Chow Help Pages

Welcome to the new server for! These pages provide brief help about the main Linux system in the mathematics department at Johns Hopkins University.

The new server's operating system is Red Hat Enterprise Linux 6.2. There are many major or minor things that are different from the previous server. The general help pages are under construction. We outline some important things here. Feedback about these pages is very welcome. Please send comments to

Remote SSH login.

1. If you use SSH to connect to chow and you are not using the JH network (meaning you are off-campus and are NOT using the JH VPN), you must specify port 122 for SSH. This is a requirement from Network Security. On campus and via the VPN, both port 122 and the standard port 22 will work. If you use one setting for laptop, tablet, etc, use port 122 which always works.

2. SSH warning. The first time you use ssh to connect to chow after the migration (from any machine), you might get a wanring like below:

The RSA host key for has changed, 
and the key for the corresponding IP address 
is unchanged. This could either mean that 
DNS SPOOFING is happening or the IP address for the host 
and its host key have changed at the same time. 
Offending key for IP in /Users/username/.ssh/known_hosts:38 
Someone could be eavesdropping on you right now (man-in-the-middle attack)! 
It is also possible that a host key has just been changed. 
The fingerprint for the RSA key sent by the remote host is 
Please contact your system administrator. 
Add correct host key in /Users/username/.ssh/known_hosts to get rid of this message. 
Offending RSA key in /Users/username/.ssh/known_hosts:52 
RSA host key for has changed and you have requested strict checking. 
Host key verification failed.
In this case, do one of the following:


1. All email messages have been migrated to the new server. Your procmail and/or mail forwarding options were migrated as well.

2. Local program such as Pine (alias for Alpine) and Evolution work as usual (if you use Evolution, your mail data will be migrated to the new version the first time you use it).

3. Mail programs for IMAP/POP3 will work as usual. If you encounter problem getting new email from your mail program, you can delete and re-create the account on your mail program. Here is the configuration for mail client:

X-Window Connection

1. If you log into the graphical destkop environment, please note that the environment is completely new and was rewritten. It was not possible to migrate the old desktop configuration to the new server due to the many differences between the server software

2. There are two desktop themes. Gnome and KDE. If you log in Gnome and do not see the menu bar on top, instead you see menu bar on bottom (or worse, no menu at all), then you have some old desktop configurations that are not compatible with the new server. The easy way to get to the new menu to work is to rename the following directories (via SSH session), then log in X-window again. Or contact

        mv .gnome .gnome.old
        mv .gnome2 .gnome2.old

3. If you have a Linux terminal in your office, the X-connection will works as usual.

4. Here are some quick tips about X-connection to chow:

5. Because of  the new operating system. The previously X-Windows program (X-win32) does not work well. At this time we use the program Xming for Windows X-connection to chow. To use Xming, double click the "Chow" icon on the desktop. Once you finish your X-session, after log out from chow and Xming comes back with the login screen, right click the Xming icon on taskbar and choose Close to quit the program.

Math Software

Mathematica (version 9.0), Matlab (version R2012b) and Maple (version 16) have been installed.

Page last updated 2/8/2013.
Old chow help page.