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I need help on resize two LVM partitions as I'm afraid of loosing data.

I'm using Ubuntu Server 12.04 headless mode.

LVS:

root@server:/# lvs
  LV      VG   Attr   LSize   Origin Snap%  Move Log Copy%  Convert
  home    LVG  -wi-ao  27,94g
  root    LVG  -wi-ao   6,52g
  storage LVG  -wi-ao 504,84g
  swap    LVG  -wi-ao 732,00m

FDISK:

root@server:/# fdisk -l

Disk /dev/sda: 80.0 GB, 80026361856 bytes
255 heads, 63 sectors/track, 9729 cylinders, total 156301488 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 identifier: 0x00067ea1

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048      585727      291840   83  Linux
/dev/sda2          587774   156301311    77856769    5  Extended
/dev/sda5          587776   156301311    77856768   8e  Linux LVM

Disk /dev/sdb: 500.1 GB, 500107862016 bytes
255 heads, 63 sectors/track, 60801 cylinders, total 976773168 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 identifier: 0x0008c066

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048   976771071   488384512   8e  Linux LVM

Disk /dev/mapper/LVG-root: 6996 MB, 6996099072 bytes
255 heads, 63 sectors/track, 850 cylinders, total 13664256 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 identifier: 0x00000000

Disk /dev/mapper/LVG-root doesn't contain a valid partition table

Disk /dev/mapper/LVG-swap: 767 MB, 767557632 bytes
255 heads, 63 sectors/track, 93 cylinders, total 1499136 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 identifier: 0x00000000

Disk /dev/mapper/LVG-swap doesn't contain a valid partition table

Disk /dev/mapper/LVG-home: 30.0 GB, 29997662208 bytes
255 heads, 63 sectors/track, 3647 cylinders, total 58589184 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 identifier: 0x00000000

Disk /dev/mapper/LVG-home doesn't contain a valid partition table

Disk /dev/mapper/LVG-storage: 542.1 GB, 542063460352 bytes
255 heads, 63 sectors/track, 65902 cylinders, total 1058717696 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 identifier: 0x00000000

Disk /dev/mapper/LVG-storage doesn't contain a valid partition table

I want to shrink my /home LV partition and extent my /storage LV partition.

What is the proper method to do this?

Thanks

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up vote 0 down vote accepted

You have to use vgreduce on the home device and vgextend on the storage device. After that youhave to use resize2fs on both to resize the file system, if not, it will no show the changes.

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It's odd that this answer is marked accepted, because I'm afraid it's quite incorrect. vgreduce and vgextend are for operating on Volume Groups, not individual LVs within a VG. See my answer. – FeRD Feb 1 at 4:03

The lvrezize command is used for altering the size of logical volumes, and can be used to "trade" extents among two LVs within the same volume group.

The most important flag to supply when using lvresize on non-empty / active volumes is the -r flag, which, from the man page:

   -r, --resizefs
          Resize  underlying  filesystem  together with the logical volume
          using fsadm(8).

As long as the -r flag is included, lvresize will change the size of the filesystem on the logical volume to fit the new size of the LV (automatically relocating any occupied blocks in the area to be reduced, when shrinking a volume), which will ensure that no data is lost.

The other important flags, for typical use, are the -L and -l flags for specifying the logical volume's target size, or size delta. Again, the man page:

   -l, --extents [+|-]LogicalExtentsNumber[%{VG|LV|PVS|FREE|ORIGIN}]
          Change or set the  logical  volume  size  in  units  of  logical
          extents.   With  the  +  or - sign the value is added to or sub‐
          tracted from the actual size of the logical volume  and  without
          it,  the value is taken as an absolute one.  The total number of
          physical extents affected will be  greater  than  this  if,  for
          example,  the  volume  is  mirrored.   The  number  can  also be
          expressed as a percentage of the total space in the Volume Group
          with  the suffix %VG, relative to the existing size of the Logi‐
          cal Volume with the suffix %LV, as a percentage of the remaining
          free  space  of the PhysicalVolumes on the command line with the
          suffix %PVS, as a percentage of the remaining free space in  the
          Volume  Group  with  the  suffix %FREE, or (for a snapshot) as a
          percentage of the total space in the Origin Logical Volume  with
          the suffix %ORIGIN.  The resulting value is rounded downward for
          the subtraction otherwise it  is  rounded  upward.   N.B.  In  a
          future  release,  when expressed as a percentage with PVS, VG or
          FREE, the number will be treated as an approximate total  number
          of  physical extents to be allocated or freed (including extents
          used by any mirrors, for example).  The code may currently allo‐
          cate or remove more space than you might otherwise expect.

   -L, --size [+|-]LogicalVolumeSize[bBsSkKmMgGtTpPeE]
          Change  or set the logical volume size in units of megabytes.  A
          size suffix of M for megabytes, G  for  gigabytes,  T  for  ter‐
          abytes, P for petabytes or E for exabytes is optional.  With the
          + or - sign the value is added or  subtracted  from  the  actual
          size  of  the logical volume and rounded to the full extent size
          and without it, the value is taken as an absolute one.

Beyond that, -v' provides verbose output,-t` test runs.

So, to shrink /home by ~50GB, and then add that space to /storage, you could use:

# test run
lvresize -t -v -r -L-50G LVG/home

# If all looks good, shrink for real
lvresize -v -r -L-50G LVG/home

# Give it all to /storage
lvresize -v -r -l+100%FREE LVG/storage

All of this can be done with the volumes mounted, in use, and even actively transferring data during the resize operations. LVM will simply work "underneath" the other disk activity to reconfigure the volumes. (At a cost of speed, of course.)

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