LVM

Question 1

What is LVM?

Answer 1

Logical Volume Manager can partition logical volumes (which are flexible) without needing to close the primary partition (dynamically allocated).

Question 2

What is a dev mapper?

Answer 2

It’s a directory that maps the logical devices to their physical volumes.

Question 3

What are the advantages we take from LVM?

Answer 3

No downtime, is flexible, can resize (reduce or extend) volumes using a pool (volume group)

Question 4

What are the three stages of LVM?

Answer 4

pvcreate (physical volume) -> vgcreate (volume group) -> lvcreate (logical volume)

Question 5

What does the “vgcreate” command do?

Answer 5

Creates a new volume group, which is a pool of volumes made up of 4 mib physical extents. The volume group is created from physical volumes and can, in turn, create logical volumes.

Question 6

What is the physical extent?

Answer 6

A physical extent is a small (4 MiB) chunking of data in a volume group. It’s the smallest building block of a logical volume.

Question 7

What is a Logical Unit Number?

Answer 7

A storage device that can be mounted as a volume

Question 8

What does LVS command do?

Answer 8

Summarizes the logical volume

Question 9

How to create physical volume?

Answer 9

pvcreate <device_name1> <device_name2></device_name2></device_name1>

Question 10

What is volume group? How to list volume groups?

Answer 10

A volume group is a pool of physical volumes. It can be listed with vgs or vgdisplay

Question 11

How to create a volume group?

Answer 11

vgcreate <name_of_vg> </pv_to_include1> </pv_to_include2> ...</name_of_vg>

Question 12

What are the types of logical volume?

Answer 12

Linear, striped, mirrored

Question 13

How to extend a volume group?

Answer 13

vgextend <name_of_vg> </new_pv_to_include></name_of_vg>

Question 14

How to extend a logical volume?

Answer 14

lvextend -L/-l [+1G/+100%FREE/+extents] </dev/vg/lv>

Question 15

How to reduce a logical volume?

Answer 15

lvreduce -L/-l [-1G/-10%/-extents] </dev/vg/lv>

Question 16

Command to resize the xfs file system?

Answer 16

xfs_growfs <mount-point> or you can use -r when resizing logical volumes</mount-point>

Question 17

Command to resize an ext4 file system?

Answer 17

resize2fs <file-system> or you can use -r when resizing logical volumes</file-system>

Question 18

How can we shrink the XFS file system on the logical volume?

Answer 18

Can’t shrink xfs

Question 19

You got a system there is a volume group eg VG_1 and it’s not showing up. What command would you use to show it up?

Answer 19

vgscan scans all SCSI, (E)IDE disks, multiple devices and a bunch of other disk devices in the system looking for LVM physical volumes and volume groups.

Question 20

How to list all Logical Volumes and associated Block devices?

Answer 20

lvdisplay

Question 21

How to see all the mounted file systems?

Answer 21

mount, df -hT

Question 22

How to scan LUN recently attached to your machine after booting of your machine?

Answer 22

echo “- - -“ > /sys/class/scsi_host/host0/scan

Question 23

How to format a disk with xfs file system?

Answer 23

mkfs.xfs /dev/partition

Question 24

How to mount a logical volume “LV1” on /mount_lv1

Answer 24

mount /dev/vg/LV1 /mount_lv1

Question 25

Your storage is full, and you added a new disk. What steps would you take before extending the LV?

Answer 25

pvcreate to add additional physical volume, vgextend to add that new physical volume to the usuable pool, and then resize lv with lvextend

Question 26

What is the difference between -L and -l in LV extend?

Answer 26

-L uses human readable sizes (G,M,k), whereas -l uses extents or percentages

Question 27

How to remove all the file system formats from a disk?

Answer 27

wipefs -a /dev/sda

Question 28

How to list the mounted file systems? Any two commands

Answer 28

mount or df -hT

Question 29

What file would you make an entry to make mount point boot persistent?

Answer 29

/etc/fstab