lvm application of centos7

1. Create 5 partitions
    /**
     I * Since there is no free disk space left on the machine, we have to delete swap to make space
       */
    1. Delete swap first swapoff /dev/sdax
    2. Modify the boot hang Load the file /etc     / fstab     Delete     the     swap
      line and     save     it Command to update the partition table 2. PV (physical volume) stage     to check whether there is pv       pvscan to create a     new /dev/sda5-8 four partitions for pv       pvcreate /dev/sda{5,6,7,8}     to view the newly created pv       pvscan     lists the pv information on the system in more detail       pvdisplay 3. VG (volume user group) stage     will create a new partition for /dev/sda{5,6,7,8}
   






   









   


      vgcreate -s 16M jisonvg /dev/sda{5,6,7,8}
  -s followed by the size of PE (physical extension block)
    Check the vg of the machine
      vgscan
    check the pv of the machine again
      pvscan
    list the system in more detail vg information
      vgdisplay
4. LV (logical volume) phase
    Allocate the entire jisonvg to jisonlv
      lvcreate -l 72 -n jisonlv jisonvg
  -L followed by the capacity, which can be M, G, T
  -l followed by the number of PEs
  -n The name of the LV is followed by a
    more detailed listing of the lv information on the system .
      lvdisplay 5.     The file system for formatting jisonlv in the file

system phase is ext3       mkfs -t ext3 /dev/jisonvg/jisonlv     Mount jisonlv to       mkdir on /mnt/lvm /mnt/lvm       mount /dev/jisonvg/jisonlv /mnt/lvm     View mounted jisonlv       df -h







    Test using jisonlv
      cp -r /etc /mnt/lvm
      ll /mnt/lvm/etc

6. Enlarge the capacity of LV and
    use the previously created pv (/dev/sda9) that was not added to jisonlv, and add it to jisonvg
      vgextend jisonvg /dev/sda9
    lists the vg information on the system in detail
      vgdisplay
    adjusts the size of jisonlv lvresize
      -l +18 /dev/jisonvg/jisonlv
    lists the lv information above the system in detail
      lvdisplay
    checks the record of the superblock in the original file system
      dumpe2fs /dev /jisonvg/jisonlv
    Completely expand the LV capacity to the entire file system
      resize2fs /dev/jisonvg/jisonlv
    Check the superblock records in the expanded file system
      dumpe2fs /dev/jisonvg/jisonlv
    Check the expanded file system
      df -h / dev/jisonvg/jisonlv

7. Reduce the capacity of LV
    First unmount /dev/jisonvg/jisonlv
      umount /mnt/lvm
    to check the disk
      e2fsck -f /dev/jisonvg/jisonlv
    Reduce the capacity of the file system
      resize2fs /dev/jisonvg/jisonlv 300M
    View the file system after the reduced capacity
      mount /dev/jisonvg /jisonlv /mnt/lvm
      df -h /mnt/lvm
    Reduce the size of LV
      lvresize -l -18 /dev/jisonvg/jisonlv
    Move unused PEs to /dev/sda6
      pvdisplay
      pvmove /dev/sda6 /dev/sda9
    move /dev/sda6 out of jisonvg
      vgreduce jisonvg /dev/sda6
    delete pv (/dev/sda6) pvremove
      /dev/sda6
     
8.LVM snapshot
    Create a snapshot of /dev/jisonvg/jisonlv /dev/jisonvg/jisonss
      pvcreate /dev /sda6
      vgextend jisonvg /dev/sda6
      vgdisplay
      lvcreate -l 18 -s -n jisonss /dev/jisonvg/jisonlv
      lvdisplay
    mount /dev/jisonvg/jisonss
      mkdir /mnt/snapshot
      mount /dev/jisonvg/jisonss /mnt/snapshot
      df -h
      You will find that the usage and size of the snapshots /dev/jisonvg/jisonss and /dev/jisonvg/jisonlv are exactly the same, but in fact the snapshot area is not so big, the snapshot area only records the moment when the snapshot was created /dev/jisonvg The content of /jisonlv
      After modifying /dev/jisonvg/jisonlv, the content of the snapshot area is still unchanged.
    Use the snapshot area to restore the file system
      umount /mnt/snapshot
      df /mnt/lvm
      rm -rf /mnt/lvm/etc
      cp -r / boot /mnt/lvm
      mount /dev/jisonvg/jisonss /mnt/snapshot
      df -h
      At this time, you will find that the usage and size of /dev/jisonvg/jisonlv and /dev/jisonvg/jisonlv are different, the content in the snapshot is still the original, and the content of /dev/jisonvg/jisonlv is after the modification
      . To restore the content of /dev/jisonvg/jisonlv to the original content, after formatting /dev/jisonvg/jisonlv, copy the content of /dev/jisonvg/jisonss to /dev/jisonvg/jisonlv and
      umount /dev /lvm
      mkfs -t ext3 /dev/jisonvg/jisonlv
      mount /dev/jisonvg/jisonlv /mnt/lvm
      cp -r /mnt/snapshot/* /mnt/lvm
      cd /mnt/lvm
      ls
      should be /dev/jisonvg/ The contents of jisonlv and snapshot /dev/jisonvg/jisonss are consistent again
     
9. Close LVM and restore the disk
    Unmount
    umount for swap /mnt/lvm
    umount /mnt/snapshot
    Process snapshot and original system
    lvremove /dev/jisonvg/jisonss
    lvremove /dev/ jisonvg/jisonlv
    make jisonvg inactive
    vgchange -an jisonvg
    delete jisonvg
    vgremove jisonvg
    delete all pv pvremove
    /dev/sda{5,6,7,8,9}
    change /dev/sda{5,6,7,8,9 } Change the 8e flag of the partition back to 83, recreate the partition and format it as swap
    fdisk /dev/sda
    Use the t parameter to modify the id of the partition /dev/sda{5,6,7,8,9} to 83 and
    delete it with the d parameter The /dev/sda{5,6,7,8,9} partition
    uses the d parameter to delete the logical partition /dev/sda4
    uses the n parameter to create a new partition as /dev/sda2
    uses the w parameter to save the partition operation
    Use the partprobe command Refresh the partition table
    to format /dev/sda2 as swap partition
    mkswap /dev/sda2
    and
    reboot