Introduction to HA and HP Unix Service guard cluster

What is HP UX cluster?

A Serviceguard cluster is a networked grouping of HP 9000 or HP Integrity servers (or both), known as nodes, having sufficient redundancy of software and hardware that a single point of failure will not significantly disrupt service. A package groups application services (individual HP-UX processes) together.  Serviceguard has existed since 1990, which HP claims to have been the first high availability solution for UNIX. HP Serviceguard, formerly known as MC/ServiceGuard, is a high-availability cluster software produced by HP that runs on HP-UX and Linux.

High availability (HA) is a component of a technology system that eliminates single points of failure to ensure continuous operations or uptime for an extended period. High availability clusters are groups of servers that support business-critical applications that require minimal downtime and continuous availability.

Here we are going to tell how to check the status of two node cluster and its package-

Suppose we have two node cluster and 3 packages on each node. And our server rebooted accidently, so here few commands are listed for how can check and run cluster services -

To check cluster status -

#cmviewcl

To run cluster service -

#cmruncl

If above command is showing errors, so you need to check cluster status again -

#cmviewcl

If any nodes or packages still in down state then we need to start them manually -

#cmrunnode nodename

If all packages are in halt state, so we need to login individual nodes to run their packages

#cmrunpkg pkgname

To make enable package up automatically after rebooting -

#cmmodepkg pkgname

In case, we need to set our one node on maintenance and we need to run all service with single node.

Then we need to run all packages in one node and need to halt another node. After that we can put another node in maintenance -

To halt  and shift packages to one node -

#cmhaltpkg pkgname

#cmrunpkg pkgname nodename

To halt node

cmhaltnode nodename

After that we can check all packages will be moved and in up state in one node, while another node will be in haltstate-

#cmviewcl

Congratulations, Now you have run the cluster in single node. 

you can also check our page for 

Import/Export volume group map in HP UNIX cluster

https://lalganjrbl.blogspot.com/search/label/Import%2FExport%20volume%20group%20map%20in%20HP%20UNIX%20cluster

 

Root Password reset in RHEL Linux

How to reset password in Redhat Linux?

If You forget root user password of Linux machine. Then you can reset your root account password by using below easy steps. But you have to take down time first then you can process.


Reboot and edit grub2 :-
1. First of all, reboot your server and press any key to stop auto-boot from the kernel. Then press after scroll down to kernel line (Rescue Mode).

2. When you are in edit mode, go to the line starting with linux16 and edit rd.break like shown in below picture.


Note - You can edit also enforcing=0 options enables omitting the time consuming SELinux relabeling process.

3. Then press Ctrl +X  and  this will reboot the system into rescue mode with changed parameters.

Note - Now the file system is mounted in read-only  on /sysroot/.

4.So now you have to remount /sysroot file system in read-write mode and then use chroot to get in chroot jail.

# mount -o remount,rw /sysroot
# chroot /sysroot

5. Now you can change your root account password by using passwd command.

#passwd

6.After that all unlabeled files ( including shadow file ) gets relabeled during booting. Touching the hidden file autorelabel instructs SElinux to relabel the files changed outside of its regular context, like the file /etc/shadow.

# touch /.autorelabel

7. To flush all cache to disk.
# sync

 After that type exit command two times for reboot the system. Then you can login with updated password.