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05-LVM.md

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LOGICAL VOLUME MANAGER

  • Take me to the Tutorial

  • LVM allows grouping of multiple physical volumes, which are hard disks or partitions into a volume group.

  • Volumegroups can be carve out logical volumes.

    LVM

Working with LVM

  • To make use of LVM, install the package LVM .

    [~]$ apt-get install lvm2

  • Use pvcreate command to create a Physical Volume.

    [~]$ pvcreate /dev/sdb
Physical volume "/dev/sdb" successfully created

  • Use vgcreate command to create a Volume Group.

    [~]$ vgcreate caleston_vg /dev/sdb
Volume group "caleston_vg" successfully created

  • Use pvdisplay command to list all the PVs their names, size and the Volume group it is part of.

    [~]$ pvdisplay
--- Physical volume ---
  PV Name /dev/sdb
  VG Name caleston_vg
  PV Size 20.00 GiB / not usable 3.00 MiB
  Allocatable yes
  PE Size 4.00 MiB
  Total PE 5119
  Free PE 5119
  Allocated PE 0
  PV UUID iDCXIN-En2h-5ilJ-Yjqv-GcsR-gDfV-zaf66E

  • Use vgdisplay to see more details of the VG.

    [~]$ vgdisplay
--- Volume group ---
  VG Name caleston_vg
  System ID
  Format lvm2
  Metadata Areas 1
  Metadata Sequence No 1
  VG Access read/write
  VG Status resizable
  MAX LV 0
  Cur LV 0
  Open LV 0
  Max PV 0
  Cur PV 1
  Act PV 1
  VG Size 20.00 GiB
  PE Size 4.00 MiB
  Total PE 5119
  Alloc PE / Size 0 / 0
  Free PE / Size 5119 / 20.00 GiB
  VG UUID VzmIAn-9cEl5bA-lVtm-wHKX-KQaObR

  • To create the Logical Volumes, you can use lvcreate command

    [~]$ lvcreate –L 1G –n vol1 caleston_vg
Logical volume "vol1" created.

  • To display the Logical Volumes, you can use lvdisplay command

    [~]$ lvdisplay
--- Logical volume ---
  LV Path /dev/caleston_vg/vol1
  LV Name vol1
  VG Name caleston_vg
  LV UUID LueYC3-VWpE31-UaYk-wjIR-FjAOyL
  LV Write Access read/write
  LV Creation host, time master, 2020-03-31 06:26:14
  LV Status available
  # open 0
  LV Size 1.00 GiB
  Current LE 256
  Segments 1
  Allocation inherit
  Read ahead sectors auto
  - currently set to 256
  Block device 252:0

  • To list the volume, you can use lvs command

    [~]$ lvs
 LV VG Attr LSize Pool
 vol1 caleston_vg -wi-a----- 1.00g

  • Now to create an filesystem you can use mkfs command

    [~]$ mkfs.ext4 /dev/caleston_vg/vol1

  • To mount the filesystem use mount command

    [~]$ mount –t ext4 /dev/caleston_vg/vol1 /mnt/vol1

  • Now logical volume is now available for use. Lets resize the filesystem on vol1 while it is mounted. Check the free space available.

    [~]$ vgs
VG #PV #LV #SN Attr VSize VFree
caleston_vg 1 1 0 wz--n- 20.00g 19.00g

    [~]$ lvresize -L +1G -n /dev/caleston_vg/vol1
Logical volume vol1 successfully resized.

    [~]$ df –hP /mnt/vol1
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/caleston_vg-vol1 976M 1.3M 908M 1% /mnt/vol1

  • Now to resize the file system use resize2fs command.

    [~]$ resize2fs /dev/caleston_vg/vol1
resize2fs 1.42.13 (17-May-2015)
Filesystem at /dev/mapper/caleston_vg-vol1 is mounted on
/mnt/vol1; on-line resizing required
old_desc_blocks = 1, new_desc_blocks = 1
The filesystem on //dev/mapper/caleston_vg-vol1 is now 524288
(4k) blocks long.

  • Now run df -hp command to verify the size of the mounted filesystem

    [~]$ df –hP /mnt/vol1
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/caleston_vg-vol1 2.0G 1.6M 1.9G 1% /mnt/vol1

    LVM2

HANDS-ON LABS

  • Lets head over to the hands-on labs of LVM