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I'm trying to install the Xeon Phi coprocessor. The specific behavior is probably related to the tools involved - my question is of a more general nature.

When I execute a command as root, I get a segmentation fault. When I execute it as root but (in my opinion unnecessarily) use sudo, it works:

i72:~ # whoami
root
i72:~ # micctrl -s
Segmentation fault
i72:~ # sudo micctrl -s
[no segfault]

What differences are there in the environments micctrl is being run in?

(Edit:) I think we ruled out environment variables as an option below.

The system is a SLES 11.2.

Thank you!

mrks
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2 Answers2

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sudo removes LD_LIBRARY_PATH, LD_PRELOAD from the environment (I suspect it does it for root as well as ordinary users). This may cause different libraries to be loaded for the program.

sudo can be configured on what variables it resets/clears - see http://brandonhutchinson.com/wiki/Sudo_and_environment_variables

Douglas Leeder
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  • Thanks. The environment variables are a good idea. `env -i bash` should recreate the same environment `sudo` uses, right? However, in that case, `micctrl -s` segfaults again. – mrks Apr 03 '13 at 15:40
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    @mdsl I'd go for `sudo bash` and then running `micctrl -s` and checking. – Douglas Leeder Apr 03 '13 at 15:59
  • Also, `sudo -E micctrl -s` does **not** segfault. – mrks Apr 03 '13 at 16:12
  • Since this is the only thing that actually changes, I believe that it is the correct answer. Accepted. – mrks Apr 07 '13 at 13:14
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Turns out that sudo just hides the "Segmentation fault" message. It still happens, but doesn't get displayed on the terminal. We found out because micctrl never gave us any output, even when it should have.

Edit: Also, if someone should run into the problem with micctrl: In our case, the Phi was not properly recognized by the system. lspci found it, but it was not listed in /sys/class/mic.

mrks
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