RHCE-Interview Question || LVM02

Part-02

6. How to reduce the File system size in Linux?

Step1:- unmounts the file system

Step2:- we need to reduce the file system size using "resize2fs"
Step3:-Then reduce the lv0 size using "lvreduce"
#umount –l /dev/VG0/LV0
#resize2fs -f /dev/VG0/LV0  3G
#lvreduce -L 3G /dev/VG0/LV0

7.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/”

8.How to extent the volume group ?
Using “vgextend” we can increase the volume group.

9.Assume Volume group “vg02″ is already exists.How do you extend the volume group with 50GB ? Provide all the steps with commands.
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)

10.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/”

11. How to stop the logical volume? or deactivate the logical volume ?
Answer: “lvchange -an /dev/vg_name/lv_name”

12.How to activated the logical volume which in deactivated state ?
Answer: “lvchange -ay /dev/vg_name/lv_name” .

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

#vgchange -an vg_name

14.How to enable the volume group? or Activate the volume group?
#vgchange -ay vg_name

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

Answer: use “lvs -a -o +devices”

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

It’s possible to rename the volume group on flying mode.But the mounted volumes will not reflect the 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.

17. How to take a LVM configuration backup?

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

18. How to re-create the device files for LVM volumes ?
Run “vgmknodes” to recreate the LVM devices files.

19. What is lvmdump? 
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

 20: – Explain LVM snapshot?

LVM snapshots allow the administrator to create a new block device which presents an exact copy of a logical volume, frozen at some point in time.

21.How are snapshots in LVM2 different from LVM1 in Redhat Linux?
Answer:LVM1 snapshots are  readonly by default where LVM2 snapshots were read/write.