EECS Technical Database

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====== Frequently Asked Questions ======

== When logging into CentOS 7 indigo, I see an error: "WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! .............Add correct host key in $HOME/.ssh/known_hosts to get rid of this message .. What should I do? ==

This error occurs because indigo has a new SSH host key.  Please edit your "//known_hosts//" file on your local system, and remove entries relating to indigo (indigo,indigo.eecs.yorku.ca,eecs.yorku.ca). Now you will be able to login without the warning.
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== I had scheduled "at" and/or "cron" jobs on CentOS 6 indigo.  Will they be copied to the new CentOS 7 indigo? ==

At jobs and cron jobs are not transferred between systems.  You will need to //recreate// your at and cron jobs on the new system.
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== I run vncserver on indigo.  When I connect to my session with vncviewer, I don't see any output. ==

Remove the file ~///.vnc/xstartup// in your home directory, then restart vncserver on indigo.  A new .vnc/xstartup file will be created, and you will now be able to connect with vncviewer.  The old file which was created with the older vncserver is no longer compatible with the system setup.
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== Why does "svn" command fail with a shared library error under CentOS 7? ==

The local version of the //svn// command (/eecs/local/bin/svn) was compiled with CentOS 6, and this linked to an older version of a dynamic library (libsasl2.so.2) which has been updated on CentOS 7.  This is fixed temporarily on indigo.  However, /usr/bin/svn client (the one provided by the OS) will also work in the meantime. 
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==Shared Library Error on CentOS 7 using a haskel script==
/setup: error while loading shared libraries: libgmp.so.3: cannot open shared object file: No such file or directory

/eecs/home/sel/script/script which is using a haskell file setup.hs

Recommended- Can you trying setting the LD_LIBRARY_PATH and running your grading scripts.    //setenv LD_LIBRARY_PATH /eecs/local/lib64//

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== What happened to the Fortran compiler, f77? ==

The GNU Fortran compiler f77 has been renamed to gfortran under CentOS 7.  f77 version was 3.4.6.  //gfortran// version is 4.8.5.
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== Gnome Display Manager will not start up - Failure - unable to load a failsafe session==
This occurred because the .xsession was not set to the current default
Contained "exec /cs/local/share/system.xfce". Updated to the default(~template/.xsession)
//Many users still have this old profile// You can copy the// ~template/.xsession// to replace your existing one 
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==xterm: cannot load font 'MAIN_FONT'==
\\
You may be using an old ~/.Xresources file . Remove  ~/.Xresources 
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==How do I get the task bar to display my open windows==
From the Desktop icon at the top left, select and enter in the search bar "tweak tools" . //Here you can customize your desktop//
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==gedit over an ssh - X session Couldn't connect to accessibility bus Failed to connect to socket /tmp/dbus Error==
On CentOS 7 , you will get the following error if you run gedit remotely: (ssh to another host): WARNING: Couldn't connect to accessibility bus: Failed to connect to socket /tmp/dbus-xxxxxx: Connection refused
If you are using gedit on your desktop , it will work properly. You can choose to use another editor like emacs or geany.
You can workaround the "Failed to connect to socket.." by setting the environment variable "NO_AT_BRIDGE to 1"
eg : setenv NO_AT_BRIDGE 1 and then run "gedit"
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==Fail to launch Tweak Tool - LD_LIBRARY_PATH set to /cs/local.lib==
This failed because the script is python based and needs a module "gi"
If a user has his/her environment variable LD_LIBRARY_PATH set to /cs/local/lib, it will fail. The work around is to unset the environment variable and run gnome-tweak-tool . An alternative is to add the "gi" module to our installed python in /cs/local/bin

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====Gnome(3) Window Manager - Quick Tips====
==What is Gnome Shell?==
Gnome Shell is the graphical shell of the GNOME desktop environment.It provides basic functions like launching applications, switching between windows and is also a widget engine. Gnome Shell also differs from previous versions of GNOME by placing more of an emphasis on applications instead of just windows. The activities overview now groups windows by application. 

==What displays on the desktop by default?==
At the top, you will see the date at the middle and to the far right a couple more icons like sound, login,etc. The Lassonde Logo and hostname are displayed below.
In the box displayed under Username, you will enter your eecs username and then click the next button for a password. Enter your eecs account password. Next you click Sign in.
This will launch your default window manager.
If you click on the settings icon next to "Sign in", there is a dropdown menu with 2 options, a default and a failsafe. Default desktop is used but if you have a quota problem , you may want to use the "failsafe" desktop option. This will give you a "dumb" terminal to work with.
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==Once logged in , what do I see==
Your default Gnome Shell presents at the top left, an "Activities Icon", date stamp in the middle and to the far right a "Logout icon"
On the desktop default , you will see your "Home Dir" icon as well as "Trash"
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==What does the Activities Overview do==
The Activities Overview allows you to launch new applications, switch windows,
and move windows between workspaces. There are three ways to open the Activities Overview:
  * Click on Activities in the top bar
  * Use the hot corner in the top-left corner of the screen
  * Press the Super key
The Activities Icon will display the "Dash Dock" with default applications on the Left side of your desktop. From here you can select "Show Application" for applications your are looking for or use the search bar presented to find the application. The applications bar, known as the dash, only appears on the activities
screen. Using "Tweak Tool", you can make the Application Menu show on the Top Left 
replacing the Activities menu.
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==How do I get a terminal window==
Using the Activities Icon, Click on it and you will find your default applications.
(Firefox Browser, Thunderbird Mail, Terminal and "Show Applications"
Select Terminal to get one launch
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==What is "Show Applications"==
"Show Applications" will display all the applications available for your use. They are categorized by groupings such as Audio,Network,Graphics,Utility,etc
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==How do I logout of my session==
On the Far top right corner of the screen, you will see the logout icon. Once you click on it, you will see your user name. Using the pull-down option on the title bar with your username, you will see Logout. 
Click on logout .
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==How to customizing my Desktop Settings==
In order to customize some of your desktop settings use the Tweak Tools settings.
You can find "Tweak Tool" by:
a. Using the //Activities Overview//, the sidebar icons, select "//Show Applications//"
Type in the Search Bar "//Tweak Tool//" . Alternatively select "Utility Folder"
"Tweak Tool" can be located here. 
Alternatively , from a terminal prompt, type //gnome-tweak-tool//
From this window you can do customization to your window manager.
For example, if you want to re-instate your minimize and maximize button on a terminal window, Select "Windows" "Title Bar Buttons" Turn on Minimize and Maximize
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== How to obtain a task bar at the bottom of you screen==
From "Tweak Tools: Select **Extensions**, Windows List ON
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==How can I stop the cursor from blinking?==
You can disable the cursor blinking for all programs by running this
command from a terminal prompt ($)

//gsettings set org.gnome.desktop.interface cursor-blink false//
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==How to get a new terminal==
There are several ways to get a new terminal.
a.From a command line, type $ gnome-terminal 
b.You can right-click on the Desktop and select "Open Terminal". Alternatively "Open Tab"
c.From any Terminal prompt "Shift Ctrl N"
d. Right click on the desktop and select "Open Terminal"

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==How to display all my open windows==
//Alt-tab// . From the Windows tab, you can view your open windows. It only shows windows on the current workspace.
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==Important Keys to note==
The 'Windows' key provides the overview. Mouse moved to the top left corner
does the same. The windows key is also referred to as the "superkey"just move
the mouse cursor to the top left corner of the screen, which functions as a" hot
corner."
 
==How do I switch workspaces==
Ctrl-Alt-Up/Down: Switches between workspaces.
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==How do I switch between Applications==
Alt-Tab: Switches between apps.
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==How to Edit the Favorites" Application List==
This list appears in multiple places, in the same order. This appears as
Favorites in the "Applications" menu in the top Panel, and as the icons used
in the "Frippery Panel Favorites", and as the menu in the Overview overlay.
So, to edit it, use the following steps:
  * Press the Windows key on your keyboard (aka Super, Meta key) to get the Overview overlay
  * Right-click on each app in the left side-menu you don't like & remove it
  * Now open the Show Applications (nine white dots) icon
  * Right-click on each application icon & select "Add to Favorites"
  * Drag the Order  of icons up & up as you please
The order appears in all areas (Panel favorites, Applications->Favorites)
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