I solved my problem but I want to know what caused it for any future reference and better understanding.
I have come across a strange behavior of Firefox on Ubuntu 14.04. I left office with my laptop turned on so I could listen to music. Before I left office, Firefox was working normally.
Now I came to library, opened my laptop and Firefox and what happened was that Firefox was unable to open any pages, including Google.com. Firefox was running smoothly, without any delays, it just returned Server not found on any page I tried. What I did was, as usual in such cases, restart
NetworkManager with command
sudo killall NetworkManager
which also automatically starts
NetworkManager after it. The laptop connected to network, I relaunch Firefox and again nothing. So I ran
ps auxw | grep firefox
to see if there is some strange Firefox background process running but everything appeared as usual. I am sorry but I didn't take a screenshot, my mistake. I closed Firefox and executed
ps auxw | grep firefox again and as expected, there was only one output line like this
campovs+ 2715 0.0 0.0 5924 2196 pts/0 S+ 16:43 0:00 grep --color=auto firefox
which means that
grep was searching for
At this point I was 100% sure there has to be something with the internet connection and not Firefox. So I decided to proceed with regular internet connection checking, that being executing
Packets were flying which also eliminated possible DNS errors, although I have no idea how those could happen since I haven't done anything on my laptop and the network I was connected to was eduroam. I ran another command
curl -v google.com
and it, as expected, returned HTML code of
google.com with last line
* Connection #0 to host google.com left intact
which basically means everything is ok. I was left out of options and I knew that restarting the laptop will almost certainly solve the problem, although I didn't even know what was causing it. I ran
sudo reboot and now Firefox is working.
So my question is, does anyone of you know, what might cause such behavior?