VCS Interview Questions In Linux

List of important Veritas Cluster VCS Interview Questions

Following are VCS Interview Questions

Q 1: How to verify the syntax of the main.cf file

Ans: To verify the syntax of the main.cf file just mention the absolute directory path to the main.cf file:  # hacf -verify /etc/VRTSvcs/conf/config

Q 2: How to add a node in an existing cluster?

Ans:    Adding a node into an existing cluster is a multi steps process.

1:       Set up the hardware

Before adding a node to an existing cluster, node must be physically connected with the cluster.

1: Connect the VCS private Ethernet controllers

2: Connect the node to the shared storage

 

2:       Install the VCS software in the node

Install the VCS software and install the license.

 

3:       Configure LLT and GAB

Create the LLT & GAB configuration files (/etc/llthosts, /etc/llttab and /etc/gabtab) in the new node and update the files on the existing node.

 

4:       Add the node to an existing cluster

We have to perform below given tasks in any of the existing node of a cluster

1:Make to cluster configuration R/W

# haconf –makerw

2:Add the new node to the cluster

# hasys –add <new node name>

3:Copy main.cf file from an existing node to new node

# scp /etc/VRTSvcs/conf/config/main.cf new_node:/

/etc/VRTSvcs/conf/config/main.cf

4:Start vcs on the new node

# hastart

5:Now make the configuration again read only.

# haconf –dump –makero

 

 5:       Start VCS and verify the cluster

1:Start VCS on the new node

# hastart

6:       Run the GAB configuration command on each node to verify that port a and port h   include the new node in the membership.

# /sbin/gabconfig -a

Q 3: How to start HAD or VCS ?

Ans: To start HAD or VCS on all nodes in the cluster, the hastart command need to be run on all nodes individually.

# hastart
Q 4: Which is the main config file for VCS and where it is located?
Ans:  main.cf is the main configuration file for VCS and it is located in /etc/VRTSvcs/conf/config.

Q 5: How will you check the status of individual resources of VCS cluster?
Ans:  hares –state
Q 6: How do check the status of VERITAS Cluster Server ?
Ans:  hastatus –sum

Q 7: What is the service group in VCS ?
Ans:  Service group is made up of resources and their links which you normally requires to maintain the HA of application.
Q 8: What are the different resource types ?

Ans:

  1. Persistent : VCS can only monitor these resources but can not offline or online them.
  2. On-Off : VCS can start and stop On-Off resource type. Most resources fall in this category.
  3. On-Only : VCS starts On-Only resources but does not stop them. An example would be NFS daemon. VCS can start the NFS daemon if required, but can not take it offline if the associated service group is take offline.

Q 9: What is the use of halink command ?
Ans:  halink is used to link the dependencies of the resources

Q 10: What is the difference between switchover and failover ?
Ans: Switchover is an manual task where as failover is automatic. You can switchover service group from online cluster node to offline cluster node in case of power outage, hardware failure, schedule shutdown and reboot. But the failover will failover the service group to the other node when VCS heartbeat link down, damaged, broken because of some disaster or system hung.
Q 11: How to online the service groups in VCS ?
Ans: hagrp  -offline (service_group)  -sys (system_name)

Q 12: What is jeopardy in vcs ?
Ans: The state in which a node is missing one of the two required heartbeat connections. When a node is running with one heartbeat only (in jeopardy), VCS does not restart the applications on a new node. This action of disabling failover is a safety mechanism that prevents data corruption.

Q 13: What is the use of hagrp command ?
Ans:  hagrp is used for doing administrative actions on service groups like online, offline, switch etc.

Q 14: How to switchover the service group in VCS ?
Ans:  hagrp  -switch (service_group)  -to (system_name)

Q 15: What is split brain in vcs ?
Ans:  A split brain occurs when two independent systems configured in a cluster assume they have exclusive access to resource. this scenario can be caused when all cluster heartbeat links are simultaneously lost.  Each cluster node will then mark the other cluster node as FAULTED. , usually resulting in data corruption.

Q 16: Cluster Log File location
Ans:  /var/VRTSvcs/log/engine_A.log

Q 17: command  to list the list the parameters of a resource
Ans:  hares -display <resource>

Q 18: command to freeze the service group
Ans:  hagrp -freeze <service group>

Q 19: what is freeze in vcs
Ans:  Freeze a service group to prevent it from failing over to another system.

Q 20: Can I run different versions of VCS in the same cluster?
Ans: No, absolutely not! Different versions of VCS, and even different patch levels of VCS, cannot run at the same time in the same cluster. Therefore, when you install VCS patches, you must install them on *all* nodes at the same time!

Q 21: Difference in critical and non-critical  resource
Ans:     1.(NON-critical ) resource fails , service group will not fail over
2.(Critical ) resource fails , service group will fail over

Q 22: Command to clear the faulty resource
Ans: hares -clear (resource-name)  -sys  (faulted-system)
 
Q 23:  what is the command to Starting and stopping LLT
Ans:      lltconfig -c
lltconfig -U
Q 24: Starting and stopping GAB
Ans:    gabconfig -c -n seed_number
gabconfig –U

Q 25: How to check the status of various GAB ports on the cluster nodes

Ans: To check the status of GAB ports on various nodes :

# gabconfig –a

Q 26: Whats the maximum number of LLT links (including high and low priority) can a cluster have ?

Ans: A cluster can have a maximum of 8 LLT links including high and low priority LLT links.

Q 27: command to  Verifying that links are active for LLT
Ans:   lltstat –n

Q 28: How to check the detailed status of LLT links ?

Ans: The command to check detailed LLT status is :

# lltstat -nvv

Q 29: How can I shutdown VCS without shutting down my applications?
Ans:    (1) hastop -all -force  (shuts down VCS on all nodes)
(2) hastop -local -force  (shuts down VCS on the local node only)

Q 30: What’s the difference between Agents and Resources?
Ans:    Agents are VCS processes that control and monitor the Resources. Resources are all those objects in your  Service Group, and they all require Agents

Q 31: how to Change configuration to read/write mode
Ans: haconf –makerw

Q 32:  command to check vcs licence
Ans: vxlicense –p

Q 33: How to shutdown a node in VCS cluster?

Ans:   Shutting down a VCS node is multi step process.

1) Make the cluster configuration Read/Write

# haconf –makerw

 

2) Either Switchover or failover all the service group which are online on shutting down node to remaining node

# hagrp –switch <service group> -to <node name>

 

3) Freeze all the service group which are online in the cluster.

# hagrp –freeze <service group> -persistent

 

4) Stop the cluster on the node that is going to be down.

# hastop –local –force

 

5) Rename the VCS startup script

# cd /etc/rc3.d

# mv S99vcs s99vcs

 

6) Now reboot the box.

Once the system will come up after reboot, Follow the below given instructions.

1)  Start the VCS on this node

# hastart –force

2) Make the service group online if they were made offline before the system down.

# hagrp –online <service group> -sys <node name>

3) Unfreeze all the service groups which are frozen.

# hagrp -unfreeze <service group> -persistent

4) Now make the cluster configuration Read-Only

# haconf -dump –makero

5) Now again move back the VCS startup script

# cd /etc/rc3.d

# mv s99vcs S99vcs

 

…..Best Of Luck…..
 
 
 

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