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I'm crafting up a shell script (to be called by cron) that runs smartctl on the booted disk on a weekly basis. Is there a fairly universal way to determine what the boot block device is (IE - /dev/sda, /dev/hdb, etc)? The expected install would be standard, I think I could get away with using grep " / " on /etc/fstab, I'm just wondering if there's a more graceful way.

This script will specifically be deployed on Fedora and possibly Ubuntu boxes.

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Are you really looking for the boot device, or are you looking for the root device? If you are looking for / in fstab, and your boot device is different from your root device then you may not get the results you want. – Zoredache Dec 8 '11 at 19:13
That is a valid point. For my specific needs, it will always be the same device. – Chris Weiss Dec 8 '11 at 20:17
What boot-loader are you using on these machines? – Zoredache Dec 8 '11 at 20:24
Grub currently, but the best solution should be future-proofed against alternatives. – Chris Weiss Dec 8 '11 at 20:55

df -P / | tail -n 1 | awk '/.*/ { print $1 }'

Will return the root FS block device. Not necessarily the boot device though.

Better question might be why you're not scanning SMART on all the disks in the server?

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In my specific case, this is a script that will be deployed to hundreds of single-disk kiosk machines with either a SATA or PATA disk (so 99% of them would be /dev/sda or /dev/hda, I just want to make sure I don't miss the 1% that somehow ended up being /dev/sdb or something). Your solution almost works. Unfortunately, what I need is the boot device (That returns /dev/sda3, I just need /dev/sda). – Chris Weiss Dec 8 '11 at 20:07
cat /proc/mounts |grep /boot |awk '{print $1}'

Will return something like /dev/sda1 if your /boot is not on the root device.
Combine this with the answer from Chris S.

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