One of my biggest pet peeves as a Linux sysadmin is when I see users, or even other sysadmins using kill -9 on the first attempt to terminate a process. The reason this bugs me so much is because it shows either a lack of understanding of the kill command or just plain laziness. Rather than going on a long rant about why this is bad, I wanted to write an article about the kill command and how signal works in Linux.
Today is very much a “back to the basics” kind of day. In this article I am going to cover one of the most basic commands in Linux; the cd command. While today's article might be basic; it is always good even for experienced sysadmins, to look back at some of the basics and see if there are ways to improve your command line skills and Linux knowledge.
The Linux/Unix directory structure Before getting into how to change to another directory, let's take a minute to cover how Linux's directory structure is laid out.
Lately if you have been paying attention to tech or even mainstream media you might have seen a few stories about data breaches. Sometimes these data breaches have allowed attackers to gather unencrypted passwords or credit card numbers. In the past these types of attacks still happened, but there was not as many attacks as today and when they happened they were kept secret. With more and more internet based services becoming part of peoples lives, there is even more targets for attackers who are looking to get sensitive data.
Today's article is an item I covered briefly during my presentation at SaltConf 2014 (which was a pretty awesome conference by the way). One of the lesser known features of SaltStack is the ability to configure multiple master servers. Having an additional master server allows for some extra redundancy as well as capacity for large implementations. While I covered the benefits of having an additional master server in my presentation I didn't cover in full detail how to set this up, today I will cover the details of configuring multiple salt masters.
Shell scripting is a fundamental skill that every systems administrator should know. The ability to script mundane & repeatable tasks allows a sysadmin to perform these tasks quickly. These scripts can be used for anything from installing software, configuring software or quickly resolving a known issue.
A fundamental core of any programming language is the if statement. In this article I am going to show several examples of using if statements and explain how they work.
Recently I had moved my blog from WordPress to a custom python script that generates static HTML pages. After generating files I need to copy them to my web servers. While it is easy enough to FTP or SCP the files from my local machine to the remote web servers. I am looking for a little more elegant and automated solution. For that reason I have chosen to use the rsync command.
While taking a Red Hat Training course the instructor showed us a Yum plugin called verify. I've never used any of the Yum plugins before and after a while of playing with Yum Verify, I have decided that I should share this very cool plugin and introduce others to Yum plugins.
What are Yum Plugins Yum plugins are packages that can be installed to provide extra functionality to the Yellowdog Update Manager or yum.
In a previous article I covered a little bit about Symlinks and Hardlinks but I never really explained what they are or how to create them. Today I am going to cover how to create both Symlinks and Hardlinks and what the difference is between the two.
What are Symlinks and Hardlinks Hard Links In Linux when you perform an listing in a directory the listing is actually is a list of references that map to an inode.
Recently I was working on an issue where an application was not retaining the umask setting set in the root users profile or /etc/profile. After looking into the issue a bit it seemed that the application in question only applied the umask setting that was set in /etc/bashrc and would not even accept the values being the applications own start scripts.
After doing a bit of researched I learned a little bit more about what exactly these files do, the differences between them and when they are executed.
When supporting systems you have inherited or in environments that have many different OS versions and distributions of Linux. There are times when you simply don't know off hand what OS version or distribution the server you are logged into is.
Luckily there is a simple way to figure that out.
Ubuntu/Debian $ cat /etc/lsb-release DISTRIB_ID=Ubuntu DISTRIB_RELEASE=13.04 DISTRIB_CODENAME=raring DISTRIB_DESCRIPTION="Ubuntu 13.04" RedHat/CentOS/Oracle Linux # cat /etc/redhat-release Red Hat Enterprise Linux Server release 5 (Tikanga) Catchall If you are looking for a quick way and don't care what the output looks like, you can simply do this as well.