Ubuntu – Why is gksu no longer installed by default

Both files point to the same place:

$ ls -l /usr/bin/gksudo 
lrwxrwxrwx 1 root root 4 2010-09-27 18:23 /usr/bin/gksudo -> gksu

... gksudo is symlinked to gksu. But this doesn't mean they do the same things, far from it.

Applications can detect the command used to run it. This is typically argv[0] in C-style languages or $0 in Bourne-style shell scripts. The application can look at that and in this case, actually it changes how it works. The first indication of this is in the man gksu page:

gksu  is  a  frontend  to  su  and gksudo is a frontend to sudo.

If you look in the source (apt-get source gksu) for run_mode, you'll see how it detects this:

  { /* support gksu_sudo_run */
    gchar *myname = g_path_get_basename (argv[0]);
    if (!strcmp(myname, "gksudo"))
      run_mode = SUDO_MODE;
    g_free (myname);
  }

You can override this with the --su-mode/-w and --sudo-mode/-S arguments (so you can run equivalent commands without needing the gksudo symlink... But that's up to you.

If you want to know how these "modes" really differ, there's only a bit of escaping in gksu. You need to follow it into libgksu. This is the library that actually checks permissions before handing off to the system.

If no mode is specified (eg you call gksu without arguments) by the time it reaches libgksu, it will check Gconf (as Stefano points out) and if it still can't decide, it'll default to the su mode.

The issue with using a straight sudo nautilus is that it will sometimes try to use configuration files from your user's home directory. This can cause root (superpriviledged user) to change permissions on files within your home directory. This is not usually harmful long-term; it can cause annoying problems like refusing to login to your desktop, but you can usually restore previous configurations by typing:

sudo chown -R user:user ~/

So what gksudo and sudo -i do is simply to tell the program to run with either copies of .Xauthority and other configuration files or with ones that actually belong to root. I personally prefer sudo -i so I don't have to type in my password every time, but it's totally preference. The two commands are doing the same thing.