[virt-tools-list] How to remove a virtual swap disk in a guest image?

Mon May 12 05:24:13 UTC 2014

On Sun, May 11, 2014 at 07:02:04PM -0500, Peng Yu wrote:
>Hi,
>
>The following blocks are from a guest. I have the block
>mintaka--vg-swap_1 which I want to remove (it was created when the
>guest was first made). Then I want the freed space be allocated to
>mintaka--vg-root (so that it will be expanded to 7.7GB). Does anybody
>know what I should do? (I know that this is not related to the usage
>of virsh, but I'm not sure where I should ask this question as I don't
>quite understand how /dev/mapper works) Thanks.
>

So, from what I see below, you managed to do a swapoff on the swap_1
and you want to just remove it and use the space for root, right?

I'm assuming it's in a virtual machine, but it shouldn't really
matter.  To understand what happens here and "how /dev/mapper works",
see some tutorial on logical volumes, etc.

you can remove the LV (swap_1) from the VG (mintaka-vg) using
'lvremove', then lvresize the root LV (root_1) and of course, resize
the filesystem underneath (/) as well.  For virtual machines, you can
use virt-resize from libguestfs as well, which makes it even easier,
I'd say.

However, I'm not writing all the commands here since I don't remember
perfectly what's the synopsys and whether there were any caveats, nor
am I that familiar with virt-resize (and its friends), however
"resizing an lv" is more than enough to google if you need more
guidance than this mail (and appropriate man pages).

Hope that helps,
Martin

>pengy at saiph:~$ lsblk
>NAME                          MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
>sr0                            11:0    1  1024M  0 rom
>vda                           253:0    0    50G  0 disk
>├─vda1                        253:1    0   243M  0 part /boot
>├─vda2                        253:2    0     1K  0 part
>└─vda5                        253:5    0   7.8G  0 part
>  ├─mintaka--vg-root (dm-0)   252:0    0   3.7G  0 lvm  /
>  └─mintaka--vg-swap_1 (dm-1) 252:1    0     4G  0 lvm
>vdb                           253:16   0   256G  0 disk
>└─vdb1                        253:17   0   256G  0 part [SWAP]
>pengy at saiph:~$ ll /dev/mapper/mintaka--vg-swap_1
>lrwxrwxrwx 1 root root 7 May 11 18:53 /dev/mapper/mintaka--vg-swap_1 -> ../dm-1
>pengy at saiph:~$ df -h
>Filesystem                    Size  Used Avail Use% Mounted on
>/dev/mapper/mintaka--vg-root  3.7G  3.4G   78M  98% /
>none                          4.0K     0  4.0K   0% /sys/fs/cgroup
>udev                          106G   12K  106G   1% /dev
>tmpfs                          22G  392K   22G   1% /run
>none                          5.0M     0  5.0M   0% /run/lock
>none                          106G     0  106G   0% /run/shm
>none                          100M     0  100M   0% /run/user
>/dev/vda1                     236M   88M  136M  40% /boot
>pengy at saiph:~$ swapon -s
>Filename                Type        Size    Used    Priority
>/dev/vdb1                               partition    268435420    0    -1
>pengy at saiph:~$ blkid
>/dev/vda1: UUID="df99ebcd-2dcf-4703-ae7c-0e5ec48cc4ca" TYPE="ext2"
>/dev/vda5: UUID="Uz8Imz-aADL-420e-CWo1-sdrS-Zufj-1UFF5u" TYPE="LVM2_member"
>/dev/vdb1: UUID="730e895a-d3ad-4911-993f-dae39a190271" TYPE="swap"
>/dev/mapper/mintaka--vg-root:
>UUID="4bc04e08-add6-4f92-868f-81dce4560adc" TYPE="ext4"
>/dev/mapper/mintaka--vg-swap_1:
>UUID="302daede-eb31-4db5-ad17-6d048931e86e" TYPE="swap"
>pengy at saiph:~$ sudo fdisk -l
>
>Disk /dev/vda: 53.7 GB, 53687091200 bytes
>16 heads, 63 sectors/track, 104025 cylinders, total 104857600 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: 0x0008a759
>
>   Device Boot      Start         End      Blocks   Id  System
>/dev/vda1   *        2048      499711      248832   83  Linux
>/dev/vda2          501758    16775167     8136705    5  Extended
>/dev/vda5          501760    16775167     8136704   8e  Linux LVM
>
>Disk /dev/vdb: 274.9 GB, 274877906944 bytes
>16 heads, 63 sectors/track, 532610 cylinders, total 536870912 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
>
>   Device Boot      Start         End      Blocks   Id  System
>/dev/vdb1              63   536870911   268435424+  83  Linux
>
>Disk /dev/mapper/mintaka--vg-root: 4005 MB, 4005560320 bytes
>255 heads, 63 sectors/track, 486 cylinders, total 7823360 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/mintaka--vg-root doesn't contain a valid partition table
>
>Disk /dev/mapper/mintaka--vg-swap_1: 4290 MB, 4290772992 bytes
>255 heads, 63 sectors/track, 521 cylinders, total 8380416 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/mintaka--vg-swap_1 doesn't contain a valid partition table
>
>
>--
>Regards,
>Peng
>
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