Linux LVM

From PedrosBrainDump

Finding the volumes wanted

Use the command lsblk to find what devices you want to use (if it isn't partitioned yet). 

sdb                         8:16   0  32G  0 disk 
sdc                         8:32   0  32G  0 disk 
sdd                         8:48   0  32G  0 disk 
sde                         8:64   0  32G  0 disk 
sdf                         8:80   0  32G  0 disk

In my case I'll use sdb, sdc, sdd, sde and sdf.

Formating the partition

To format the partitions I'll use the fdisk command, to use it you can do the following: 

fdisk /dev/YOUR-DISK

(e.g.) 

fdisk /dev/sdb

And I'll do the following for each disk.

Create a primary partition

To create a primary partition we can use the letter 'n' select 'p' to primary and everything else can be just enter, enter, enter. 

Command (m for help): n
Partition type
   p   primary (0 primary, 0 extended, 4 free)
   e   extended (container for logical partitions)
Select (default p): 

Using default response p.
Partition number (1-4, default 1): 
First sector (2048-67108863, default 2048): 
Last sector, +/-sectors or +/-size{K,M,G,T,P} (2048-67108863,  default 67108863): 

Created a new partition 1 of type 'Linux' and of size 32 GiB.

Change the partition type to Linux LVM

Now to change the partition type to Linux LVM we click 't' and then list all partitions type with the command L, usually Linux LVM can be configured using 'Linux LVM', '8e' or '44'. In my case I wrote Linux LVM 

Command (m for help): t
Selected partition 1
Hex code or alias (type L to list all): Linux LVM
Changed type of partition 'Linux' to 'Linux LVM'.

Save and exit

To save our work and exit the fdisk we click 'w' and it's done. 

Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.

Now we have the /dev/sdb formated let's just reply the same to all other drives wanted.

This is what looks like formating a disk to be an LVM: 

# fdisk /dev/sdd

Welcome to fdisk (util-linux 2.39.3).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

Device does not contain a recognized partition table.
Created a new DOS (MBR) disklabel with disk identifier 0x51929328.

Command (m for help): n
Partition type
   p   primary (0 primary, 0 extended, 4 free)
   e   extended (container for logical partitions)
Select (default p): p
Partition number (1-4, default 1): 
First sector (2048-67108863, default 2048): 
Last sector, +/-sectors or +/-size{K,M,G,T,P} (2048-67108863, default 67108863): 

Created a new partition 1 of type 'Linux' and of size 32 GiB.

Command (m for help): t
Selected partition 1
Hex code or alias (type L to list all): Linux LVM
Changed type of partition 'Linux' to 'Linux LVM'.

Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.

Creating the PV (Physical volume)

Now we have all partitions created we need to create all PVs, this is just simple, use the command pvcreate and the partition created like that: 

pvcreate /dev/sdb1

Then the output should be like 

Physical volume "/dev/sdb1" successfully created.

We can check using the command pvs, like: 

# pvs
  PV         VG        Fmt  Attr PSize   PFree  
  /dev/sdb1  myvg      lvm2 a--  <32.00g <32.00g
  /dev/sdc1  myvg      lvm2 a--  <32.00g <32.00g
  /dev/sdd1  myvg      lvm2 a--  <32.00g <32.00g
  /dev/sde1  myvg      lvm2 a--  <32.00g <32.00g
  /dev/sdf1  myvg      lvm2 a--  <32.00g <32.00g

Creating the VG (Volume group)

Now that all our PVs is created we can create a volume group with the command vgcreate and pass all our PVs to the VG 

vgcreate VG_NAME pv1 pv2 ...

(e.g.) 

vgcreate myvg /dev/sdb1 /dev/sdc1 /dev/sdd1 /dev/sde1

And we should see a message like that 

Volume group "myvg" successfully created

We can check using the command vgs, like: 

# vgs
  VG        #PV #LV #SN Attr   VSize   VFree  
  myvg        5   0   0 wz--n- 159.98g 159.98g

Adding PVs to the VG

To add a new PV on the VG we can use the command vgextend passing the vg name and the pv wanted, like: 

vgextend VG_NAME pv3

(e.g.) 

vgextend myvg /dev/sdf1

And we should have a response like that: 

Volume group "myvg" successfully extended

Removing PVs from the VG

To remove a pv from a vg we can use the command vgreduce passing the vg name and the pv wanted, like: 

vgreduce myvg pv3

(e.g.) 

vgreduce myvg /dev/sdf1

And we should have a response like that: 

Removed "/dev/sdf1" from volume group "myvg"

Updating changes

After any change run the command partprobe just to update all configurations. Shouldn't get any response from the shell.

Verifying the VG created

To check all informations about our VG we can use the command vgdisplay, like: 

# vgdisplay myvg
  --- Volume group ---
  VG Name               myvg
  System ID             
  Format                lvm2
  Metadata Areas        5
  Metadata Sequence No  5
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                0
  Open LV               0
  Max PV                0
  Cur PV                5
  Act PV                5
  VG Size               159.98 GiB
  PE Size               4.00 MiB
  Total PE              40955
  Alloc PE / Size       0 / 0   
  Free  PE / Size       40955 / 159.98 GiB
  VG UUID               2yqVka-ysy3-9Adj-lc6v-3P0f-8a3w-dDb0IH

Creating the LV

To create the LV we can choose use the size or the PE units.

To create using the PE we can use the command: 

lvcreate -L SIZE -n LV_NAME VG_NAME

(e.g.) 

lvcreate -L 150G -n mylv myvg

And we should have a response like that: 

Logical volume "mylv" created.

We can check using the command lvs, like: 

# lvs
  LV        VG        Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  mylv      myvg      -wi-a----- 150.00g

Adding volume to the lv

First add check if you have volume avail on the vg, if yes you can do in 2 ways percentage or size:

Percentage: 

lvextend -l X%FREE /dev/myvg/mylv

(e.g.) 

lvextend -l 100%FREE /dev/myvg/mylv

That way all the avail volume on the vg will be added to the LV.

Fixed size: 

lvextend -L +NG /dev/myvg/mylv

(e.g.) 

lvextend -L +1G /dev/myvg/mylv

That way the lv will extend in 1G.

Resize

After these changes always run 

resize2fs /dev/myvg/mylv

Than the values will be formatted and the lv will assume the actual total volume.

Formating the LV and mounting on the OS

To create a file system on the LV we can use the command mkfs.ext4 or mkfs.xfs or other types of FS, like 

mkfs.ext4 /dev/VG_NAME/LV_NAME

(e.g.) 

# mkfs.ext4 /dev/myvg/mylv

We should get something like that from the shell: 

mke2fs 1.47.0 (5-Feb-2023)
Discarding device blocks: done                            
Creating filesystem with 39321600 4k blocks and 9830400 inodes
Filesystem UUID: 0d1418be-f4f7-4ea9-a309-245c618c9d5a
Superblock backups stored on blocks: 
	32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, 
	4096000, 7962624, 11239424, 20480000, 23887872

Allocating group tables: done                            
Writing inode tables: done                            
Creating journal (262144 blocks): done
Writing superblocks and filesystem accounting information: done

To mount this FS on the OS we can use the command mount 

mount /dev/VG_NAME/LV_NAME OS_MOUNTING_POINT

(e.g.) 

mount /dev/myvg/mylv /mnt

With the command df -h we can check the mounting points, like that: 

Filesystem                         Size  Used Avail Use% Mounted on
/dev/mapper/nfs-nfs                147G   28K  140G   1% /mnt

Auto mounting the LV on the OS on boot

We can do it in two ways, just write the mount command on the /etc/rc.local and the mount command will be executed on boot (link) or we can use the /etc/fstab to mount on boot (link).

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