Linux Servers
Student and Faculty Use Servers
The CS Department provides a Linux server for use by CS students and staff. Please read the following to learn how to connect to it.
You must be connected to the CS VPN to connect!
Linux Servers
linux.cs.odu.edu may be used to connect to our services.
This will automatically pick one of the servers shown in the table below, but if you wish to connect to a specific server you can also use one of the following:
callisto.cs.odu.edueuropa.cs.odu.eduganymede.cs.odu.eduio.cs.odu.edu
With these servers in mind, you can connect to them using an SSH client with these instructions
Common Questions or Issues
While attempting to connect to the servers, you might run into some issues. Some are listed here but if you run into any more you can contact us at root@cs.odu.edu .
Host Key Checking Failed
Problem
When our linux services recently migrated to a cluster of servers, the host keys associated with them changed. As a result, students who previously used ssh may receive one of the below error messages in their client since the migration:
In most linux environment using OpenSSH: Warning: Possible DNS Spoofing Detected!
Using PuTTY on Windows: a popup saying Warning - Potential Security Breach!
This is because your client is expecting the previous host key and not the new one. When this mis-match occurs, most ssh-clients by default refuse to complete the connection without intervention for security reasons.
Solution
If you are on linux using OpenSSH, the simplest solution is to remove the old host key:
ssh-keygen -R <hostname>
Replacing sol.cs.odu.edu and then reconnect.
If you are using PuTTY, simply click the yes button on the popup to update the cache of host keys and complete the connection.
Home Directory
When you log in to your Unix account, you are placed in your "home directory" (/home/$USER). This will be the main working directory every time you log in.
Your home directory is backed up so it is advised to keep your data here. What is more, your home directory is available as your Windows Z Drive , when connected to the CS network.
Unix Permissions
Security of your files is important and needs to be considered when working on the servers. To further understand how file permissions work in linux, you can read visit our Unix Permissions page.
Submitting cron jobs to the public Linux Cluster
This explanation applies to the following hosts:
callisto.cs.odu.edueuropa.cs.odu.eduganymede.cs.odu.eduio.cs.odu.edu
When you add a cron job to your crontab on one of the hosts in the cluster, by default that job will run on every host in the cluster.
If you want a job to only run on one host you can prefix your job with /usr/bin/rcron. This system has failover so if multiple hosts in the cluster go down as long as there is one host up your job will continue to run.
A job using rcron looks like this:
12 11 * * * /usr/bin/rcron myjob
If you want to run jobs on a specific host, you should do some sort of hostname checking in a script so that it will only run on the specific host that you want it to.