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Adding More Space to Hard Drives

This guide will help you modify partitions and extend partitions and LVM volumes.

Partitions

It is unusual to need to extend partitions but it can be required especially if you have imaged a volume onto a larger disk or perhaps you are using a VM and need the volume to be bigger.

Partitions require great care because the tools for their manipulation can be very destructive if used improperly. As a general rule, you can only add space on to the end of a partition and not at the beginning. Because of the volatile nature, this method is not supported and it is highly advised that you have a very good backup before proceeding.

Let us assume that you have a VM and this is what your layout looks like:

[root@test1 ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/vg_system-lv_root
                      5.5G  1.6G  3.7G  30% /
tmpfs                 499M     0  499M   0% /dev/shm
/dev/sda1             485M   53M  407M  12% /boot
[root@test1 ~]# fdisk -l

Disk /dev/sda: 8589 MB, 8589934592 bytes
255 heads, 63 sectors/track, 1044 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000876bf

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          64      512000   83  Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2              64        1045     7875584   8e  Linux LVM

I have an 8GB disk on my VM and use tools to make it bigger (i.e. 20GB). However you do it, this document assumes that you have a bigger physical disk now and are seeing your existing partitions as a small footprint.

[root@test1 ~]# fdisk -l

Disk /dev/sda: 21.0 GB, 20971520000 bytes
255 heads, 63 sectors/track, 2549 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000876bf

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          64      512000   83  Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2              64        1045     7875584   8e  Linux LVM

As you can see, it is now bigger and our partition does not fill up the disk. With partitions, we are only able to increase the size of /dev/sda2 on this disk. This is because we can move the end of a partition but not the beginning. On this disk /dev/sda1 ends right where /dev/sda2 begins. If we were to extend /dev/sda1 in anyway, it would overwrite the first blocks of /dev/sda2 and destroy that partition.

Take extra special note of start and end boundary of the partition. In this case, we are going to extend /dev/sda2 to the end of our new 20GB disk. The start block for this partition is 64, the Id type is '8e'. This is crucial to note and remember.

Since we are using this partition, we cannot modify it while in use. Reboot the system in Rescue mode by using the ClearBOX rescue mode or your original install CD. Do not mount the partition when asked. Re-run the 'fdisk -l' command when at the rescue mode command prompt to ensure that the rescue mode sees the disk drive names as expected.

Essentially, we will delete and recreate the partition but this time with a new ending partition location. That is why this is dangerous.

https://clearos.com/dokuwiki2/lib/exe/fetch.php?w=550&tok=3c2f8d&media=documentation:clearos_guides:resize_fdisk_partition.png

fdisk /dev/sda

Type 'p' to print the partition table.

Type 'd' to delete the partition.

Type the number of the last partition (in my case it is 2)

Type 'n' to create the partition again.

Type the number of the last partition (in my case it is 2)

Type the number of the block that starts the partition (MUST BE THE SAME)

Type the last block you wish to use (Enter defaults to the last block)

Type 't' to set the partition type.

Type the partition type you recorded earlier (in my case it is '8e').

Type 'p' to reprint the modified partition table.

Ensure that the information is correct. Type 'w' to write the partition to disk.

Reboot the system and ensure that it comes up. If it does not, you may have to recover from backup.

[root@test1 ~]# fdisk -l

Disk /dev/sda: 21.0 GB, 20971520000 bytes
255 heads, 63 sectors/track, 2549 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000876bf

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          64      512000   83  Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2              64        2549    19961818+  8e  Linux LVM

LVM

Ok, so our partition is bigger but we cannot use it yet. As you can see though, it is available now to the LVM system. To resize, let us look at the physical volume:

[root@test1 ~]# pvdisplay
  --- Physical volume ---
  PV Name               /dev/sda2
  VG Name               vg_system
  PV Size               7.51 GiB / not usable 3.00 MiB
  Allocatable           yes (but full)
  PE Size               4.00 MiB
  Total PE              1922
  Free PE               0
  Allocated PE          1922
  PV UUID               dVU16X-1n4n-CcQZ-2kVk-UXZ0-bxQT-gGFuSs

We can see that it is at our previous 7.51 GB, let's resize it:

[root@test1 ~]# pvresize /dev/sda2
  Physical volume "/dev/sda2" changed
  1 physical volume(s) resized / 0 physical volume(s) not resized

Now let's re-examine:

[root@test1 ~]# pvdisplay
  --- Physical volume ---
  PV Name               /dev/sda2
  VG Name               vg_system
  PV Size               19.04 GiB / not usable 37.50 KiB
  Allocatable           yes 
  PE Size               4.00 MiB
  Total PE              4873
  Free PE               2951
  Allocated PE          1922
  PV UUID               dVU16X-1n4n-CcQZ-2kVk-UXZ0-bxQT-gGFuSs

Ok, now we have our space inside the physical volume of our LVM. At this point, you can either create a new volume group or assign the data to the existing volume group. We are going to assign it to an existing volume group:

[root@test1 ~]# vgs
  VG        #PV #LV #SN Attr   VSize  VFree 
  vg_system   1   2   0 wz--n- 19.04g 11.53g
[root@test1 ~]# lvs
  LV      VG        Attr      LSize Pool Origin Data%  Move Log Cpy%Sync Convert
  lv_root vg_system -wi-ao--- 5.54g                                             
  lv_swap vg_system -wi-ao--- 1.97g   

Now we can increase the size of our 'lv_root' LVM

lvextend -l +100%FREE /dev/mapper/vg_system-lv_root
Extending logical volume lv_root to 17.07 GiB
Logical volume lv_root successfully resized

Now our partition for root is much bigger. Verify this by running 'lvs':

[root@test1 ~]# lvs
  LV      VG        Attr      LSize  Pool Origin Data%  Move Log Cpy%Sync Convert
  lv_root vg_system -wi-ao--- 17.07g                                             
  lv_swap vg_system -wi-ao---  1.97g                                    

Alternately, you can allocate blocks instead of a percentage. This can be used to increase the size of all the LVM devices under management.

Here is an example:

lvextend -l +1024 /dev/mapper/vg_system-lv_swap

EXT2 EXT3 EXT4

Ok, the last step requires telling the EXT4 partition that it is bigger. It will require a reboot once you are done.

resize2fs /dev/mapper/vg_system-lv_root 

It should say something like this:

resize2fs 1.41.12 (17-May-2010)
Filesystem at /dev/mapper/vg_system-lv_root is mounted on /; on-line resizing required
old desc_blocks = 1, new_desc_blocks = 2
Performing an on-line resize of /dev/mapper/vg_system-lv_root to 4473856 (4k) blocks.
The filesystem on /dev/mapper/vg_system-lv_root is now 4473856 blocks long.

Under ClearOS 6, this is all that is needed:

[root@test1 ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/vg_system-lv_root
                       17G  1.6G   15G  10% /
tmpfs                 499M     0  499M   0% /dev/shm
/dev/sda1             485M   53M  407M  12% /boot

On some systems, a reboot is necessary. If you can get away with it, we'd recommend that on 6 as well just to be sure that everything comes up alright.

content/en_us/kb_o_adding_more_space_to_hard_drives.txt · Last modified: 2014/12/23 13:34 (external edit)

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