Scientific Linux 7

CLASSE has migrated to 64-bit Scientific Linux 7 (SL7). Any code built on an earlier SL distribution should run on 64-bit SL7. However, code built on 64-bit SL7 should only be run on 64-bit SL7. For notes on 64-bit computing, please see Lnx64Bit.

Migration Planning

For the main migration planning guide, please see https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/Migration_Planning_Guide/

Package and Driver Changes

For a list of package and driver changes in RHEL7, please see https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/Migration_Planning_Guide/chap-Red_Hat_Enterprise_Linux-Migration_Planning_Guide-Changes_to_packages_functionality_and_support.html.


Xfce is the default Desktop Environment on all CLASSE Scientific Linux 7. To change this setting, please see Setting Default Desktop Environment.

For more information about Xfce, please see XfceWM

Gnome 3

The default Gnome 3 desktop is a stark departure from Gnome 2 in SL6. Those who desire a more traditional desktop experience, should click on the gear and select "xfce" or "gnome-classic" in the login screen. For more, please see https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/Desktop_Migration_and_Administration_Guide/what-is-gnome-classic.html

A useful Gnome 3 cheatsheet can be found at https://wiki.gnome.org/Gnome3CheatSheet

Gnome (and KDE) will not work if you log in on the desktops of more than one computer at the same time. See MultipleSessions. Xfce and IceWM often are more appropriate in the CLASSE environment.

Setting Default Desktop Environment

To set the Scientific Linux 7 (SL7) Default Desktop Environment (just a bit different than SL6):

  • move the mouse (and/or click the left mouse button, as well)
  • click on "Not listed?" and type in your CLASSE username
  • then click on the "Next" button.

Now before you enter your CLASSE password:

  • please click on the cog or pinwheel icon just to the left of the "Sign In" button

This will list all the window managers available. Some of the choices you'll see are: KDE Gnome Gnome Classic Xfce icewm ...

  • so please select one

This will be your default Desktop Environment each time you login. You can change this setting anytime before you login by following the same procedure.

After choosing your Desktop Environment:
  • type in your CLASSE password
  • click on the "Sign In" button.

SSH Host key table change

When you SSH to a computer which was recently upgraded to SL7, you might get an error message which complains "WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!". If that happens to you, you might want to consider deleting the file /home/yourclasseid/.ssh/known_hosts

This error message happens because most CLASSE farm computers indeed have new SSH host keys. The upgrade procedure did not preserve those computers' previous SSH host keys.

As suggested in the full text of the error message, you can manually edit the file /home/yourclasseid/.ssh/known_hosts and update or delete that computer's host key. However, since the upgrades affected all of the Farm host keys, you might wind up doing a lot of editing. Although somewhat less secure, it might be a lot easier to just delete the file and let the SSH software automatically recreate it and add updated keys when you connect to the various Farm nodes.

Tab-key completion in bash

On SL7, there's a ton of completion rules that get installed by default at login that tweak the behavior in a bunch of ways. You can restore variable tab expansion, for example, by doing:

echo "shopt -s direxpand" >> .config/bash_completion

Software Documentation

For detailed information concerning Linux software avaible at CLASSE please see our Software Documentation wiki
Topic revision: r13 - 28 Apr 2020, AttilioDeFalco
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