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Please provide Ubuntu documentation that refutes this: https://help.ubuntu.com/community/RootSudo Why, on my fully updated 13.04 system, does pkexec not function?

$ pkexec gedit somefile.txt
No protocol specified

** (gedit:13135): WARNING **: Could not open X display
Cannot open display: 
Run '/usr/bin/gedit --help' to see a full list of available command line options
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pkexec isn't a drop in replacement for gksu. It is not intended for you to manually run like that. –  psusi Jun 28 '13 at 13:40
    
I didn't ask about nor mention gksu. –  chili555 Jun 28 '13 at 14:33

1 Answer 1

up vote 4 down vote accepted

Why it doesn't work?

By default pkexec does not allow you to run graphical (X11) applications. From the man page:

 The environment that PROGRAM will run it, will be set to a minimal
 known and safe environment in order to avoid injecting code through
 LD_LIBRARY_PATH or similar mechanisms. In addition the PKEXEC_UID
 environment variable is set to the user id of the process invoking
 pkexec.
     As a result, pkexec will not allow you to run X11 applications
     as another user since the $DISPLAY and $XAUTHORITY environment
     variables are not set.
 These two variables will be retained if the
 org.freedesktop.policykit.exec.allow_gui annotation on an action is set
 to a nonempty value; this is discouraged, though, and should only be
 used for legacy programs.

As stated in the man page, you can make it work albeit I really don't know if this is somehow dangerous or recommended.

To enable gedit for example you can create /usr/share/polkit-1/actions/com.ubuntu.gedit.policy with the following content:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE policyconfig PUBLIC
 "-//freedesktop//DTD PolicyKit Policy Configuration 1.0//EN"
 "http://www.freedesktop.org/standards/PolicyKit/1.0/policyconfig.dtd">
<policyconfig>
  <vendor>gedit</vendor>
  <vendor_url>gedit</vendor_url>
  <icon_name>accessories-text-editor</icon_name>
  <action id="org.freedesktop.policykit.pkexec.gedit">
   <description>Run "gedit"</description>
   <message>Authentication is required to run Text Editor</message>
   <defaults>
     <allow_any>auth_admin</allow_any>
     <allow_inactive>auth_admin</allow_inactive>
     <allow_active>auth_admin</allow_active>
   </defaults>
     <annotate key="org.freedesktop.policykit.exec.path">/usr/bin/gedit</annotate>
     <annotate key="org.freedesktop.policykit.exec.allow_gui">true</annotate>
   </action>  
</policyconfig>

Then pkexec gedit should work as expected:

enter image description here

As you can guess, this will only make gedit work. In theory, if you added allow_gui to "org.freedesktop.policykit.exec" (the default action) this should work for all applications, but in my tests I got the same result as yours.

Why is pkexec prefered?

Here you can find a discussion about the strengths of pkexec.

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1  
So, for graphical applications, is gksudo preferred and NOT pkexec? –  chili555 Jun 28 '13 at 15:29
    
I guess so. If gksudo is available, it is a lot easier to use it instead of create single actions to each app you need to use (if there is not a "global" way to do it). –  Salem Jun 28 '13 at 16:52
1  
@Salem- Then I wonder why my answer was edited and approved to use pkexec when it is not intended to be used for graphical applications and, as you can read, didn't work. askubuntu.com/questions/313619/… There must be something I don't understand. –  chili555 Jun 28 '13 at 19:30
    
@chili555 If that edit was what motivated your question you should ask this at Meta. In 13.04 you either have to install gksudo or configure pkexec (you can also use sudo -i but that will not work with Alt+F2 aka "Run"). I find the first MUCH easier. If anyone thinks otherwise well... To me seems wrong to suggest something that will not work as intended, but I may be missing something... –  Salem Jun 28 '13 at 20:45
    
You and me both. I will ask in Meta. –  chili555 Jun 28 '13 at 21:01

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