new passwd file. When doing an upgrade one wouldn't need to do this edit of course.

Other things that live in /etc will change from release to release, like the init scrips located in /etc/rc.d/init. So again we don't just simply copy everything from one release to another.
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Author Comment

by:jaxxman
ID: 12129250
Oh **** i may mess this up but let have ago anyway,

i plan on using pico, and just the cp and mv command only with no parameter

can you give me any commands to start me off that i should be aware of or any quick shortcut tips
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