Code Snippets

Restart Services On RackSpace Managed Nodes That Require sudo Rights

Recently I was working on a project that was using RightScale to manage RackSpace cloud nodes. One of the requirements of the project was to have application nodes scale automatically thus they were required to automatically install software, configure settings, and start services automatically on the RackSpace CentOS nodes being used. Most everything was fairly straight forward however some of the services we were using would not start properly and initially because of the lack of logging from the services we were unable to figure out what the problem was. Below I describe the problem in more detail along with the solution which involved updating a configuration file on the CentOS Linux servers and then restarting the services.

Technology Insights

Send A Text Message From A Shell To A User Logged Into A Linux Server

This topic is fairly known to most older system administrators however I doubt it is used very often anymore. If you happen to manage any servers where there are typically various people logged in and working on different items from the CLI then it can be useful to be able to send them messages. Using the write command you can send messages to users logged in on specific TTY port or by username. Below are a couple examples of how you would use the write command from a Linux shell.

Technology Insights

What do pts and tty Mean on Linux? What is the Difference Between The Two Terminal Types?

I have been asked the question numerous times of what PTS and TTY mean in Linux regarding terminals. People ask because they may be newer to Linux and learning how to view a process list they may actually see a serial connection, SSH connection, or a telnet connection in the process list that might show something like pts/0, pts/2, tty1, or tty2 in the TTY column. Most processes will just have a question mark in this column but if something is connected to an actual terminal then it will list where it is connected in the TTY column of “ps”.

Technology Errors

sudo: sorry, you must have a tty to run sudo

I was recently working on a Perl script that would SSH to another server and run a sudo command on the remote server that was failing. The error that was received is below.

Error: sudo: sorry, you must have a tty to run sudo

The reason for this is an update along the way with sudo locked it down further by adding the below line to /etc/sudoers configuration file.