Redhat Linux Patching

Redhat Linux Patching 

1. Check if the machine is a physical or VM. and check for System Information
# dmidecode -t system

#dmidecode -s system-product-name
#lspci | grep -i vmware
#dmidecode | less

 #cat /etc/info.server

Example :
For Physical :
System Information
        Manufacturer: HP
        Product Name: ProLiant DL385 G5
For Virtual :
System Information
        Manufacturer: VMware, Inc.
        Product Name: VMware Virtual Platform

2. Take System Backup:

For Virtual machines,We can take a snapshot & revert to it in case required.

For Physical machines, check for the ILO address & Take backup using tools if configured.for e.g. TSM backup client,etc.In some environment you may have script  to do backup of the whole rootvg via LVM snapshot.

3. On day of activity use your monitoring tool to acknowledge alerts.

4. Bring App and DB down on server.
5. Go for a simple reboot to ensure server doesn’t have any prior file system issues.
6. Update the kernel on the machine. It is preferable to go for --install instead of --update option.
7. Do a yum update for security and rest patches to complete the update.
8. Reboot the machine.
9. Once up, confirm the server is updated by uname -a and yum check-update.
10. Put server out of Maintenance mode once confirmed Application/DB is up and running.
11. In case of issue, kindly rollback using yum history (RHEL 6)  for RHEL5.

Useful Commands during server patching

• Pre-Patching

Below Commands can be run at once to take prior configuration backup of important files:

mkdir -p /tmp/patching`date +%y%m%d`

cd /tmp/patching`date +%y%m%d`

df -Ph >df.bkp

uptime | tee uptime_before

cat /etc/fstab >fstab.bkp

pvs >pvs.bkp

vgs >vgs.bkp

lvs >lvs.bkp

uname -r  | tee kernel.bkp

cat /etc/grub.conf >grub.bkp

cat /proc/cpuinfo >cpu.bkp

cat /proc/meminfo >mem.bkp

ifconfig -a >ifconfig.bkp

cat /proc/mdstat >mdstat.bkp

netstat -nr >routingtable_before

ls -lhR /boot >bootdir.bkp

fdisk -l >fdisk.bkp

ps -ef >ps_bkp

chkconfig --list >chkconfig.bkp

service --status-all >services_bkp 

top -b1 -n1 >top_bkp

dmidecode -t system | more

multipath -ll >multipath.bkp

powermt display dev=all >powermt.bkp

cat /etc/grub.conf >grub.pre

ls -lhtr

echo "configuration backup done"

cat /etc/info.server

• Patching

yum list   (see available package)

yum update   (ask for Y or N to update packages)

yum update -y (will directly patch the available packages)

yum update -x kernel (exclude kernel update)

• Post-Patching

cat /etc/fstab >fstab.bkp.post

top -b1 -n1 >top_bkp.post

uname -a 

yum check-update
mount -a

/etc/init.d/PowerPath status

Rollback

RollBack Configuration for RHEL 5

edit /etc/rpm/macros

vi /etc/rpm/macros
and add the following line
%_repackage_all_erasures 1

edit /etc/yum.conf
vi /etc/yum.conf
and add the following line
tsflags=repackage

Enable monthly cleanup of old packages, otherwise use too much space
vi /etc/cron.daily/tmpwatch
and add the following line
/usr/sbin/tmpwatch "$flags" 720 /var/spool/repackage

RollBack Configuration for RHEL 6
It’s built-in.

Perform RollBack for RHEL 5
ROLL back RPM:

If OS updated with in one hour period, use the following command
rpm -Uvh --rollback '1 hour ago'

if yesterday
rpm -Uvh --rollback '1 day ago'

if OS updated on a week ago,
rpm -Uvh --rollback '1 week ago'

if OS updated on a month ago,
rpm -Uvh --rollback '1 month ago'

if OS update on Mar 20th,
rpm -Uvh --rollback 'March 20'

Perform RollBack for RHEL 6
Check update history
yum history
Output
Loaded plugins: fastestmirror, refresh-packagekit
ID     | Login user             | Date and time    | Action(s)      | Altered
-------------------------------------------------------------------------------
47 | root <root>            | 2012-05-27 09:03 | Install        |    4  
46 | root <root>            | 2012-05-27 09:02 | Install        |    2  
…

Check info of a particular update
yum history info 46

To rollback to before update ID 47
yum history rollback 46

Undo an update
yum history undo 46

To repeat an update
yum history repeat 46