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Interview Preparation : Red Hat Enterprise Linux Administration

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Is it possible to increase the logical volume on fly ?

Answer: Yes.We can increase the logical volume without umount it.

How to reduce the logical volume ? is it possible to reduce on fly ?

Answer: No.You can’t reduce the logical volume on fly. Here is the steps to reduce the logical volume on redhat Linux.
* Un-mount the filesystem
* Run e2fsck on the volume device
* Reduce the Filesystem.(resize2fs)
* Reduce the logical Volume(lvreduce)
* Mount the filesystem back for production.
Thedetailedstep by step guide isavailablehere.

How to do you scan the new LUN or disk for LVM physical volume ?

Answer:Use “pvscan” to scanexistingphysicalvolume from newly connected SAN or DISKS.

How to scan disks forexistingvolume group ?

Answer:Use “vgscan” to scanexistingvolume group from newly connected SAN or DISKS.
But you should use “pvscan” prior to executing this command.

How to scan a logical volume from exising volume group?

Answer: lvscan

How to stop the logical volume ? ordeactivatethe logical volume ?

Answer: “lvchange -an /dev/vg_name/lv_name”

How to activated the logical volume which in deactivated state ?

Answer: “lvchange -ay /dev/vg_name/lv_name” .

How to disable the volume group ? or Deactivate the volume group ?

Answer:”vgchange -an volume_group_name” .

How to enable the volume group ? or Activate the volume group ?

Answer:”vgchange -ay volume_group_name” .

How do you find that what are the disks are used for logical volume mirroring ?

Answer: use “lvs -a -o +devices”

What are steps toperformin order to increase the logical volume on fly ?

Answer:
* Extend the logical volume
* Increase the Filesystem size
* Verify the status using df command or lvs command.

How to list the imported volume groups ?

Answer: Use “vgs” command to display the imported volume group.

How to list the available logical volumes on the system?

Answer: Use “lvs” command to list the available logical volumes on the system.

How to list the available physical volumes in LVM?

Answer: Use “pvs” command to list the available physical volumes.

How to see the detailed volume group information ?

Answer: Use “vgdisplay vg_name”

How to see the detailed logical volume information ?

Answer: Use “lvdisplay /dev/vg_name/lv_name”

How to see the detailed physical volume information ?

Answer: Use “pvdisplay /dev/disk_name” Ex: pvdisplay /dev/sde

How to rename volume Group ? can we rename the VG on fly ?

Answer:Yes.Its possible to rename the volume group on fly.But themountedvolumes will notreflectthe same unless you re-mount the volume with new VG name.
Need to update the /etc/fstab with new VG name to mount the volumes across the system reboot.

How to take a LVM configuration backup ?

Answer:Use “vgcfgbackup vg_name” to take the latest configuration backup of volume group.The default volume group backup location is “/etc/lvm/backup” .

How to re-create the device files for LVM volumes ?

Answer:Run “vgmknodes” to recreate the LVM devices files.
What is lvmdump ?
Answer:“lvmdump” is tool for LVM2 to collect the various information for diagnostic purposes.By default, it creates a tarball suitable for submission along with a problem report

How are snapshots in LVM2 different from LVM1 in Redhat Linux?

Answer:LVM1 snapshots are readonly by default where LVM2 snapshots were read/write.

What are the stepsinvolvedto create the logical volume fromscratch?

Answer:
i.Create a physical volume using pvcreate command.
#pvcreate /dev/sdc
ii.Create a volume group using “vgcreate” command
#vgcreate vg02 /dev/sdc
iii.Create a logical volume using “lvcreate” command
#lvcreate -L 100M -n vol1 vg02
iv.Create a filesystem on logical volume using mkfs command.
#mkfs -t ext4 /dev/vg02/vol1
v.Mount the filesystem using mount command for use.
#mount -t ext4 /dev/vg02/vol1 /vol1

How to extent the volume group ?

Answer:Using “vgextend” we can increase the volume group.
How do you extend the volume group VG02 to , for example, 50GB?
Answer:
1.Get the 50GB lun from SAN team.(/dev/sdd)
2.Create physcical volume ( # pvcreate /dev/sdd )
2.Extend the volume group (# vgextend vg02 /dev/sdd)
If the vg02 has two physical volumes called /dev/sdc/ & /dev/sdd. How do you remove /dev/sdd from vg02.
Answer: “vgreduce vg02 /dev/sdd/”

How todecommission/remove LVMcompletelyfrom the host ?

Answer:
1.Un-mount all the logical filesystems
2.Remove the logical volumes using “lvremove” command.
3.Destroy the volume group using “vgremove” command.
4.Use “pvremove” command remove thephysicalvolumes from the system.

August 13, 2015

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