mjhjmtu

Every time update-grub is run all hard drives are scanned. Each drives that is in standby state will spin up to go idle. This is a waste of energy. We use update-grub version 1.98:

# update-grub -v
grub-mkconfig (GRUB) 1.98+20100804-14+squeeze1

Regression

1. There is a GRUB_DISABLE_OS_PROBER=true option in the /etc/default/grub file. But that seems to only work from version 2 and up. At least it doesn't stop scanning all drives in our version 1.98.




2. There is a /etc/grub.d/20_linux_xen script that might be run as a part of update-grub. After removing execute rights for all users with chmod a-x /etc/grub.d/20_linux_xen all drives do still spin up.

How to stop update-grub from scanning each and every hard drive?

In file /etc/grub.d/30_os-prober the line

OSPROBED="`os-prober | tr ' ' '^' | paste -s -d ' '`"

makes all drives spin (standby -> idle). Os-prober is a utility to find Linux installations at drives other then your boot drive. It is the os-prober that needs to be disabled.

1. One way is to remove the package: apt-get --purge remove os-prober.


2. Another way is to remove executable rights for os-prober. First find the location of os-prober using $ which os-prober. Output might look like: /usr/bin/os-prober. The remove the executable rights for all users for that file: # chmod a-x /usr/bin/os-prober
   


3. Another way is to remove executable rights for 30_os-prober. Find the location of 30_os-prober using $ locate /30_os-prober. Output might look like: /etc/grub.d/30_os-prober. The remove the executable rights for all users for that file: # chmod a-x /etc/grub.d/30_os-prober
   


4. Yet another way is to skip the execution of /etc/grub.d/30_os-prober. For example by making the GRUB_DISABLE_OS_PROBER=true option work in our grub version 1.98. This can be done by inserting in file /etc/grub.d/30_os-prober the code below the line set -e:

...

if [ "x$GRUB_DISABLE_OS_PROBER" = "xtrue" ]; then
 exit 0
fi

For those wondering if it's really worth the effort, yes it is. Perhaps not for energy saving but today I encountered a problem with update-grub as it wanted to probe for both /dev/sda (my harddisk) and /dev/sdc (a USB-stick). Without the latter inserted into my laptop, update-grub would hang, even though there is actually no OS on my USB-stick installed nor did I ever boot from this stick. As the USB-stick recently broke, I needed a way for update-grub to continue (alive) without it. Fortuately, GRUB_DISABLE_OS_PROBER=true just did the trick. :)

(Is this really worth the time and effort to fix?)

As you mentioned, the probing is probably happening when grub-mkconfig calls grub-probe. You could modify grub-mkconfig by simply hardcoding the result of the grub-probe calls. It is used to fill GRUB_DEVICE, GRUB_DEVICE_UUID, GRUB_DEVICE_BOOT, GRUB_DEVICE_BOOT_UUID, and GRUB_FS.

See my solution here to selectively disable which partitions are checked by os-prober with a small patch.

The configuration of GRUB_OS_PROBER_SKIP_LIST="UUID@device_path" in /etc/default/grub:

• reduces the numbers of devices in $OSPROBED used by /etc/grub.d/30_os-prober




• which stops the check with $grub_probe --target=fs_uuid --device