Yesterday while re-purposing a server I was removing packages with apt-get and stumbled upon an interesting problem. After I removed the package and all of it's configurations, the subsequent installation did not re-deploy the configuration files.
After a bit of digging I found out that there are two methods for removing packages with apt-get. One of those method should be used if you want to remove binaries, and the other should be used if you want to remove both binaries and configuration files.
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'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.
Recently while I was scouring through a spreadsheet of “unallocated” IP addresses, I thought to myself. There has to be a better way to manage an inventory of IP addresses, and while I'm at it maybe even provide a list of provisioned servers.
After some googling I found myself on RackTables.org the home of an open source project that aims to provide just what I was looking for. An Inventory system that tracks and manages Servers, Racks, IP Addresses and just about everything else in a data center.
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.
Systems Administration is changing, with the huge scale of internet company deployments and the popularity of cloud computing. Server deployments are often scaling faster than the systems administration teams supporting them. In order to meet the demand those teams are finding themselves changing the ways they have traditionally managed servers.
One of those changes is automation, where once a sysadmin would need to spend time installing packages by hand (via apt or yum) and modifying configuration files.
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.
Are you tired of trying to memorize tons of passwords on different systems? Or do you simply want to have a faceless user SSH between two systems without being asked for a password? Well you are in luck because today we will be covering SSH keys.
SSH Servers have the ability to authenticate users using public/private keys. In the case of pass-phrase less keys this allows users to ssh from one system to another without typing a password.