Lock remote deskop over ssh

I had a seemingly simple problem, connect over SSH to remote computer and lock the screen. Simple Google search for "gnome lock screen" yielded a plenty of results all of which revolving about using command gnome-screensaver-command -l.  First of, the package gnome-screensaver isn't installed by default on Fedora, meaning it isn't used there. Then, after installing it I got the following error message:

** Message: Failed to get session bus: Error spawning command line 'dbus-launch --autolaunch=062fabbac04041679f56c8db8593c352 --binary-syntax --close-stderr': Child process exited with code 1

Ok, turns out that session DBus is inaccessible and that gnome-screensaver-command just sends a message over DBus. Using d-feet it was easy to find out object, interface and method to use to lock the screen, but how to access DBus was a bit harder. The easy part was to find out that the key is in environment variable DBUS_SESSION_BUS_ADDRESS which has to point to a DBus daemon socket. But harder was to find where this socket is by looking into usual places on the file system. Finally, turned out that the easiest was to look at the environment of an existing process and get value from there, i.e.:

$ cat /proc/`pidof gnome-shell`/environ | \
              tr '\0' '\n' | grep DBUS_SESSION_BUS_ADDRESS
DBUS_SESSION_BUS_ADDRESS=unix:abstract=/tmp/dbus-dl1GC6PYCt,guid=33abd4a9e6bb3dee9262121d5819bdf1

tr command is necessary because entries in the environment are separated by NULL character (i.e. they are strings in C), so we are changing them into new line. Finally, grep just takes out the entry we are interested in. BTW, sorry for the useless cat use, but it is leftover as I constructed the command. :)

When you have properly set environment variable to access DBus, it is easy to invoke method Lock() that locks the screen, i.e.:

dbus-send --print-reply --session \
          --type=method_call --reply-timeout=3000 \
          --dest='org.gnome.ScreenSaver' \
          /org/gnome/ScreenSaver \
          org.gnome.ScreenSaver.Lock

and that will lock the screen. What's left to do is just to glue everything into a script:

#!/bin/bash
PID=`pidof gnome-shell`
DBUS_SESSION_BUS_ADDRESS=$(tr '\0' '\n' < /proc/${PID}/environ | grep "DBUS_SESSION_BUS_ADDRESS" | cut -d "=" -f 2-) \
dbus-send --print-reply --session --type=method_call --reply-timeout=3000 --dest='org.gnome.ScreenSaver' /org/gnome/ScreenSaver org.gnome.ScreenSaver.Lock

Just copy that into a file, make it executable and try it. It should work every time. :)

Gnome Shell's calendar and Thunderbird

After I installed Fedora 20, I noticed that the calendar in Gnome Shell's clock doesn't work, i.e. it doesn't show scheduled entries. Actually, this didn't work in the older version of Fedora, neither. But now, I decided to make it work. Before describing what I've tried, and what I did, I have to describe my setup. First of, I'm using Thunderbird. Evolution proved too unstable for me so I ditched it. Next, all my calendars are stored on Google, so, no local calendar in Thunderbird. The reason I'm using Google calendars is to be able to sync with mobile phone. The reason for local client, instead of Web client, is pure habit and comotion, I like more desktop clients than the Web based. Finally, I don't mind having some additional software being installed no matter if I use it directly or not. So, usually, I have Evolution installed alongside Thunderbird.

Gnome Shell's calendar allows integration only with Evolution, Thunderbird isn't allowed. This is actually expected, as Thunderbird is primarily mail application. But using Lightning plugin, it is a very good calendar solution, too. So, no easy way to define Thunderbird as default calendar application. After some quick googling, I found the following plugin for Thunderbird. Basically, it synces Thunderbird's calendar with Evolution's, one way, and that's it. When I wanted to install it, I had a small, and unrelated, problem. Namely, I could not find how to install it in Thunderburd?! There was no option in Thunderbird for managing Addons!? After some short Googling I finally realized that the menu option on the upper right hand side (icon with three parallel lines) isn't actually the full menu! I managed to open full Tools menu item by pressing Alt+F.

After I installed this plugin, and restarting Gnome and then Thunderbird, it didn't work So, the next I tried this. But first, I checked what was the current setting:

$ gsettings get org.gnome.desktop.default-applications.office.calendar exec
'evolution -c calendar'

Ok, now I changed the value using the following command:

$ gsettings set org.gnome.desktop.default-applications.office.calendar exec thunderbird

That didn't work either. It occured to me that the problem might be that I'm using Thunderbird profiles, so I also tried to define a profile in the command:

gsettings set org.gnome.desktop.default-applications.office.calendar exec 'thunderbird -P MyProfile'

Still, no luck! Then I went back to the plugin page and saw there that I have to create initial Evolution profile. I tried that too, but again, no luck. Maybe the problem was that I'm not using local calendars but remote ones. But then I realized that there is very easy solution. Namely, I created Evolution profile that is connected to Google calendars and synces with them. Google calendars are, in turn, connected to Thunderbird and everything works!

Yet, I didn't managed to get Thunderbird used when I click on Open Calendar option in the Gnome Shell's clock. Evolution is always used. Note that I tried two things, and both didn't help. First, I tried to define Thunderbird as default Calendar application using gsettings command as described above. Next, I tried to define Thunderbird default Calendar application in menu that is accessed by selecting All setting application, Details button, and there Default applications menu option. Note that Thunderbird isn't shown as a possible Calendar application. That is because its MIME type doesn't specify it as such. To change that I used procedure described here. In short, open file /usr/share/applications/mozilla-thunderbird.desktop in text editor and modify line MimeType so that it is

MimeType=message/rfc822;x-scheme-handler/mailto;text/calendar;text/x-vcard;:

Now, close text editor and update database file:

update-desktop-database -q

Finally, go to Details button and you'll see Thunderbird is now offered as a Calendar application, too.

In the end, I lost few hours investigating this and trying different solutions. Hopefully, someone will find this useful and will have to waste a lot less time.