Red Cloud Linux Instances

Linux Instances can be created and maintained on Red Cloud using the OpenStack Web Interface. This documentation assumes a basic understanding of OpenStack, so please review that page as needed. If you are new to Linux, you may want to read the Linux Tutorial first. It is also a good idea to be familiar with the Linux Tutorial if you have not previously done Linux system administration, which is an assumed prerequisite to managing Linux Instances. Additionally, you may find the Introduction to Linux topic on the Cornell Virtual Workshop helpful.

Creating a New Linux Instance

You can boot an instance with most modern Linux distributions. Currently Red Cloud offers pre-made VM images running the following Linux distributions:

• CentOS
• Ubuntu (including LTS)

Steps

1. Log in to the OpenStack Web Interface (check out how to log in if you need to)
2. If you have not already, create a Key pair
3. If you have not already, create a Security group. Note that your security group should include the inbound SSH rule so you can connect to it.
4. Optional: Set up a Private Network
5. Select Launch Instance from the Instances page
6. Follow the instructions about launching a new instance, and select one of the a CentOS or Ubuntu images under the Source tab
7. Optional: Create and attach a Volume
8. Optional: Associate a Floating IP address

Now that you have created and launched an instance, your next steps will be to connect to it and set up a new user account. See the CentOS steps or Ubuntu steps for more information on how to set up a new user, update, and install software for each distribution.

Accessing Instances

First, establish access to your instance using Secure Shell (ssh), possibly including X Windows for remote graphical display. If you are at all unfamiliar with Linux, we recommend following the Linux Tutorial. If you would like to have a desktop environment (not available by default for Linux instances), then you may want to follow the steps for XFCE Desktop on CentOS. Establishing an SSH connection is a prerequisite for creating a Linux desktop environment such as XFCE.

Secure Shell (SSH)

Be sure that the security group for your instance permits SSH connections (TCP port 22) from your current IP address. This section details specifics for connecting to Linux instances, and full instructions are provided on the Connect to Linux page.

Use the matching private key to the public key in the key pair you specified when launching the instance, log to your instance as root via ssh. For some images, you might have to log in as the centos or ubuntu user as prompted. Specify the key pair file (for example my_key.pem) when you ssh as follows:

 ssh -i my_key.pem root@<IP address of your instance>

Note: Transferring files can also be done over ssh. See the scp and sftp commands, or programs like WinSCP and similar software for Mac OS X.

Troubleshooting

• Check the instance's console in the OpenStack Web Interface. Did the instance boot successfully?
• Do the security group's rules allow incoming ssh connections (TCP port 22) from the IP address of your computer?
• Is your instance on the public network? If not, does it have an associated floating IP address?
• If you get an unexpected password prompt:
  • Did you use the correct user name?
  • Make sure your private key matches the public key of the key pair.
    1. On your computer, run: ssh-keygen -y -f <private key file>
    2. Does the output match the public key list here? https://redcloud.cac.cornell.edu/dashboard/project/key_pairs/<your keypair name>/

XFCE Desktop on CentOS

In case one would prefer a desktop environment over a command-line, this section details the steps to setting up an XFCE Desktop Environment on a CentOS 7.4 instance. Other typical Linux desktop environments, such as Gnome, are also available but XFCE is used as an example here. Additionally, setting up a desktop environment may work on Ubuntu instances as well, with some differences. Once the environment is set up, you can run a VNC server and connect to it through an ssh tunnel.

XFCE Setup

1. Log in as root via ssh as described above.
2. Install needed packages:
   • yum groupinstall xfce
   • yum install tigervnc-server
3. Install some additional software that most users will want. These are only suggestions, and this is not a comprehensive list
   • yum install gedit
   • yum install firefox
   • LibreOffice

VNC User Setup

For each user that will want to use the XFCE Desktop, you will need to set up VNC (Virtual Network Computing) cability. To do this, follow the directions below. Alternatively, there is also an Easy guide to secure VNC server with TLS encryption.

1. Open a shell as that user
2. vncpasswd
   • Sets the user's VNC password
   • This step is not necessary for read-only VNC
   • This creates a ~/.vnc folder
3. vim ~/.vnc/xstartup
   • Paste this text into the file:
     #!/bin/bash
     xrdb $HOME/.Xresources
     startxfce4 &
     
4. chmod 775 ~/.vnc/xstartup
5. mkdir ~/bin
6. vim ~/bin/start_vncserver.sh
   • Paste this text into the file:
     #!/bin/bash
     vncserver -geometry 1680x1050
     
7. chmod 775 ~/bin/start_vncserver.sh

Using VNC

A brief overview for users is provided here, and for more information please see the Using VNC section on our Getting Started page.

Manage the VNC Server

Whenever an instance gets rebooted, you can restart the VNC server by doing the following

1. ssh into the instance
2. run ~/bin/start_vncserver.sh

You can stop the NVC server by running vncserver -kill :1

To change or reset the VNC password, you can simply run vncpassword

To change the screen resolution:

• Permanently: edit the script ~/.vnc/xstartup
• For this session only: use Applications->Display

View the Desktop

1. Open a local shell and ssh to establish the tunnel (recommended local port 10000):
   • ssh -L 10000:localhost:5901 <remote ip>
   • Note: When this shell is closed, the VNC viewer will have to close, too, though VNC is still running.
2. In a VNC viewer app, connect to the VNC server localhost:10000 (or whichever port you chose above).
   • This should open a window showing the desktop
   • The first time you do this:
     • For the remote computer, you may have to dismiss a warning dialog
     • You will need to initialize a "panel". Click "Use default config"

Note for Windows users: You can also find useful instructions on the VNC Tunnel Windows page. You may also want to look into OpenSSH or Bash on Ubuntu on Windows.

Initialize and Mount a Volume

The instructions here are for formatting and mounting the ephemeral storage of an instance so it becomes available to you as a temp disk at a typical location. Similar instructions also work for attached volumes, though steps like these can only be performed if you have allocated and attached the volume through OpenStack, which can be done while the instance is running.

1. Set up file system
   • mkfs.ext4 /dev/vdb
2. Make a directory where device will be mounted
   • mkdir /<diskname>
3. Mount the device
   • mount /dev/vdb /scratch
4. To have the mount automatically renewed after reboot, add an fstab entry (this is a little dangerous)
   • vim /etc/fstab
   • Add a line with tab separations between four fields: disk device, mounted location, "ext4", "defaults":
     • /dev/vdb /<diskname> ext4 defaults