LVM Flashcards
What is LVM?
Logical Volume Manager can partition logical volumes (which are flexible) without needing to close the primary partition (dynamically allocated).
What is a dev mapper?
It’s a directory that maps the logical devices to their physical volumes.
What are the advantages we take from LVM?
No downtime, is flexible, can resize (reduce or extend) volumes using a pool (volume group)
What are the three stages of LVM?
pvcreate (physical volume) -> vgcreate (volume group) -> lvcreate (logical volume)
What does the “vgcreate” command do?
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.
What is the physical extent?
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.
What is a Logical Unit Number?
A storage device that can be mounted as a volume
What does LVS command do?
Summarizes the logical volume
How to create physical volume?
pvcreate <device_name1> <device_name2></device_name2></device_name1>
What is volume group? How to list volume groups?
A volume group is a pool of physical volumes. It can be listed with vgs or vgdisplay
How to create a volume group?
vgcreate <name_of_vg> </pv_to_include1> </pv_to_include2> ...</name_of_vg>
What are the types of logical volume?
Linear, striped, mirrored
How to extend a volume group?
vgextend <name_of_vg> </new_pv_to_include></name_of_vg>
How to extend a logical volume?
lvextend -L/-l [+1G/+100%FREE/+extents] </dev/vg/lv>
How to reduce a logical volume?
lvreduce -L/-l [-1G/-10%/-extents] </dev/vg/lv>
Command to resize the xfs file system?
xfs_growfs <mount-point> or you can use -r when resizing logical volumes</mount-point>
Command to resize an ext4 file system?
resize2fs <file-system> or you can use -r when resizing logical volumes</file-system>
How can we shrink the XFS file system on the logical volume?
Can’t shrink xfs
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?
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.
How to list all Logical Volumes and associated Block devices?
lvdisplay
How to see all the mounted file systems?
mount, df -hT
How to scan LUN recently attached to your machine after booting of your machine?
echo “- - -“ > /sys/class/scsi_host/host0/scan
How to format a disk with xfs file system?
mkfs.xfs /dev/partition
How to mount a logical volume “LV1” on /mount_lv1
mount /dev/vg/LV1 /mount_lv1
Your storage is full, and you added a new disk. What steps would you take before extending the LV?
pvcreate to add additional physical volume, vgextend to add that new physical volume to the usuable pool, and then resize lv with lvextend
What is the difference between -L and -l in LV extend?
-L uses human readable sizes (G,M,k), whereas -l uses extents or percentages
How to remove all the file system formats from a disk?
wipefs -a /dev/sda
How to list the mounted file systems? Any two commands
mount or df -hT
What file would you make an entry to make mount point boot persistent?
/etc/fstab
