Re: [linux-lvm] mounting a filesystem on LVM2

["Stuart D. Gathman" <stuart@bmsi.com>]

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On Tue, 5 Oct 2010, Tapas Mishra wrote:

> On Tue, Oct 5, 2010 at 11:54 AM, Stuart D. Gathman <stuart@bmsi.com> wrote:
> > 3) an "LV" is a Logical Volume. �An advanced user might want to use an
> > � LV to simulate a disk, putting a partitional table on it. �Usually
> > � this is done by using the LV as a virtual disk for a Virtual Machine,
> > � which then partitions and uses the virtual disk as it pleases.
> > � You could also use fdisk/parted to partition an LV, and kparted to
> > � make the partitions available as separate block devices.
> 
> This is exactly what I am looking at.
> A tool virt-manager (from Red Hat does that)
> how does it do ?
> While installing a guest OS in an LVM I do not have to create a swap I
> just point to the ISO on my server
> and rest is done.
> How is that part taken care of does virt-manager do it or the OS which
> is being installed some thing from that makes sure that when you are
> installing a guest OS in a virtualization environment then in an LVM
> it will do.
> Because I never needed to create partitions within LVM until I am
> doing this setup to clone the LVM on the server to a
> USB backup drive.

1) man kpartx

2) "partitions within LVM" doesn't make sense.  LVM is a software package,
   not a storage device, and it doesn't do partitions.
   You probably mean "partitions within an LV".

Here is an example of using kpartx:

# lvcreate -L1G -n test vg_sdg
# fdisk /dev/vg_sdg/test
...
# sfdisk -l /dev/vg_sdg/test

Disk /dev/vg_sdg/test: 130 cylinders, 255 heads, 63 sectors/track
Units = cylinders of 8225280 bytes, blocks of 1024 bytes, counting from 0

   Device Boot Start     End   #cyls    #blocks   Id  System
   /dev/vg_sdg/test1          0+     99     100-    803218+  83  Linux
   /dev/vg_sdg/test2        100     129      30     240975   82  Linux swap / Solaris
   /dev/vg_sdg/test3          0       -       0          0    0  Empty
   /dev/vg_sdg/test4          0       -       0          0    0  Empty
# kpartx -l /dev/vg_sdg/test
vg_sdg-test1 : 0 1606437 /dev/vg_sdg/test 63
vg_sdg-test2 : 0 481950 /dev/vg_sdg/test 1606500
# kpartx -av /dev/vg_sdg/test
add map vg_sdg-test1 (253:6): 0 1606437 linear /dev/vg_sdg/test 63
add map vg_sdg-test2 (253:7): 0 481950 linear /dev/vg_sdg/test 1606500
# mke2fs /dev/mapper/vg_sdg-test1
mke2fs 1.41.9 (22-Aug-2009)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
50288 inodes, 200804 blocks
10040 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=209715200
7 block groups
32768 blocks per group, 32768 fragments per group
7184 inodes per group
Superblock backups stored on blocks: 
        32768, 98304, 163840

	Writing inode tables: done                            
	Writing superblocks and filesystem accounting information: done

	This filesystem will be automatically checked every 29 mounts or
	180 days, whichever comes first.  Use tune2fs -c or -i to override.
# mount /dev/mapper/vg_sdg-test1 /mnt/tmp
# df
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/dm-1             15481840  12143008   2552400  83% /
tmpfs                   512672       404    512268   1% /dev/shm
/dev/sda1               295561     95222    185079  34% /boot
/dev/dm-0             36124288  31419784   2869688  92% /home
/dev/dm-3             10321208   5969640   3827324  61% /video
/dev/sr1                  6828      6828         0 100% /media/U3 System
/dev/sdb1              7837760   2046560   5791200  27% /media/Cruzer
/dev/mapper/vg_sdg-test1
                        790556       808    749588   1% /mnt/tmp


-- 
	      Stuart D. Gathman <stuart@bmsi.com>
    Business Management Systems Inc.  Phone: 703 591-0911 Fax: 703 591-6154
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