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As Linux systems have root file systems on a logical volume, it can be used Logical Volume Management (LVM) to resize the volume. The exercise of logical volume expanding is completed in case of adding an extra disk to a physical system or having a pool of storage in a virtual environment.

  1. Run fdisk or gdisk partition tool. gdisk is used if the partition layout is GPT otherwise fdisk has to be used. gdisk will make your system unbootable if you don't have GPT partition. Both tools work identically when a new partiton is created.

    How to figure out if GPT partition is present in your system? Assiming that sda is device with available space, run gdisk /dev/sda command.

    This screen shows that your partition is GPT.

    $ gdisk /dev/sda
    
    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.
    

    In case of MBR partition your screen is.

    $ gdisk /dev/sda
    
    GPT fdisk (gdisk) version 0.8.10
    
    Partition table scan:
      MBR: MBR only
      BSD: not present
      APM: not present
      GPT: not present
    
    ***************************************************************
    Found invalid GPT and valid MBR; converting MBR to GPT format
    in memory. THIS OPERATION IS POTENTIALLY DESTRUCTIVE! Exit by
    typing 'q' if you don't want to convert your MBR partitions
    to GPT format!
    ***************************************************************
    
  2. Create a new logical volume partition. Enter 8E00 partition code.

    Command (? for help): n
    
    Partition number (6-128, default 6): 
    First sector (31457280-52428766, default = 31457280) or {+-}size{KMGTP}: 
    Last sector (31457280-52428766, default = 52428766) or {+-}size{KMGTP}: 
    Current type is 'Linux filesystem'
    Hex code or GUID (L to show codes, Enter = 8300): 8E00
    Changed type of partition to 'Linux LVM'
    
  3. Apply changes.

    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/sda.
    Warning: The kernel is still using the old partition table.
    The new table will be used at the next reboot.
    The operation has completed successfully.
    
  4. Notify the operation system about changes in the partition tables.

    $ partprobe
    
  5. Validate the new created partition. It can be used either fdisk or gdisk partition tool

    $ fdisk -l /dev/sda
    
    WARNING: fdisk GPT support is currently new, and therefore in an experimental phase. Use at your own discretion.
    
    Disk /dev/sda: 26.8 GB, 26843545600 bytes, 52428800 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
    Disk label type: gpt
    Disk identifier: 71DD2E79-BD1C-4713-9880-22664C87E57B
    
    #         Start          End    Size  Type            Name
    1         2048      2099199      1G  Linux filesyste Linux filesystem
    2      2099200     16777215      7G  Linux LVM       Linux LVM
    3     16777216     20971519      2G  Linux LVM       Linux LVM
    4     20971520     31457279      5G  Linux LVM       Linux LVM
    5           34         2047   1007K  BIOS boot       BIOS boot partition
    6     31457280     52428766     10G  Linux LVM       Linux LVM
    
  6. Find out what logical groups/volumes are available.

    $ lvs
    
      LV   VG     Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
      root centos -wi-ao---- <13.19g
      swap centos -wi-ao---- 820.00m
    
  7. Our intertest is to add space to the root file system. The logical volume path is centos/root. In case of RHEL, it might be rhel/root.

  8. Create a physical volume.

    $ pvcreate /dev/sda6
    
    WARNING: ext4 signature detected on /dev/sda6 at offset 1080. Wipe it? [y/n]: y
    Wiping ext4 signature on /dev/sda6.
    Physical volume "/dev/sda6" successfully created.
    
  9. Extend centos volume group.

    $ vgextend centos /dev/sda6
    
    Volume group "centos" successfully extended
    
  10. Figure out exact free space in PE. The field name is Free PE / Size and the value in the sample is 2559

    $ vgdisplay
    
    --- Volume group ---
    VG Name               centos
    System ID             
    Format                lvm2
    Metadata Areas        4
    Metadata Sequence No  8
    VG Access             read/write
    VG Status             resizable
    MAX LV                0
    Cur LV                2
    Open LV               2
    Max PV                0
    Cur PV                4
    Act PV                4
    VG Size               23.98 GiB
    PE Size               4.00 MiB
    Total PE              6140
    Alloc PE / Size       3581 / <13.99 GiB
    Free  PE / Size       2559 / <10.00 GiB
    VG UUID               ZPaYGz-7hbZ-2H6y-RS9W-x13x-2K81-pXCsA3
    
  11. Extend centos/root logical volume

    $ lvextend -l+2559 centos/root
    
    Size of logical volume centos/root changed from <13.19 GiB (3376 extents) to 23.18 GiB (5935 extents).
    Logical volume centos/root successfully resized.
    
  12. XFS file system may be grown while mounted using the xfs_growfs command.

    $ xfs_growfs /dev/centos/root
    
    meta-data=/dev/mapper/centos-root isize=512    agcount=9, agsize=406016 blks
             =                       sectsz=512   attr=2, projid32bit=1
             =                       crc=1        finobt=0 spinodes=0
    data     =                       bsize=4096   blocks=3457024, imaxpct=25
             =                       sunit=0      swidth=0 blks
    naming   =version 2              bsize=4096   ascii-ci=0 ftype=1
    log      =internal               bsize=4096   blocks=2560, version=2
             =                       sectsz=512   sunit=0 blks, lazy-count=1
    realtime =none                   extsz=4096   blocks=0, rtextents=0
    data blocks changed from 3457024 to 6077440
    

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