Re: mkfs and mdadm support

[Ezra Zygmuntowicz <ez@engineyard.com>]

On Jun 12, 2009, at 11:23 PM, snacktime wrote:

> One issue I'm running into is how to handle potentially dangerous  
> operations like mkfs.    mkfs will fail without a force flag if you  
> try to run it on a device that is already initialized with the same  
> filesystem type, but if you run mkfs.ext3 on an xfs filesystem, it  
> will happily create it without any warning.  I know there are other  
> checks that can be done, but one bad regex and bye bye filesystem.   
> Using lvm or raid helps some because you could probably have a rule  
> that if a device exists, it has a filesystem.  Your recipes for  
> creating filesystems always create the device and filesystem in one  
> operation, or not at all.
>
> Another option would be to have a role just for initializing  
> servers.  You put a server into that role to initialize it, and  
> manually take it out once you know it's initialized correctly.   
> Other roles would not have recipes that run mkfs at all.  'Normal'  
> roles would only do things like assembling/stopping raid arrays,  
> mounting/unmounting filesystems, etc..  If I need to add a volume to  
> an existing raid array or lvm group, I do that manually, add it to  
> my json ball, and it just works.  Next reboot chef has the data it  
> needs to bring everything up correctly.
>
> This is one reason why I'm considering have a completely separate  
> resource/provider for mkfs and friends.  I don't want it anywhere  
> near critical data, and the thought of an automated script checking  
> to see if my filesystem needs to be initialized would keep me up at  
> night.
>
> Chris


	The way I'm working with EBS volumes on ec2 where I want it to format  
the EBS device as ext3 *only* if it is not already formatted and then  
ensure it is properly mounted, I also want to grow the filesystem to  
fill the space in case i booted from a snapshot with a larger volume  
size.

 This works perfectly:

if (`grep /dev/sdz1 /etc/fstab` == "")
  Chef::Log.info("EBS device being configured")

  loop do
    # loop until /dev/sdz1 is attached before we allow execution of  
our recipes to continue
    if File.exists?("/dev/sdz1")
        directory "/data" do
          owner 'root'
          group 'root'
          mode 0755
        end

        bash "format-data-ebs" do
          code "mkfs.ext3 -j -F /dev/sdz1"
          not_if "e2label /dev/sdz1"
        end

        bash "mount-data-ebs" do
          code "mount -t ext3 /dev/sdz1 /data"
        end

        bash "grow-data-ebs" do
          code "resize2fs /dev/sdz1"
        end

        bash "add-data-to-fstab" do
          code "echo '/dev/sdz1 /data ext3 noatime 0 0' >> /etc/fstab"
          not_if "grep /dev/sdz1 /etc/fstab"
        end

      break
    end
    Chef::Log.info("EBS device /dev/sdz1 not available yet...")
    sleep 5
  end
end

	You could easily wrap that up in a more abstract resource or  
definition.

Cheers-

Ezra Zygmuntowicz
ez@engineyard.com