[CentOS-virt] CentOS Images on AWS with partitions on /dev/xvda1 are awkwared to resize

Thu Apr 30 03:24:54 UTC 2015
Kelly Prescott <kprescott at coolip.net>

This is not really a problem at all.
when you launch your image for the first time, you can specify a larger / 
volume size and cloud-init-tools will take care of the rest.
This is well documented in the AWS userguides.

-- Kelly Prescott

On Wed, 29 Apr 2015, Nico Kadel-Garcia wrote:

> I'm staring at the free CentOS images on AWS, and seeing that whoever
> set those up elected to use a partition for /dev/xvda1 rather than
> taking advantage of Amazon's tendency to use "/dev/xvda", "/dev/xvdb",
> etc. for each disk and use those directly as a file system.
> The result is that if you elect to allocate a larger base disk image,
> for example allocating 50 Gig to allow local home directories or space
> for "mock" or for bulky logs, and don't spend the time to select and
> allocate new disk images, it's awkward to simply expand the "/"
> partition. And with only 8 Gig allocated in the latest CentOS 6 images
> that I see in AWS, it's possible to get pretty pressed for space
> pretty quickly.
> Now, AWS published guidelines on manipulating partition size, and
> expanding a matching filesystem, but they're very clear to "unmount
> the parition before you touch it!!!" That's a bit difficult to unmount
> with a "/" partition, and they understandably don't have the kind of
> "boot from CD and work from the console" setup I'd normally use for
> that kind of work.
> So: why did the creators of that CentOS AMI elect to use such a small
> / partition? And how dangerous is it, with the system essentially
> idle, to use "parted" to expand the "/dev/xvda1" parition and then use
> "resize2fs" to expand the "/" file system while the system is alive?
> Note that, because I'm a complete weasel, I know at least one way
> around this: add a second disk, copy the OS to *that*, set grub to
> boot from the second disk, reboot from that, paritition the first disk
> as desired, copy the OS back, reset grub to boot from the first disk,
> and pray. I've had good success with the approach in the past, and
> have rebuilt rougly 15,000 Linux systems this way. But the work
> predates CentOS, and I dont't want to go through that again.
> So, has anyone resized "/" successfully and gracefully on AWS CentOS instances?
>                             Nico Kadel-Garcia
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