Posts Tagged ‘LVM’

How to extend LVM full partition to bigger size on Linux Virtual machine Guest running in VMware vSphere

Tuesday, September 20th, 2022

lvm-filesystem-extend-on-linux-virtual-machine-vmware-physical-group-volume-group-logical-volume-partitions-picture

Lets say you have to resize a partition that is wrongly made by some kind of automation like ansible or puppet,
because the Linux RHEL family OS template was prepared with a /home (or other partition with some very small size)  on VMware Vsphere Hypervisor hosting the Guest linux VM and the partition got quickly out of space.

To resolve the following question comes for the sysadmin

I. How to extend the LVM parititon that run out of space (without rebooting the VM Guest Linux Host)

II. how to add new disk partition space to the vSphere hypervisor OS. 

In below article i'll shortly describe that trivials steps to take to achieve that. Article won't show anything new original but I wrote it,
because I want it to have it logged for myself in case I need to LVM extend the space of my own Virtual machines and 
cause hopefully that might be of help to someone else from the Linux community that has to complete the same task.
 

I . Extending a LVM parititon that run out of space on a Linux Guest VM
 
1. Check the current parititon size that you want to extend

[root@linux-hostname home]# df -h /home/
 Filesystem            Size  Used Avail Use% Mounted on
 /dev/mapper/vg00-home
                       4.7G  4.5G     0 100% /home

2. Check the Virtualization platform

[root@vm-hostname ~]# lshw |head -3
linux-hostname
    description: Computer
    product: VMware Virtual Platform

3. Check the Operating System Linux OS type and version 

In this specific case this is a bit old Redhat -like CentOS 6.9 Linux
 

[root@vmware-host ~]# cat /etc/*release*
CentOS release 6.9 (Final)
CentOS release 6.9 (Final)
CentOS release 6.9 (Final)
cpe:/o:centos:linux:6:GA

4. Find out the type of target filesystem is EXT3, EXT4 or XFS etc.?

[root@vm-hostname ~]# grep home /proc/mounts
/dev/mapper/vg00-home /home ext3 rw,relatime,errors=continue,user_xattr,acl,barrier=1,data=ordered 0 0


Filesystem is handled by LVM thus

5. Check the size of the LVM partition we want to exchange

[root@vm-hostname ~]# lvs |grep home
home vg00 -wi-ao—- 5.00g

6. Check whether free space is available space in the volume group ?

[root@vm-hostname ~]# vgdisplay vg00
  — Volume group —
  VG Name               vg00
  System ID
  Format                lvm2
  Metadata Areas        2
  Metadata Sequence No  15
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                10
  Open LV               10
  Max PV                0
  Cur PV                2
  Act PV                2
  VG Size               128.99 GiB
  PE Size               4.00 MiB
  Total PE              33022
  Alloc PE / Size       30976 / 121.00 GiB
  Free  PE / Size       2046 / 7.99 GiB
  VG UUID               1F89PB-nIP2-7Hgu-zEVR-5H0R-7GdB-Lfj7t4


Extend VMWare space configured for additional hard disk on Hypervisor (if necessery)

In order for to extend the LVM of course you need to have a pre-existing additional hard-drive on VM (sdb,sdc etc. attached )

– If you need to extend on Vmware Vsphere Hypervisor:
Extend additional harddrive by entering the new size and Validate.

If you have previously extended the size of the Virtual Disk from VMWare to make the Linux guest vm find out about the change
you have to rerun rescan for the respective device that was grown on the HV.

7. Rescan on Linux VM host for changes in disk size from Hypervisor

Rescan disk for new size :

[root@vm-hostname ~]# echo 1> /sys/block/sdX/device/rescan

(where sdX is the extended additional harddrive)

8. Resize LVM physical volume

[root@vm-hostname ~]# pvresize /dev/sdX

9. Enlarge Logical Volume size 

[root@vm-hostname ~]# lvextend -L+5G /dev/mapper/vg00-home
     Extending logical volume LogVol00 to 10.77 GiB
     Logical volume LogVol00 successfully resized

10. Enlarge LVM hosted filesystem size

Filesystem is ext3 or ext4 :

[root@vm-hostname ~]# resize2fs /dev/mapper/vg00-home

– If the filesystem is not ext3 / ext4 but XFS you have to use xfs_growfs to let the FS know about the change.

Filesystem is XFS :
 

[root@vm-hostname ~]# xfs_growfs /dev/mapper/vg00-home

11. Check the additional filespace is already active on the Linux Guest VM

[root@vm-hostname ~]# df -h /home/
 Filesystem            Size  Used Avail Use% Mounted on
 /dev/mapper/vg_cloud-LogVol00
                        10G  4.2G  4.9G  48% /home


12. Verify  the extension of filesystem completed without errors


Check of system log:

[root@vm-hostname ~]# grep -i error /var/log/messages
…

Check if filesystem is writable.

[root@vm-hostname ~]# touch /home/test

[root@vm-hostname ~]# ls -al /home/test
-rw-r—– 1 root root 0 Sep 20 13:39 /home/test
[root@vm-hostname ~]# rm -f /home/test


II.  How to add additional sdb drive to a Linux host from vSPhere HV lets say (sdb)


1.  On VSphere GUI  interface

-> Select New hard drive and click Add

Enter the desired size for the new disk then unpack the disk parameters to choose Thin provision. Validate and Apply the recommendations.

basic-lvm-create-volume_group-diagram-on-linux-explained

2. On Linux system VM guest host to detect the new added sdb available space

Discover new disk :

[root@vm-hostname ~]# echo "- – -"> /sys/class/scsi_host/host2/scan && echo "- – -"> /sys/class/scsi_host/host1/scan && echo "- – -"> /sys/class/scsi_host/host0/scan

See  if discovered disk is found in /var/log/messages :

[…]
Nov 8 17:33:26 bict4004s kernel: scsi 2:0:2:0: Direct-Access VMware Virtual disk 1.0 PQ: 0 ANSI: 2
Nov 8 17:33:26 bict4004s kernel: scsi target2:0:2: Beginning Domain Validation
Nov 8 17:33:26 bict4004s kernel: scsi target2:0:2: Domain Validation skipping write tests
Nov 8 17:33:26 bict4004s kernel: scsi target2:0:2: Ending Domain Validation
Nov 8 17:33:26 bict4004s kernel: scsi target2:0:2: FAST-40 WIDE SCSI 80.0 MB/s ST (25 ns, offset 127)
Nov 8 17:33:26 bict4004s kernel: sd 2:0:2:0: Attached scsi generic sg3 type 0
Nov 8 17:33:26 bict4004s kernel: sd 2:0:2:0: [sdb] 2097152 512-byte logical blocks: (1.07 GB/1.00 GiB)
Nov 8 17:33:26 bict4004s kernel: sd 2:0:2:0: [sdb] Write Protect is off
Nov 8 17:33:26 bict4004s kernel: sd 2:0:2:0: [sdb] Cache data unavailable
Nov 8 17:33:26 bict4004s kernel: sd 2:0:2:0: [sdb] Assuming drive cache: write through
Nov 8 17:33:26 bict4004s kernel: sd 2:0:2:0: [sdb] Attached SCSI disk
[…]

3. Create new LVM Physical Volume

[root@vm-hostname ~]# pvcreate /dev/sdb

4. Enlarge LVM Volume Group to the max available size of /dev/sdb

[root@vm-hostname ~]# vgextend vg00 /dev/sdb

Enlarge LVM Logical Volume

[root@vm-hostname ~]# lvextend -L+10G /dev/mapper/vg00-home

5. Enlarge filesystem to max size of just created LVM

If Filesystem is ext3 or ext4 :

[root@vm-hostname ~]# resize2fs /dev/mapper/vg00-home


Again if we work with XFS additionally do:

[root@vm-hostname ~]# xfs_growfs /dev/mapper/vg00-home

6. Checking filesystem extension completed correct

 [root@vm-hostname ~]# df -h /home
…


7. Check filesystem is writtable and no errors produced in logs

Check of system log:

[root@vm-hostname ~]# grep -i error /var/log/messages
…


Check if filesystem is writable.

[root@vm-hostname ~]# touch /home/test
…

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How to mount LVM partition volume on Linux

Wednesday, August 22nd, 2018

lvm-logical-volume-logical-volume-groups

(LVM) = Logical Volume Manager is a device mapper offering logical volume management for the Linux kernel. Virtually all modern GNU / Linux distributions has support for it and using LVM is used among almost all Hosting Providers on (dedicated) backend physical and Virtual XEN / VMWare etc. servers because it provides the ability to merge a number of disks into virtual volumes (for example you have a number of SSD Hard Drives on a server that are under a separate /dev/sda1 /dev/sda2 /dev/sdb3 /dev/sdb4 etc. and you want all the HDDs to appear as a single file system this is managed by Linux LVM.

Logical-volume-manager-linux-explained-diagram.svg

Picture sources Wikipedia

The use of LVM is somewhat similar to RAID 0 disk arrays, where the good about it it allows the removal and addition of hard disks in real time (broken hard disks) on servers to be replaced without service downtime as well as dynamic HDD volume resizal is possible. LVM allows also relatively easy encryption of multiple HDD volumes
with single password.

Discs can be organized in volume groups (so lets say 2 of the server Attached conventional Hard Disks, SCSI or SSDs can be attached to LVM1 and another 3 Hard Drives could be attached to LVM2 group etc.

LVM has been an integral part of Linux kernel since 1998.

lvm is available for install via apt, yum, dhf etc. under a package called lvm2, so to install it on Debian / Ubuntu Fedora Linux (if it is not already installed on the servers with).

 

– Install LVM2 On Debian / Ubuntu
 

debian:~# apt-get install –yes lvm2

 


– Install LVM2 on Fedora / CentOS (Redhat RPM based distros)

 

[root@centos ~]:# yum install -y lvm2


or

[root@fedora ~]:#  dhf install -y lvm2


I. Mounting LVM2 on Linux server after broken DISK change part of a LVM Volume

For example the HDD failed – due to bad sectors and physical HDD head damage damage  – the easiest way to figure that out if the server is running smartd or via a simple HDD test check from BIOS  ( as the ROOT partition is on a LVM it fails to boot properly. You have changed the broken HDD with a brand new and you need to remount the LVM either physically on the server console or remotely via some kind of BIOS KVM interface).

In my experience working for Santrex this was a common sysadmin job, as many of the Virtual Client servers as well as others irons situated in various DataCenters, were occasionally failing to boot and the monitoring system was reporting about the issues and we had to promptly react and bring the servers up.

Here is shortly how we managed to re-mount the LVM after the SSDs / HDDS were substituted:

    1.1. Execute fdisk, vgscan / lvdisplay command

fdisk-lvm-screenshot

lvdisplay-screenshot

vgscan scans all supported LVM block devices in the system for VGs (Virtual Groups)

vgscan-vgchange-screenshot-lvm

    1.2. Next issue vgchange command to activate volume
 

vgchange -ay


   
    1.3. Type lvs command to get information about logical volumes

 

lvs


   
    1.4. Create a mount point using the mkdir command

      That's because we wanted to check the LVM will get properly mounted on next server reboot).
   
     1.5. Mount an LVM volume using
 

server:~# mount /dev/mapper/DEVICE /path/to/mount_point

 

     1.6. To check the size of the LVM (mount points, mounted LVM /dev/names sizes and the amount of free space on each of them use)
 

server:~# df -T

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LVM extend partition Linux howto and how to check if Logical Volume Manager partition is extendable

Thursday, February 13th, 2014

how-to-resize-extend-lvm-partitioned-hard-disks-logical_volume_manager_lvm_logo

Many Linux servers these days are using LVM (Logical Volume Manager) in order to allow disk drives and partitions to be easily managed (shrinked / resized).  It is interesting fact LVM is successor of HP-UX's volume manager. LVM can be considered as a thin software layer on top of the hard disks and partitions, which creates an abstraction of continuity and ease-of-use for managing hard drive replacement, re-partitioning, and backup.

 

LVM is commonly used for the following purposes:

  • Managing large hard disk farms by allowing disks to be added and replaced without downtimes and services disruption (useful whenever hot-swapping is needed)
  • On small systems (like a desktop at home), instead of having to estimate at installation time how big a partition might need to be in the future.
    – LVM lets file systems to be easily resized later as needed.
  • Performing consistent backups by taking snapshots of the logical volumes.
  • Creating single logical volumens of multiple physical volumes or entire hard disks (somewhat similar to RAID-0), ability to do dynamic volume resizing (in LVM partitions are volumes).

So if you're sysadmin it is quite likely that some LVM volume starts being filled up (because of bad initial planning), so the customer asks you to resize a LVM (volume), here is how to do it:

1. Check whether LVM configured on server has free disk space that can be relocated
First lets list all LVM configured volumes on server:

# vgscan
  Reading all physical volumes.  This may take a while...
  Found volume group "web_log" using metadata type lvm2
  Found volume group "web_all" using metadata type lvm2
  Found volume group "rootvg" using metadata type lvm2

vgscan – scan all disks for volume groups and rebuild caches
Then lets display the volume group information.

This is done with vgdisplay cmd
 # vgdisplay
  --- Volume group ---
  VG Name               rootvg
  System ID
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  13
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                11
  Open LV               11
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               136.56 GB
  PE Size               8.00 MB
  Total PE              17480
  Alloc PE / Size       7329 / 57.26 GB
  Free  PE / Size       10151 / 79.30 GB
  VG UUID               27z2w0-Ku0H-y6M0-QFCR-3Rp6-c1HX-OTinzn

[root@lupus ~]# vgs
  VG         #PV #LV #SN Attr   VSize   VFree
  VolGroup00   1   3   0 wz–n- 695.44G    0
[root@lupus ~]# pvs
  PV         VG         Fmt  Attr PSize   PFree
  /dev/sda3  VolGroup00 lvm2 a–  695.44G    0

Important line from above command output is (Free  PE / Size       10151 / 79.30 GB). Indicating that server's LVM had 79.30 GB Free which can be used to extend any of the server LVM existing volumes.

Here are one of servers managed by me existing volumes:

# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/rootvg-root
                      5.0G  301M  4.4G   7% /
udev                   18G  144K   18G   1% /dev
tmpfs                  42G     0   42G   0% /dev/shm
/dev/cciss/c0d0p1     122M   28M   88M  24% /boot
/dev/mapper/rootvg-home
                      512M  268M  219M  56% /home
/dev/mapper/rootvg-opt
                      2.5G  484M  1.9G  21% /opt
/dev/mapper/rootvg-Tivoli
                      3.0G  895M  2.0G  32% /opt/Tivoli
/dev/mapper/rootvg-uc4
                      3.0G  289M  2.6G  11% /opt/uc4
/dev/mapper/rootvg-sysadm
                      3.0G   69M  2.8G   3% /sysadm
/dev/mapper/rootvg-tmp
                      1.3G   35M  1.2G   3% /tmp
/dev/mapper/rootvg-usr
                      4.0G  1.2G  2.6G  32% /usr
/dev/mapper/rootvg-var
                      5.0G  500M  4.2G  11% /var
/dev/mapper/rootvg-webservices
                      9.9G  4.0G  5.9G  41% /webservices
 

For instance lets say the task is to extend LVM (volume) partition:

/dev/mapper/rootvg-webservices
                      9.9G  4.0G  5.9G  41% /webservices

Lets say we want to extend /dev/mapper/rootvg/rootvg-webserices with 20 Gygabytes:
 

# lvextend -L20G /dev/mapper/rootvg-webservices

Then we we would like to add some extra 10GB:

# lvextend -L10G /dev/mapper/rootvg-webservices

In order to add all available LVM free space to a volume use:
 

# lvextend -l +100%FREE /dev/mapper/rootvg-webservices

Whether you had to do it on Linux with kernel 2.4.x and ext2 / ext3 FS:
 

# umount /dev/mapper/rootvg-webservices
# resize2fs /dev/mapper/rootvg-webservices
# mount /dev/mapper/rootvg /webservices

To resize ext4 filesystem with LVM above umount / resize2fs and mount commands can be safely skipped.

On other file systems to raise the size of the filesystem there are different tools to use also on some umount and mount is not necessary example for dynamicly resizable filesystem is reiserfs (though I don't recommend this FS to anyone as the creator of ReiserFS killed his family – moreover my personal experience with ReiserFS in past was quite bitter – I lost personal data because of ReiserFS break ups).

Here is how to dynamicly resize FS after lvextend on Reiserfs filesystem:
 

# resize_reiserfs -f /dev/myvg/homevol

XFS also supports resize of filesystem with no need to re-mount on server with XFS LVM resize after lvextend run:
 

# xfs_growfs /webservices

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How to check /dev/ partition disk labeling in Debian GNU / Linux

Thursday, December 8th, 2011

The usual way that one is supposed to check a certain partition let’s say /dev/sda1 disk UUID (Universal Unique Identifier) label is through a command:
vol_id /dev/sda1

For reason however Debian does not include vol_id command. To check the UUID assigned disk labels on Debian one should use another command called blkid (part of util-linux deb package).

blkid will list all block device attributes so it doesn’t specifically, passing any partition as argument.
Here is an example output of blkid :

server:/root# blkid
/dev/sda1: UUID="cdb1836e-b7a2-4cc7-b666-8d2aa31b2da4" SEC_TYPE="ext2" TYPE="ext3"
/dev/sda5: UUID="c67d6d43-a48f-43ff-9d65-7c707a57dfe6" TYPE="swap"
/dev/sdb1: UUID="e324ec28-cf04-4e2e-8953-b6a8e6482425" TYPE="ext2"
/dev/sdb5: UUID="1DWe0F-Of9d-Sl1J-8pXW-PLpy-Wf9s-SsyZfQ" TYPE="LVM2_member"
/dev/mapper/computer-root: UUID="fbdfc19e-6ec8-4000-af8a-cde62926e395" TYPE="ext3"
/dev/mapper/computer-swap_1: UUID="e69100ab-9ef4-45df-a6aa-886a981e5f26" TYPE="swap"
/dev/mapper/computer-home: UUID="2fe446da-242d-4cca-8b2c-d23c76fa27ec" TYPE="ext3"
 

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