How can we download a RPM package using YUM? Generally, there are two ways, you can use either yum-downloadonly or yum-utils. 1, yum-downloadonly installation and usage example You just need to install a plugin called yum-downloadonly. This plugin supplies a new parameter called –downloadonly so that yum can download the package s without an further installation/upgrade. It’s much like apt-get‘s -d option in Ubuntu/Debian:

$ yum --help| grep download
Loaded plugins: downloadonly, fastestmirror
  --downloadonly        don't update, just download
  --downloaddir=DLDIR   specifies an alternate directory to store package

A further question is How can I install the download-only plugin for Yum? It’s as simple as a normal install, you just need to run:

$ sudo yum install yum-downloadonly

If you wanna download a package without installation, you just need to add the parameter –downloadonly. By default the downloaded package will be stored in /var/cache/yum, you can specifies an alternate directory to store this file such as /opt, like this:

yum update httpd -y --downloadonly --downloaddir=/opt

2, yum-utils.noarch installation and usage example

Yum-utils is a collection of utilities and plugins extending and supplementing yum in different ways, and all the utilities are contained in yum-utils package, including the one that we need which is called yumdownloader.

# yum -y install yum-utils.noarch

Now we can use the yumdownloader command to download packages from yum repositories. Here’s an example:

# yumdownloader httpd

When you get the RPM, you can query further information from it, or decompress it.

The question is: How can I disable a certain package from being updated by Yum in Linux server environment?

After having a check with the parameter “–help“, I know that the Yum under RedHat / CentOS has an option “–exclude“, and it will exclude a specific package by name or shell glob (* or ?) from being updated, here’re two examples:

1, Bypass updates for an exact package
You can just run this command. Note that you need to login as privileged user to use following commands:

yum --exclude=mysql-server update

2, Bypass some packages with glob
For example, with the following command, you can exclude both mysql-client and mysql-server from update:

yum --exclude=mysql* update

There’s another alternative way to bypass the package.
Yum also supplies a configuration parameter that can be used in /etc/yum.conf to bypass specified packages completely.
To exclude packages from being updated, you can edit /etc/yum.conf and add one line as below:

exclude=mysql*

Further readings: Updating Your System with yum
For any issues, it’s welcome to create postings at our support forum at forum.admon.org!

Before you start, A word of advice i believe most experienced RHEL/CentOS users will show you regarding what you’re thinking:

Upgrade between minor versions (i.e. CentOS 5.2 -> 5.3 -> 5.4, or even 5.0 -> 5.4) YES
Upgrade between major system versions (i.e. CentOS 4.8 to CentOS 5.4) NO

As far as I recall, not even Red Hat recommends this – although they do guarantee the miner updates will go smoothly. Even if you manage to hammer that 4.8 to 5.4 upgrade into place, you might end up with a mess that will be very difficult to maintain. Before processing the system update, it’s suggested to create a backup!

If you are currently running a version of RHEL/CentOS earlier than 4.8 (cat /etc/redhat-release), then please do a proper ‘yum update‘ and get your current system updated to 4.8 before we start.

Then the first thing we need to do is to make sure none of our core binaries, libraries or other content is immutable as it causes package installation failures. If you use immutable bits on system paths then you should run these commands:

chattr -Ria /bin
chattr -Ria /etc
chattr -Ria /etc
chattr -Ria /include
chattr -Ria /lib
chattr -Ria /sbin
chattr -Ria /usr/bin
chattr -Ria /usr/include
chattr -Ria /usr/lib
chattr -Ria /usr/libexec
chattr -Ria /usr/local/bin
chattr -Ria /usr/local/include
chattr -Ria /usr/local/lib
chattr -Ria /usr/local/sbin
chattr -Ria /usr/sbin
chattr -Ria /usr/share
chattr -Ria /var/lib
chattr -Ria /var/lock
chattr -Ria /var/log
chattr -Ria /var/run
chattr -Ria /var/spool/repackage

Once finished, go ahead and have a quick run through of cleaning up yum cache, double check that any pending updates are installed and rebuild the rpmdb:

yum clean all && yum update

If you run into any dependency issues for packages that are not essential, such as syslinux and lftp then you can either exclude them or better just remove them. If the denpency issue is openssh-server related, you can enable telnet login during update by modifing /etc/xinetd.d/telnet.

rpm -e lftp syslinux mkboot

OR (but not recommended)

yum update --exclude=syslinux --exclude=lftp --exclude=mkboot

At this point you should be able to run a ‘yum update‘ command with optional exclude and receive no errors. Now we are ready to get going, please google around, find and download these packages, they mostly available at CentOS official mirror site:

# ls
centos-release-5-4.el5.centos.1.i386.rpm    python-elementtree-1.2.6-5.el4.centos.i386.rpm
centos-release-notes-5.4-4.i386.rpm       python-elementtree-1.2.6-5.el5.i386.rpm
kernel-2.6.18-164.el5.i686.rpm            python-elementtree-1.2.6-5.i386.rpm
kernel-devel-2.6.18-164.el5.i686.rpm      python-sqlite-1.1.7-1.2.1.i386.rpm

We need to go ahead and setup the centos-release package as follows:

rpm -Uhv centos-release-*.rpm

If you see that CentOS-Base.repo was created as /etc/yum.repos.d/CentOS-Base.repo.rpmnew then move it to the right place:

# mv /etc/yum.repos.d/CentOS-Base.repo.rpmnew /etc/yum.repos.d/CentOS-Base.repo

Now we are ready to go with kernel changes, this is an important part so pay attention. The key to successful upgrade is that you remove ALL OLD KERNELS as many packages will fail to install during the upgrade if they detect a release 4.x kernel due to minimum kernel version dependency checks. We will first start with installing the new CentOS 5.4 kernel so it preserves grub templating:

rpm -ivh kernel-2.6.18-164.el5.i686.rpm kernel-devel-2.6.18-164.el5.i686.rpm --nodeps

NOTE: release 5.x has smp support integrated into the standard kernel, so no *-smp version is required for multi-processor systems.

If you are running an older system the chances are you got allot of older kernel packages installed, so make sure you get them all out of the way:

rpm -e $(rpm -qa | grep kernel | grep -v 2.6.18 | tr 'n' ' ') --nodeps

That said and done you should now only have 2 kernel packages installed which are the 2.6.18 release 5.x kernels. DO NOT under any circumstance continue if you still got 2.6.9 release 4.x kernels packages installed, remove them ALL!

# rpm -qa | grep -i kernel
kernel-2.6.18-164.el5
kernel-devel-2.6.18-164.el5

A cleanup of /etc/grub.conf may be required, though the rpm command should have done this for you already, but review it anyways for good measure. You should find that 2.6.18-164.el5 is the only kernel in the file. When kernel updated, a reboot here is OK, but it’s not suggested.

Then we can continute the system updates. There is a known bug with python-elementtree package versions which cause yum/rpm to think the release 4.x version is newer than the 5.x version, to get around this without blowing up the entire python installation we need to remove the package from just the rpmdb as follows:

rpm -e --justdb python-elementtree --nodeps

We can now go ahead and use yum to start the upgrade process, this is a dry run and will take some minutes to compile list of available packages and associated dependency checks. You should carry the exclude options, if any, that you used during the ‘yum update’ process as so to avoid unresolvable dependencies:

yum clean all
yum upgrade

You will end up with a small list of dependency errors, these should be resolved by again evaluating a packages need as a critical system component and either removing it with ‘rpm -e‘ or excluding it with ‘–exclude‘ (remember to query description if you are unsure what something does). In my case the packages that threw up red flags were stuff I had manually installed over time such as nfs in addition to default installed samba, these can all safely be removed or excluded as you prefer.

    Error: Missing Dependency: perl(Convert::ASN1) is needed by package samba
    Error: Missing Dependency: libevent-1.1a.so.1 is needed bypackage nfs-utils

At this point you should be ready to do a final dry run and see where we stand on dependencies, rerun the earlier ‘yum upgrade‘ while making sure to carry over any exclude options you are using.

You should now end up with a summary of actions that yum needs to perform, go ahead and kick it off… this will take a bit time to complete.

    Transaction Summary
    ===========================================================
    Install 183 Package(s)
    Update 527 Package(s)
    Remove 0 Package(s)
    Total download size: 679 M
    Is this ok [y/N]:Y

Once yum has completed we need to fix a few things, the first is the rpmdb needs a rebuild due to version changes that will cause any rpm commands to fail:

rm -f /var/lib/rpm/__db.00*
rpm --rebuilddb
yum clean all

The next issue on the list is python-elementtree and python-sqlite, one or both of these may have ended up in a broken state that will cause all yum commands to break, so we will go ahead and reinstall both of them:

rpm -e --justdb python-elementtree --nodeps
rpm -ivh python-elementtree-1.2.6-5.el5.i386.rpm
rpm -ivh python-sqlite-1.1.7-1.2.1.i386.rpm --nodeps --force

The yum command should now work, go ahead and run it with no options, if you do not get any errors, you are all sorted!

Hopefully the install went well for you, the only thing left to do is go ahead and reboot the system:

shutdown -rf now

For the sake of avoiding a system raised fsck, we will reboot with the -f option to skip fsck.

This is just an announcement email, not the release notes. The Release Notes for CentOS-5.4 can be found on-line at wiki.centos.org.

Download CentOS 5.4 at Mirror.CentOS.org Now!

Since upstream released their 5.4 media, a series of updates have been issued. All these pending updates for CentOS-5.4 will be released over the next 48 to 96 hours to be complete by Monday, 26th Oct 2009.

In some old versioned system, YUM auto-update feature comes as an extension named “yum-autoupdate”, and it contains runlevel scripts and scheduled crontab scripts. 

Enable YUM automatic update

It’s as simple as our services, which can be done as below:

chkconfig --add yum-autoupdate
service yum-autoupdate start

Diable YUM automatic update

Here’s a script for you to do the job, it disables both run-level script, and remove the scheduled cron jobs:

#!/bin/sh
################################
# Disable yum cron and daemons #
################################

echo "++++++++++++++++++++++++++++++++++++++++++++++++"
echo "Yum cron jobs are now disabled"

[ -e /etc/cron.hourly/yum-autoupdate ] && rm -f /etc/cron.hourly/yum-autoupdate
[ -e /etc/cron.hourly/yum ] && rm -f /etc/cron.hourly/yum
[ -e /etc/cron.daily/yum.cron ] && rm -f /etc/cron.daily/yum.cron

yum_status=`chkconfig --list |grep yum |grep "3:on"`
service_name=`chkconfig --list |grep yum | cut -f 1`

for serv in $service_name; do
  if [ "x$yum_status" != "x" ]; then
    echo "++++++++++++++++++++++++++++++++++++++++++++++++"
    echo "+ $serv has been switched to off"
    chkconfig $serv off
  fi

  if [ -e /var/lock/subsys/$serv ]; then
    /etc/init.d/$serv stop
  fi

  echo "Done $serv"
done
############################

If you need to re-enable the service, better to force re-install the extension “yum-autoupdate”, and the removed files will be restored.

[Updates] In recent distributions, the auto-update extension is named yum-updatesd, which has the scheduled cron jobs removed, so basically you can take it as a normal service.

I made a mistake and added additional repo under CentOS / RHEL 5.x server. Now when I try to upgrade packages it gives me out broken ependencies / missing dependency error. How do I skip broken packages and apply updates to other installed software’s?

Packages with broken dependencies is really bad. Yum generally take care of such business, but when you mix additional repos it may give out ‘Missing Dependency’ error under RHEL / CentOS Linux 5.x systems.

You need to add plugin called yum-skip-broken which adds a new parameter --skip-broken to yum to make it possible to check packages for dependency problems and skip the one with problems.

Install yum-skip-broken

Type the following command as root user:

# yum -y install yum-skip-broken

Sample output:

Loading "fastestmirror" plugin
Loading mirror speeds from cached hostfile
* base: mirror.steadfast.net
* updates: mirror.steadfast.net
* addons: centos-distro.cavecreek.net
* extras: mirrors.liquidweb.com
Setting up Install Process
Parsing package install arguments
Resolving Dependencies
--> Running transaction check
---> Package yum-skip-broken.noarch 0:1.1.10-9.el5.centos set to be updated
--> Finished Dependency Resolution
Dependencies Resolved
=======================================================
Package                 Arch       Version          Repository        Size
=======================================================
Installing:
yum-skip-broken         noarch     1.1.10-9.el5.centos  base               11 k
Transaction Summary
======================================================
Install      1 Package(s)
Update       0 Package(s)
Remove       0 Package(s)
Total download size: 11 k
Downloading Packages:
(1/1): yum-skip-broken-1. 100% |=========================|  11 kB    00:00
Running rpm_check_debug
Running Transaction Test
Finished Transaction Test
Transaction Test Succeeded
Running Transaction
Installing: yum-skip-broken              ######################### [1/1]
Installed: yum-skip-broken.noarch 0:1.1.10-9.el5.centos
Complete!

How to handle skiping packages with dependency problems
Now type the command as follows:

# yum -y upgrade --skip-broken

OR

# yum -y update --skip-broken

Finding out that Xen in Redhat Enterprise Linux is not so easy to download – I cannot find it from any public accessible websites, I decided to use CentOS’s yum repoes to download and install Xen. When I have CentOS yum repo created in /etc/yum.repo.d, I noticed that it cannot work in RHEL – It cannot recognize OS version without some updates of application.

That’s why I tried to convert my RHEL 5.3 to CentOS 5.3. Here are the commands that I used. You can just copy & paste:

rpm -e --nodeps redhat-release
rpm -e --nodeps yum-rhn-plugin
wget http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5
rpm --import RPM-GPG-KEY-CentOS-5
rpm -Uvh http://mirror.centos.org/centos/5/os/x86_64/CentOS/centos-release-notes-5.3-3.x86_64.rpm
rpm -Uvh http://mirror.centos.org/centos/5/os/x86_64/CentOS/centos-release-5-3.el5.centos.1.x86_64.rpm
wget http://mirror.centos.org/centos/5/os/x86_64/CentOS/yum-3.2.19-18.el5.centos.noarch.rpm

Now the convertion has finished, you can check /etc/redhat-release for an updated information, and the repo’s config directory for more details on current repoes.

Finally, dont forget to enjoy a FREE CentOS yum updating:

yum clean all
yum update

I’m not quite sure if it totally works well. Nevertheless, I’ve succefully had the system updated, the Xen kernel are running smoothly as well. If I faced any issues, I’d create a new post at our redhat/centos support forum.