===== Install logical volumes (LVM) =====

==== Prepare and install volumes ====

Prepare a single disk or a disk raid:
  mkfs.ext3 <phsvol>
  lvm
  lvm> pvcreate <physvol>
  lvm> vgcreate <physvol> // or several physical volumes: <physvol1> <physvol2> <physvol3>
  lvm> lvcreate <volgroup> <physical>
  lvm> quit
  mkfs.ext3 /dev/mapper/<volgroup-logvol>
  mount /dev/mapper/<volgroup-logvol> <dir>

Auto-mount during boot:
  vim /etc/fstab
  /dev/mapper/<volgroup-logvol> <dir> ext3 noatime,user_xattr 0 0
  
===== Replace LVM disk to upgrade capacity =====

This example will copy /dev/sde1 mounted on /backup to /dev/sdf1 mounted on /replace and afterwards change mount point, logical volume and volume group names to the source names.

==== Prepare new disk ====

  * fdisk /dev/sdf
  * **n** to create a new partition, select **1** and accept all defaults
  * **w** to write the new partition table and quit
  * mkfs.ext3 /dev/sdf1
  * lvm
  * lvm > pvcreate /dev/sdf1
  * lvm > vgcreate vg_replace /dev/sdf1
  * lvm > vgdisplay vg_replace to check ### of free extents
  * lvm > lvcreate -l### vg_replace (do not use -LxxGB, use size with -l### which is number of extents)
  * lvm > lvrename vg_replace lvol0 lv_replace
  * lvm > vgcfgbackup to backup volume group configurations
  * lvm > exit
  * mkfs -t ext3 /dev/vg_replace/lv_replace
  * mkdir /replace
  * mount /dev/vg_replace/lv_replace /replace


==== Copy content and assign new disk ====

  * rsync -avH  /backup/* /replace/
  * umount /backup
  * umount /replace
  * lvm
  * lvm > lvrename vg_backup/lv_backup lv_backup1
  * lvm > lvchange vg_backup/lv_backup1 -an
  * lvm > vgrename vg_backup vg_backup1
  * lvm > lvchange vg_backup1/lv_backup1 -ay
  * lvm > lvrename vg_replace/lv_replace lv_backup
  * lvm > lvchange vg_replace/lv_backup -an
  * lvm > vgrename vg_replace vg_backup
  * lvm > lvchange vg_backup/lv_backup -ay
  * lvm > exit
  * mount /dev/vg_backup/lv_backup /backup -o noatime,user_xattr

==== Setting up LVM on top of a Linux Software Raid ====

  * prepare the new disks with a partition (see above), do not create the filesystem yet
  * mdadm --create --verbose /dev/md5 --level=1 --raid-devices=2 /dev/sde /dev/sdf
  * watch the progress with cat /proc/mdstat
  * when finished, restart the computer (shutdown -r now)

==== Merge 2 volume groups ====
  - Unmount and remove LV0 and LV1 from VG1 with umount/lvremove
  - Remove VG1 with vgremove
  - Unmount LV0 and LV1 from VG0 with umount
  - Extend VG0 with any available PVs if necessary
  - Mount LV0 and LV1 on VG0 with mount

  lvcreate -l<extents> -n testlv testvg
  mkfs.ext4 /dev/mapper/vg-lv

===== Increase / decrease size of logical volume =====

First, check the status with:
  # pvs
  # vgs
  # lvs

  * [[https://www.rootusers.com/lvm-resize-how-to-decrease-an-lvm-partition/|LVM Resize – How to Decrease an LVM Partition]]
  * [[https://www.rootusers.com/lvm-resize-how-to-increase-an-lvm-partition/|LVM Resize – How to Increase an LVM Partition]]
  * [[http://www.linuxquestions.org/questions/linux-hardware-18/size-in-superblock-is-different-from-the-physical-size-of-the-partition-298175/| Size in superblock is different from the physical size of the partition]]
  * [[https://www.systutorials.com/124416/shrinking-a-ext4-file-system-on-lvm-in-linux/|Shrinking an Ext4 File System on LVM in Linux]]
  * [[https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/5/html/Deployment_Guide/s1-filesystem-ext4-create.html|Creating an ext4 File System]]
  * [[https://www.tecmint.com/extend-and-reduce-lvms-in-linux/|How to Extend/Reduce LVM’s]]

==== Decrease ====
  - sudo umount /srv/media
  - sudo lvresize --resizefs --size -1024GB /dev/vg_data/lv_media

==== Increase ====
  - sudo lvresize --resizefs --size +1024GB /dev/vg_data/lv_home

  * [[https://blog.100tb.com/resize-or-remove-logical-volumes-with-lvm|Resize Or Remove Logical Volumes With LVM]]