Specifically, I've been trying to find what the possible values are for the property UDISKS_PARTITION_FLAGS. It seems to be set to "boot" if the partition has the boot/active flag set, and unset if not, but I'd like to find some documentation to that effect.

Google is unhelpful. I've downloaded and searched both the systemd source (which includes udev) and the kernel source, but found no match for the string "UDISKS_PARTITION_FLAGS". Where is the value of this property set? Where is it documented?


I've been using pyudev to access this property, and I thought it got them from udev. In response to the comments I've tried to get it to show up using

udevadm info --name=/dev/sda1 --attribute-walk

but I can't find the property in question there. However, looking at the link provided by slm in the comments, I found this command:

udisks --show-info /dev/sda1

The output has a partition section, where flags has the value boot. So it's really this value I want to find the documentation or source code for. It is only present for the partition that has the boot flag set.

  • Most udev rules reference data it's getting from sysfs. I'm not finding anything related underneath /sys on my systems with the word "flag" or "flags" in it. It might be something the distribution defined specifically for their purposes. What distro is this on?
    – Bratchley
    May 28, 2013 at 12:21
  • @Joel Ubuntu 12.04.2 LTS May 28, 2013 at 12:24
  • Take a look at this script, it shows how they're getting what you're asking about: forums.opensuse.org/english/other-forums/development/…
    – slm
    May 28, 2013 at 12:37
  • 1
    @slm Ha yeah I actually haven't even used Ubuntu for myself at all. I've been at the terminal a few times on other people's machines, but never more than that. Which is kind of surprising considering how often it gets mentioned and I know people who are card carrying members of the cult of Shuttleworth. I'll probably leave this installed so I have some vague point of reference for it. Only took me, what, 6 or 7 years to get around to installing it?
    – Bratchley
    May 28, 2013 at 13:09
  • 1
    @Joel I think I've found it myself. I'll post a self-answer in a minute. May 28, 2013 at 13:20

1 Answer 1


The udev properties with the UDISKS prefix is set by udisks 1.0.4, in src/helpers/partutil.c:1246. It is then picked up by udev somehow and stored in the property UDISKS_PARTITION_FLAGS, which can be found with this command:

udevadm info --name=/dev/sda1 --query=property

Here is the documentation for the property. Following the link to PartitionCreate shows that it may only be set to the value "boot" if the partitioning scheme is mbr, which is in agreement with the source code linked to in the first paragraph.

EDIT: Updated answer after comment from don_crissti.

  • @don_crissti Nice catch, I've updated my answer. Thank you! :) May 28, 2013 at 14:31

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