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This particular instance type mounts two ephemeral drives, in /dev/ and /mnt/. I have to create working directories for one of my services in these paths at startup or the services won't launch. Sometimes the script below works, sometimes it does not. I suspect it's a race between the folder being mounted, and my rc.local script kicking off.

Is there a more reliable place I can create these directories? The last time I booted up, the /mnt/mongodb dir did get created, but the /dev/ one did not. I'm running the 12.04 HVM ubuntu instance from amazon.

Here is my rc.local file:

cd /mnt/
sudo mkdir mongodb
sudo chown -R mongodb mongodb
sudo chgrp -R mongodb mongodb
cd /dev/
sudo mkdir mongodb
sudo chown -R mongodb mongodb
sudo chgrp -R mongodb mongodb
sudo service mongodb start
exit 0
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    What is it that mounts the directories? – terdon Oct 28 '13 at 16:48
  • I'm not sure, because these are ephemeral drives that amazon mounts on launch, I'm sure I can find it, but I'm not sure where to look. – Tom Swifty Oct 28 '13 at 17:06
  • Well, you could just add a test in your rc.local that will only create the directory if the volume is mounted. That will make you system wait until they have been mounted. – terdon Oct 28 '13 at 17:14
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I believe it is the cloud-init package that automatically mounts the first ephemeral disc as /mnt. /dev should be just for devices. So the first ephemeral disc (or instance store) will be exposed as /dev/sdb (or /dev/xvdb) and them mounted as /mnt. If you provide your script as instance user data, i.e. use the cloud-init system, then it will be run after the cloud-init system has created the mount. Alternatively, you need to set its order so it runs after cloud-init. Or you could beat cloud-init to it and create the mount yourself.

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