How can utilize/use the extended space in system.img ?

Question

Hello Guru's
In Oracle VM , How can utilize/use the extended space in system.img ?
a) Increased the system.img size using the following command:
# dd if=/dev/zero bs=1M count=12960 >> /OVS/running_pool/18_test1/System.img
b) Verified the added size of system.img file at OVS server.
# ls -lh System.img
-rw-r--r-- 1 root root 19G Feb 9 20:58 System.img
c) Started GVM and additional size/memory is not shown ?
# df -m
Filesystem 1M-blocks Used Available Use% Mounted on
/dev/xvda2 3984 2292 1652 59% /
/dev/xvda1 92 12 75 14% /boot
tmpfs 512 0 512 0% /dev/shm
+ Tried working with resizefs , resize2fs , cmd did not work.
(GVM is created using Oracle provided template)
+ am i missing anything ?
Oracle VM Setup Detail:
oracle-logos-4.9.17-7ovs
enterprise-linux-ovs-5-0.17
ovs-release-2.2-0.17
ovs-utils-1.0-33
kernel-ovs-2.6.18-128.2.1.4.9.el5
ovs-agent-2.3-29
Thanks in advance for your help.
Best Regards
Basu

Answer 1

I am not positive what you did is going to work, but it seems like you did the equivalent of imaging a small disk on a bigger disk. In that case, the first thing to do is update the partition table with fdisk. Start with fdisk -l in the vm for general information about the disk. Hopefully, the additional space will show. Then, work with fdisk to use the extra space. The easiest is to add a partition, then a file system on it. It is also possible to expand the last partition (you might have to delete it first), then expand what is on it (may be RAID, LVM, or the file system), layer by layer. As usual with fdisk, you run the risk of thrashing it all, so you may want to practice on a copy first. Obviously, the extra space can only be added to the last partition of the small disk.
If the situation is more complex, you may have to boot a VM with both the small disk and the big disk at the same time. If you boot the VM off of an iso DVD image, you can then shell out, then run fdisk to partition the big disk the way you want, then use dd to copy the partitions you want in the order you want from the small disk. I am pretty sure not all combinations will work, but you get the idea. You can then take the small disk out, and boot off of the big disk.
Come to think of it, you might just be better off with adding more space as a second virtual disk. You would then be free to partition/format it the way you want without messing with the first disk. Linux is so good with disk management, so many options.
As a general statement, though, I like to put some distance between the high level file systems and the low level disk partitions, so I use LVM (Logical Volume Manager).
Best of luck, keep us posted.