Wednesday, 5 February 2020

Fdisk & LVM partition

 Fdisk & LVM partition for Linux

multipath -ll
  274  la
  275  ls
  276  pwd
  277  fdisk /dev/mapper/mpathe
  278  ls -al
  279  partprobe
  280  ls -al
  281  pwd
  282  pvs
  283  pvcreate /dev/mapper/mpathe1
  284  pvs
  285  vgcreate -s 16M u01 /dev/mapper/mpathe1
  286  pvs
  287  vgdisplay
  288  lvcreate --name u01 --size 499.98G u01
  289  lvs
  290  xfs_mkfile /dev/mapper/u01-u01
  291  mkdir -p /u01
  292  mount /dev/mapper/u01-u01 /u01
  293  xfs_mkfile --help
  294  mkfs.xfs /dev/mapper/u01-u01
  295  mount /dev/mapper/u01-u01 /u01
  296  df -kh
  297  vs
  298  pvs
  299  vgs
  300  df -kh

++++++++++++++++++++++++++


Create and Extend XFS filesystem based on LVM

by · Published · Updated
XFS is a File system which is designed for high performance ,scalability and Capacity point of view. It is generally used where large amount data to be stored / used on the File system. Some of the awesome freeze features of xfs are xfs_freeze, snapshot, xfs_unfreeze. One of the limitation of XFS is that we can not shrink or reduce this file system.
XFS is the default file system on CentOS 7 and RHEL 7. In this post we will discuss how to create and extend xfs file system based on LVM in CentOS 7. I am assuming that a new disk is assigned to Linux box and i am going to perform below steps on CentOS 7.

Step:1 Create a partition using fdisk

In the below example i have created 10GB partition on /dev/sdb and set “8e” as toggle id.

Create and Extend XFS filesystem based on LVM

by · Published · Updated
XFS is a File system which is designed for high performance ,scalability and Capacity point of view. It is generally used where large amount data to be stored / used on the File system. Some of the awesome freeze features of xfs are xfs_freeze, snapshot, xfs_unfreeze. One of the limitation of XFS is that we can not shrink or reduce this file system.
XFS is the default file system on CentOS 7 and RHEL 7. In this post we will discuss how to create and extend xfs file system based on LVM in CentOS 7. I am assuming that a new disk is assigned to Linux box and i am going to perform below steps on CentOS 7.

Step:1 Create a partition using fdisk

In the below example i have created 10GB partition on /dev/sdb and set “8e” as toggle id.
fdisk_partition

Step:2 Create LVM components : pvcreate, vgcreate and lvcreate. 

[root@linuxtechi ~]# pvcreate /dev/sdb1
 Physical volume "/dev/sdb1" successfully created
[root@linuxtechi ~]#

[root@linuxtechi ~]# vgcreate vg_xfs /dev/sdb1
 Volume group "vg_xfs" successfully created
[root@linuxtechi ~]#

[root@linuxtechi ~]# lvcreate -L +6G -n xfs_db vg_xfs
 Logical volume "xfs_db" created
[root@linuxtechi ~]#

Step:3 Create XFS file system on lvm parition “/dev/vg_xfs/xfs_db” 

[root@linuxtechi ~]# mkfs.xfs /dev/vg_xfs/xfs_db
create_xfs_filesystem

Step:4 Mount the xfs file system

Create a directory named as xfs_test under /root and mount it using mount command.
mount_xfs_file_system
For the permanent mounting , use /etc/fstab file.

Step:5 Extend the size of xfs file system

Check the whether free space is available in Volume group (vg_xfs) or not using below command :
[root@linuxtechi ~]# vgs vg_xfs 
 VG #PV #LV #SN Attr VSize VFree
 vg_xfs 1 1 0 wz--n- 10.00g 4.00g
[root@linuxtechi ~]#
So we will extend the file system by 3GB using lvextend command with “-r” option
[root@linuxtechi ~]# lvextend -L +3G /dev/vg_xfs/xfs_db -r
lvextend_xfs
As we can see above that the size of “/dev/vg_xfs/xfs_db” has been extended from 6 GB to 9GB
Note : If xfs is not based on LVM , the use the xfs_growsfs command as shown below :
[root@linuxtechi ~]# xfs_growfs <Mount_Point> -D <Size>
The “-D size” option extend the file system to the specified size (expressed in file system blocks). Without the -D size option, xfs_growfs will extend the file system to the maximum size supported by the device.

Step:2 Create LVM components : pvcreate, vgcreate and lvcreate. 

[root@linuxtechi ~]# pvcreate /dev/sdb1
 Physical volume "/dev/sdb1" successfully created
[root@linuxtechi ~]#

[root@linuxtechi ~]# vgcreate vg_xfs /dev/sdb1
 Volume group "vg_xfs" successfully created
[root@linuxtechi ~]#

[root@linuxtechi ~]# lvcreate -L +6G -n xfs_db vg_xfs
 Logical volume "xfs_db" created
[root@linuxtechi ~]#

Step:3 Create XFS file system on lvm parition “/dev/vg_xfs/xfs_db” 

[root@linuxtechi ~]# mkfs.xfs /dev/vg_xfs/xfs_db
create_xfs_filesystem

Step:4 Mount the xfs file system

Create a directory named as xfs_test under /root and mount it using mount command.
mount_xfs_file_system
For the permanent mounting , use /etc/fstab file.

Step:5 Extend the size of xfs file system

Check the whether free space is available in Volume group (vg_xfs) or not using below command :
[root@linuxtechi ~]# vgs vg_xfs 
 VG #PV #LV #SN Attr VSize VFree
 vg_xfs 1 1 0 wz--n- 10.00g 4.00g
[root@linuxtechi ~]#
So we will extend the file system by 3GB using lvextend command with “-r” option
[root@linuxtechi ~]# lvextend -L +3G /dev/vg_xfs/xfs_db -r
lvextend_xfs
As we can see above that the size of “/dev/vg_xfs/xfs_db” has been extended from 6 GB to 9GB
Note : If xfs is not based on LVM , the use the xfs_growsfs command as shown below :
[root@linuxtechi ~]# xfs_growfs <Mount_Point> -D <Size>
The “-D size” option extend the file system to the specified size (expressed in file system blocks). Without the -D size option, xfs_growfs will extend the file system to the maximum size supported by the device.


1) Moving Extents to Existing Physical Volumes

Use the pvs command to check if the desired physical volume (we plan to remove the “/dev/sdb1” disk in LVM) is used or not. 

# pvs -o+pv_used

PV VG Fmt Attr PSize PFree Used
/dev/sda1 myvg lvm2 a- 75.00G 14.00G 61.00G
/dev/sdb1 myvg lvm2 a- 50.00G 45.00G 5.00G
/dev/sdc1 myvg lvm2 a- 17.15G 12.15G 5.00G

If this is used, check to see if there are enough free extents on the other physics volumes in the volume group.

If so, you can run the pvmove command on the device you want to remove. Extents will be distributed to other devices. 

# pvmove /dev/sdb1

/dev/sdb1: Moved: 2.0%
…
/dev/sdb1: Moved: 79.2%
…
/dev/sdb1: Moved: 100.0%

When the pvmove command is complete. Re-use the pvs command to check whether the physics volume is free or not. 

# pvs -o+pv_used

PV VG Fmt Attr PSize PFree Used
/dev/sda1 myvg lvm2 a- 75.00G 9.00G 66.00G
/dev/sdb1 myvg lvm2 a- 50.00G 50.00G 0
/dev/sdc1 myvg lvm2 a- 17.15G 12.15G 5.00G

If it’s free, use the vgreduce command to remove the physical volume /dev/sdb1 from the volume group. 

# vgreduce myvg /dev/sdb1
Removed "/dev/sdb1" from volume group "myvg"

Finally, run the pvremove command to remove the disk from the LVM configuration. Now, the disk is completely removed from the LVM and can be used for other purposes. 

# pvremove /dev/sdb1
Labels on physical volume "/dev/sdb1" successfully wiped.

2) Moving Extents to a New Disk

If you don’t have enough free extents on the other physics volumes in the volume group. Add new physical volume using the steps below.

Request new LUNs from the storage team. Once this is allocated, run the following commands to discover newly added LUNs or disks in Linux. 

# ls /sys/class/scsi_host
host0
# echo "- - -" > /sys/class/scsi_host/host0/scan
# fdisk -l

Once the disk is detected in the OS, use the pvcreate command to create the physical volume. 

# pvcreate /dev/sdd1
Physical volume "/dev/sdd1" successfully created

Use the following command to add new physical volume /dev/sdd1 to the existing volume group vg01. 

# vgextend vg01 /dev/sdd1
Volume group "vg01" successfully extended

Now, use the pvs command to see the new disk “/dev/sdd1” that you have added. 

# pvs -o+pv_used

PV VG Fmt Attr PSize PFree Used
/dev/sda1 myvg lvm2 a- 75.00G 14.00G 61.00G
/dev/sdb1 myvg lvm2 a- 50.00G 0 50.00G
/dev/sdc1 myvg lvm2 a- 17.15G 12.15G 5.00G
/dev/sdd1 myvg lvm2 a- 60.00G 60.00G 0

Use the pvmove command to move the data from /dev/sdb1 to /dev/sdd1.

# pvmove /dev/sdb1 /dev/sdd1

/dev/sdb1: Moved: 10.0%
…
/dev/sdb1: Moved: 79.7%
…
/dev/sdb1: Moved: 100.0%

After the data is moved to the new disk. Re-use the pvs command to check whether the physics volume is free. 

# pvs -o+pv_used

PV VG Fmt Attr PSize PFree Used
/dev/sda1 myvg lvm2 a- 75.00G 14.00G 61.00G
/dev/sdb1 myvg lvm2 a- 50.00G 50.00G 0
/dev/sdc1 myvg lvm2 a- 17.15G 12.15G 5.00G
/dev/sdd1 myvg lvm2 a- 60.00G 10.00G 50.00G

If it’s free, use the vgreduce command to remove the physical volume /dev/sdb1 from the volume group. 

# vgreduce myvg /dev/sdb1
Removed "/dev/sdb1" from volume group "myvg"

Finally, run the pvremove command to remove the disk from the LVM configuration. Now, the disk is completely removed from the LVM and can be used for other purposes. 

# pvremove /dev/sdb1
Labels on physical volume "/dev/sdb1" successfully wiped.
 

Moving Extents to Existing Physical Volumes

In this example, the logical volume is distributed across four physical volumes in the volume group myvg.
# pvs -o+pv_used PV VG Fmt Attr PSize PFree Used /dev/sda1 myvg lvm2 a- 17.15G 12.15G 5.00G /dev/sdb1 myvg lvm2 a- 17.15G 12.15G 5.00G /dev/sdc1 myvg lvm2 a- 17.15G 12.15G 5.00G /dev/sdd1 myvg lvm2 a- 17.15G 2.15G 15.00G
This examples moves the extents off of /dev/sdb1 so that it can be removed from the volume group.
  1. If there are enough free extents on the other physical volumes in the volume group, you can execute the pvmove command on the device you want to remove with no other options and the extents will be distributed to the other devices. 
    # pvmove /dev/sdb1
  /dev/sdb1: Moved: 2.0%
 ...
  /dev/sdb1: Moved: 79.2%
 ...
  /dev/sdb1: Moved: 100.0%
    After the pvmove command has finished executing, the distribution of extents is as follows: 
    # pvs -o+pv_used
  PV         VG   Fmt  Attr PSize  PFree  Used
  /dev/sda1  myvg lvm2 a-   17.15G  7.15G 10.00G
  /dev/sdb1  myvg lvm2 a-   17.15G 17.15G     0
  /dev/sdc1  myvg lvm2 a-   17.15G 12.15G  5.00G
  /dev/sdd1  myvg lvm2 a-   17.15G  2.15G 15.00G
  2. Use the vgreduce command to remove the physical volume /dev/sdb1 from the volume group. 
    # vgreduce myvg /dev/sdb1
  Removed "/dev/sdb1" from volume group "myvg"
# pvs
  PV         VG   Fmt  Attr PSize  PFree
  /dev/sda1  myvg lvm2 a-   17.15G  7.15G
  /dev/sdb1       lvm2 --   17.15G 17.15G
  /dev/sdc1  myvg lvm2 a-   17.15G 12.15G
  /dev/sdd1  myvg lvm2 a-   17.15G  2.15G
The disk can now be physically removed or allocated to other users.

5.4.2. Moving Extents to a New Disk

In this example, the logical volume is distributed across three physical volumes in the volume group myvg as follows: 
# pvs -o+pv_used
  PV         VG   Fmt  Attr PSize  PFree  Used
  /dev/sda1  myvg lvm2 a-   17.15G  7.15G 10.00G
  /dev/sdb1  myvg lvm2 a-   17.15G 15.15G  2.00G
  /dev/sdc1  myvg lvm2 a-   17.15G 15.15G  2.00G
This example procedure moves the extents of /dev/sdb1 to a new device, /dev/sdd1.
  1. Create a new physical volume from /dev/sdd1. 
    # pvcreate /dev/sdd1
  Physical volume "/dev/sdd1" successfully created
  2. Add the new physical volume /dev/sdd1 to the existing volume group myvg. 
    # vgextend myvg /dev/sdd1
  Volume group "myvg" successfully extended
# pvs -o+pv_used
  PV         VG   Fmt  Attr PSize  PFree  Used
  /dev/sda1   myvg lvm2 a-   17.15G  7.15G 10.00G
  /dev/sdb1   myvg lvm2 a-   17.15G 15.15G  2.00G
  /dev/sdc1   myvg lvm2 a-   17.15G 15.15G  2.00G
  /dev/sdd1   myvg lvm2 a-   17.15G 17.15G     0
  3. Use the pvmove command to move the data from /dev/sdb1 to /dev/sdd1. 
    # pvmove /dev/sdb1 /dev/sdd1
  /dev/sdb1: Moved: 10.0%
...
  /dev/sdb1: Moved: 79.7%
...
  /dev/sdb1: Moved: 100.0%

# pvs -o+pv_used
  PV          VG   Fmt  Attr PSize  PFree  Used
  /dev/sda1   myvg lvm2 a-   17.15G  7.15G 10.00G
  /dev/sdb1   myvg lvm2 a-   17.15G 17.15G     0
  /dev/sdc1   myvg lvm2 a-   17.15G 15.15G  2.00G
  /dev/sdd1   myvg lvm2 a-   17.15G 15.15G  2.00G
  4. After you have moved the data off /dev/sdb1, you can remove it from the volume group. 
    # vgreduce myvg /dev/sdb1
  Removed "/dev/sdb1" from volume group "myvg" 
     
     

    This article will serve solution for below questions :

  5. How to safely remove the disk from LVM
  6. How to remove the disk from VG online
  7. How to copy data from one disk to other at the physical level
  8. How to replace a faulty disk in LVM online
  9. How to move physical extents from one disk to another
  10. How to free up disk from VG to shrink VG size
  11. How to safely reduce VG

We have volume group named vg01 which has 20M logical volume created in it and mounted it on /mydata mount point. Check lsblk output below –

root@kerneltalks # lsblk
NAME         MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
xvda         202:0    0  10G  0 disk
├─xvda1      202:1    0   1M  0 part
└─xvda2      202:2    0  10G  0 part /
xvdf         202:80   0   1G  0 disk
└─vg01-lvol1 253:0    0  20M  0 lvm  /mydata

Now, attach new disk of the same or bigger size of the disk /dev/xvdf. Identify the new disk on the system by using lsblk command again and comparing the output to the previous one.

root@kerneltalks # lsblk
NAME         MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
xvda         202:0    0  10G  0 disk
├─xvda1      202:1    0   1M  0 part
└─xvda2      202:2    0  10G  0 part /
xvdf         202:80   0   1G  0 disk
└─vg01-lvol1 253:0    0  20M  0 lvm  /mydata
xvdg         202:96   0   1G  0 disk

You can see the new disk has been identified as /dev/xvdg. Now, we will add this disk to current VG vg01. This can be done using vgextend command. Obviously, before using it in LVM you need to run pvcreate on it.

root@kerneltalks # pvcreate /dev/xvdg
  Physical volume "/dev/xvdg" successfully created.
root@kerneltalks # vgextend vg01 /dev/xvdg
  Volume group "vg01" successfully extended

Now we have disk to be removed /dev/xvdf and new disk to be added /dev/xvdg in the same volume group vg01. You can verify it using pvs command

root@kerneltalks # pvs
  PV         VG   Fmt  Attr PSize    PFree
  /dev/xvdf  vg01 lvm2 a--  1020.00m 1000.00m
  /dev/xvdg  vg01 lvm2 a--  1020.00m 1020.00m

Observe the above output. Since we created a 20M mount point from disk /dev/xvdf it has 20M less free size. The new disk /dev/xvdg is completely free.

Now, we need to move physical extents from disk xvdf to xvdg. pvmove is the command used to achieve this. You just need to supply a disk name from where you need to move out PE. Command will move PE out of that disk and write them to all available disks in the same volume group. In our case, only one other disk is available to move PE.

root@kerneltalks # pvmove /dev/xvdf
  /dev/xvdf: Moved: 0.00%
  /dev/xvdf: Moved: 100.00%

Move progress is shown periodically. If due to any reason operation interrupted in between then moved PE will remain at destination disks and un-moved PEs will remain on the source disk. The operation can be resumed by issuing the same command again. It will then move the remaining PE out of the source disk.

You can even run it in background with nohup.

root@kerneltalks # pvmove /dev/xvdf 2>error.log >normal.log &amp;
[1] 1639

In the above command, it will run pvmove in the background. It will redirect normal console outputs in normal.log file under the current working directory whereas errors will be redirected and saved in error.log file in the current working directory.

Now if you check pvs output again, you will find all space on disk xvdf is free which means its not been used to store any data in that VG. This ensures you can remove the disk without any issues.

root@kerneltalks # pvs
  PV         VG   Fmt  Attr PSize    PFree
  /dev/xvdf  vg01 lvm2 a--  1020.00m 1020.00m
  /dev/xvdg  vg01 lvm2 a--  1020.00m 1000.00m

Before removing/detaching disk from the server, you need to remove it from LVM. You can do this by reducing VG and opting for that disk out.

root@kerneltalks # vgreduce vg01 /dev/xvdf
  Removed "/dev/xvdf" from volume group "vg01"

Now disk xvdf can be removed/detached from server safely.

Few useful switches of pvmove :

Verbose mode prints more detailed information on the operation. It can be invoked by using -v switch.

root@kerneltalks # pvmove -v /dev/xvdf
    Cluster mirror log daemon is not running.
    Wiping internal VG cache
    Wiping cache of LVM-capable devices
    Archiving volume group "vg01" metadata (seqno 17).
    Creating logical volume pvmove0
    activation/volume_list configuration setting not defined: Checking only host tags for vg01/lvol1.
    Moving 5 extents of logical volume vg01/lvol1.
    activation/volume_list configuration setting not defined: Checking only host tags for vg01/lvol1.
    Creating vg01-pvmove0
    Loading table for vg01-pvmove0 (253:1).
    Loading table for vg01-lvol1 (253:0).
    Suspending vg01-lvol1 (253:0) with device flush
    Resuming vg01-pvmove0 (253:1).
    Resuming vg01-lvol1 (253:0).
    Creating volume group backup "/etc/lvm/backup/vg01" (seqno 18).
    activation/volume_list configuration setting not defined: Checking only host tags for vg01/pvmove0.
    Checking progress before waiting every 15 seconds.
  /dev/xvdf: Moved: 0.00%
  /dev/xvdf: Moved: 100.00%
    Polling finished successfully.

The interval at which command updates the progress can be changed. -i switch followed by a number of seconds can be used to get updates from command on user-defined intervals on progress.

root@kerneltalks # pvmove -i 1 /dev/xvdf
⇠ Previous article 
 
 

In this example, we will be deleting “testlv” from the volume group “datavg”. The LV is mounted on the mount point /data01. 

# df -hP | grep -i data01
/dev/mapper/datavg-testlv  976M  2.6M  907M   1% /data01
# lvs
  LV     VG     Attr       LSize  Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  root   centos -wi-ao---- 17.47g
  swap   centos -wi-ao----  2.00g
  testlv datavg -wi-ao----  1.00g
# 1 root@arch-bill /home/bill # gdisk /dev/sdb                                                                                                                                                                                              :(
GPT fdisk (gdisk) version 0.8.10

Partition table scan:
  MBR: protective
  BSD: not present
  APM: not present
  GPT: present

Found valid GPT with protective MBR; using GPT.

Command (? for help): t
Partition number (1-6): 2
Current type is 'Microsoft basic data'
Hex code or GUID (L to show codes, Enter = 8300): 
Changed type of partition to 'Linux filesystem'

Command (? for help): t
Partition number (1-6): 3
Current type is 'Microsoft basic data'
Hex code or GUID (L to show codes, Enter = 8300): 
Changed type of partition to 'Linux filesystem'

Command (? for help): t
Partition number (1-6): 4
Current type is 'Microsoft basic data'
Hex code or GUID (L to show codes, Enter = 8300): 
Changed type of partition to 'Linux filesystem'

Command (? for help): t
Partition number (1-6): 6
Current type is 'Microsoft basic data'
Hex code or GUID (L to show codes, Enter = 8300): 
Changed type of partition to 'Linux filesystem'

Command (? for help): p
Disk /dev/sdb: 3907029168 sectors, 1.8 TiB
Logical sector size: 512 bytes
Disk identifier (GUID): 0645408C-0374-4357-8663-D2A3512E07BD
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 3907029134
Partitions will be aligned on 2048-sector boundaries
Total free space is 4204653 sectors (2.0 GiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1            2048            6143   2.0 MiB     EF02  
   2            8192         8396799   4.0 GiB     8300  
   3         8398848        41953279   16.0 GiB    8300  
   4        41955328       167786495   60.0 GiB    8300  
   6       167788544      3902834687   1.7 TiB     8300  

Command (? for help): w

Final checks complete. About to write GPT data. THIS WILL OVERWRITE EXISTING
PARTITIONS!!

Do you want to proceed? (Y/N): Y
OK; writing new GUID partition table (GPT) to /dev/sdb.
The operation has completed successfully.
1 root@arch-bill /home/bill # fdisk -l                                                                                                                                                                                                    :(

Disk /dev/sdb: 1.8 TiB, 2000398934016 bytes, 3907029168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: 0645408C-0374-4357-8663-D2A3512E07BD

Device           Start          End   Size Type
/dev/sdb1         2048         6143     2M BIOS boot partition
/dev/sdb2         8192      8396799     4G Linux filesystem
/dev/sdb3      8398848     41953279    16G Linux filesystem
/dev/sdb4     41955328    167786495    60G Linux filesystem
/dev/sdb6    167788544   3902834687   1.8T Linux filesystem


Disk /dev/sdc: 298.1 GiB, 320072933376 bytes, 625142448 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 5607E1F7-1A96-4EF5-A353-29BE91873431

Device           Start          End   Size Type
/dev/sdc1         2048      6293503     3G Linux swap
/dev/sdc2      6295552    618600447   292G Microsoft basic data


Disk /dev/sda: 931.5 GiB, 1000204886016 bytes, 1953525168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: C3E095E9-90D9-4BFA-A97F-5D74E64FC4A4

Device           Start          End   Size Type
/dev/sda1         8192     32776191  15.6G Microsoft basic data
/dev/sda2     32778240   1953509375 915.9G Microsoft basic data
/dev/sda3         2048         6143     2M BIOS boot partition

root@arch-bill /home/bill #

1. Delete the entry of the mount point from the /etc/fstab :

# cat /etc/fstab
...
/dev/mapper/datavg-testlv            /data01              ext4    defaults        0 0
...

2. Unmount the mount point :

# umount /data01

3. Disable lvm :

# lvchange -an /dev/datavg/testlv

4. Delete lvm volume :

# lvremove /dev/datavg/testlv

5. Disable volume group :

# vgchange -an datavg

6. Delete volume group :

# vgremove datavg

7. Delete physical Volumes being used for the volume group “datavg” :

# pvremove /dev/sdb  /dev/sdc
      =============
root volume extended in linux
===============
 

Process summary

The process is straightforward. Attach the new storage to the system. Next, create a new Physical Volume (PV) from that storage. Add the PV to the Volume Group (VG) and then extend the Logical Volume (LV).

Look at the picture below. The red line mark shows the original size of the root mount point. The xvdc disk is the new disk attached to it. Extend the root partition to make it 60G in size.

lsblk command displays volume sizes
Figure 1: Use the lsblk command to display volume information.

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Create a Physical Volume

pvcreate command to create a new physical volume
Use the pvcreate command to designate a disk as a PV.
[root@redhat-sysadmin ~]# pvcreate /dev/xvdc
  Physical volume "/dev/xvdc" successfully created.

When you attach the new storage /dev/xvdc, you need to use the pvcreate command in order for the disk to be initialized and be seen by the Logical Volume Manager (LVM).

[ You might also like: Creating and managing partitions in Linux with parted ]

Identify the Volume Group

Next, you need to identify the Volume Group (VG) to which you are extending the new disk with the vgs command. Mine is called centos, and that's the only VG available currently on my LVM.

vgs command displays volume group information
Figure 3: Use the vgs command to display Volume Group information.

Extend the Volume Group

The vgextend command allows you to add one or more initialized Physical Volumes to an existing VG to extend its size.

As you can see, you want to extend the centos Volume Group.

vgextend command
Figure 4: The vgextend command adds capacity to the VG.

After extending it, type the vgs or vgdisplay commands for a more detailed overview of the VG.

The vgs command shows only the VG in with a few lines.

vgs command displays volume group information
Figure 5: Use the vgs command to display VG information.

The vgdisplay shows all the VGs in the LVM and displays the complete information about them.

vgdisplay command displays volume group information
Figure 6: Use the vgdisplay command to display VG information.

As you can see from the image above, marked with red, you have 10GB free. You can decide to extend all or some amount of storage size to it.

Identify the Logical Volume

The lvs or lvdisplay command shows the Logical Volume associated with a Volume Group. Use the lvs command, and the Logical Volume you're trying to extend is the root, which belongs to the centos VG. As you can see above, you've already extended the VG. Next, extend the Logical Volume.

lvs command displays logical volume information
Figure 7: Use the lvs command to display LV information.

Extend the Logical Volume

Extend the LV with the lvextend command. The lvextend command allows you to extend the size of the Logical Volume from the Volume Group.

lvextend command displays logical volume information
Figure 8: Use the lvextend command to extend the LV.
[root@redhat-sysadmin ~]# lvextend -l +100%FREE /dev/centos/root.

Extend the filesystem

You need to confirm the filesystem type you're using, Red Hat uses the XFS filesystem, but you can check the filesystem with lsblk -f or df -Th.

Resize the filesystem on the Logical Volume after it has been extended to show the changes. Resize the XFS filesystem by using the xfs_growfs command.

xfs_grow command extends the XFS filesystem
Figure 9: Use the xfs_growfs command to grow the filesystem on the newly extended LV.

Finally, verify the size of your extended partition.

df -h command displays storage capacity
Figure 10: Use the df -h command to display storage information.

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