DevOps: some people think it’s a hype, a sysadmin job redefined, other people believe it’s just another skill you get from some training or out of school. It’s neither. I personally would say it’s a combination of skills; you get some from school, other from formal training and the rest from the daily hands-on job.
Why is it not just some SysAdmin job redefined?
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A “classical” SysAdmin does not use complex automation tools. His/her usual job is to go from one node to the other and set configurations, install software and fix things that do not work;
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A normal SysAdmin job does not (usually) involve coding, apart from small scripts that run on individual nodes;
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The “classical” SysAdmin (usually) deals with physical nodes and a good part of his/her daily job is fixing storage issues (rebuilding file systems, restoring from backups), debugging various hardware incompatibilities and applying patches.
Why do (serious, formal) coding skills matter for a DevOps?
The current industry trend is to express infrastructure through Code. You can currenty spawn entire environments (e.g. in AWS) with properly sized hardware configurations and services installed through Code only; this is possible with Automation tools like Chef. This is not about simple scripting skills but there are no complex algorithms either.
As I have just mentioned, DevOps is defined through Automation as the node interaction is no longer almost entirely manual. One now runs commands to multiple nodes at once and employs various automated monitoring tools that raise alarms and (sometimes) trigger tasks that do fix those issues, including, but not limited to, scaling resources or even adding new nodes to some cluster.
Who needs DevOps skills? I think that any organization that employs a large computing environment, large enough that scaling through classical SysAdmin operations is no longer feasible or cost-effective. Or, for that matter, any organization that intends to move its infrastructure to the Cloud. Being a new position that cannot be put in the same category with Devs, SysAdmins or QAs, there may be difficulties in filling up the job requirements, the career path or even deciding the compensation, but things are starting to change.
This was my introduction to the DevOps concept. Thank you for your read!
Why would you need to add swap, you may ask (or not); nevertheless, the answer is that swap space is not added by default to any node in AWS or on any Cloud Provider. The reasons for this are many, the main one being, most likely, the complexity implied, along with the possibility of wasting storage resources. But anyway, one may get these days instances with 200+ gigabytes of internal memory, why would anybody still need swap?
Enabling swap can indeed be an option for nodes with 1-2 gigabytes of memory such as t2.micro, but not for production workloads due to the performance issues. If you want to put up a node for experiments, dev testing or qa, such instances are cost effective approaches for most use cases (t2.micro is also free to use, within limits, during the first year).
Note: When adding swap space to an EBS-backed node in AWS, please keep the EBS storage limitations in mind when going on with this approach.
Adding swap space (e.g. 1Gb) is possible with a few commands:
# dd if=/dev/zero of=/swapfile bs=1024 count=1048576 # mkswap /swapfile # swapon /swapfile # echo -e "/swapfile\t\tswap\t\t\tswap\tdefaults\t0 0" >> /etc/fstab
This creates a special 1Gb file in the root directory, tells the kernel to use it as swap space and adds this setup as default in /etc/fstab.
Just defining the swap space may not be enough for the desired setup. One may also want to alter the “swappiness” behavior – when memory pages are sent to swap to free up space for running applications. For this a certain kernel parameter, /proc/sys/vm/swappiness, must be altered to suit one’s needs.
This parameter contains a numeric value, corresponding to the minimum allowed quantity of free memory available before the kernel starts to swap pages. A value of “10” means that no memory pages will be sent to swap before the free memory drops under 10%. Using the console, the parameter can be set with sysctl:
# sysctl vm.swappiness=10
One may also add it to the system configuration so that it survives reboots:
# echo "vm.swappiness=10" >> /etc/sysctl.conf
Hope you enjoyed this one. Have a nice day!