When I type sudo nautilus, i get the following:

sudo nautilus

(nautilus:6269): Gtk-WARNING **: Failed to register client: GDBus.Errorrg.freedesktop.DBus.Error.ServiceUnknown: The name org.gnome.SessionManager was not provided by any .service files
sys:1: PyGIWarning: Nautilus was imported without specifying a version first. Use gi.require_version('Nautilus', '3.0') before import to ensure that the right version gets loaded.

** (nautilus:6269): CRITICAL **: Another desktop manager in use; desktop window won't be created
Nautilus-Share-Message: Called "net usershare info" but it failed: Failed to execute child process "net" (No such file or directory)

What am i doing wrong?

Nautilus was installed to my Ubuntu 16.04 system long ago and it's been used quite a bit, although not frequently enough to fully acquaint me with its operation; mostly it's been used to open locked files that were otherwise restricted.

I don't know for certain that this is the cause, but more and more DEs are putting obstacles in the way of using GUI applications as root. There's a long thread (it's too late for me to search for it, but you might try) regarding KDE's decision in the latest Plasma desktop to bar root from starting a file manager.

This thread from the Ubuntu forums might help: https://ubuntuforums.org/showthread.php?t=2324256

Supposedly this in the interest of security, but, as far as I can tell, it's not security--it's security theatre.

Please note anomaly in pasted terminal dialog above, i.e., 'GDBus.Errorrg' -- where the 'o' in org is a sleepy icon rather than the alphabetic character 'o' (oh) as it should be.

. . . This came straight from my Terminal and i did NOT add the sleepy icon as substitute for letter 'o.'

Does this mean my system is infected?

Clamtk sez no.

>frankbell

Thanks for your input, and i agree with your logic re 'security theater'

mike3644, you may want to take a look at midnight commander. It's a Linux command line file manager similar to the old Norton Commander for DOS (I admit it--I'm old). As it is a command line application, you can run it as root--I just tested it on Debian Sid. It's a little quirky compared to contemporary GUI file managers, but it's quite versatile.

It should be in the repos, probably as "mc."

Some of those are warnings are due to your not running the command using root's profile. You can use

sudo -i nautilus

The LQ website is automatically parsing characters into icons. There is nothing wrong with your system. If you select advanced when posting and disable similes in text it will not happen.