Featured »

March 2, 2022 – 2:00 pm

Books have been written on the subject of awk and sed. Here’s a small sample of commands I put together over the years that are useful for everyday system administration tasks. Most of these tasks …

Read the full story »
Networking

Unix and Linux network configuration. Multiple network interfaces. Bridged NICs. High-availability network configurations.

Applications

Reviews of latest Unix and Linux software. Helpful tips for application support admins. Automating application support.

Data

Disk partitioning, filesystems, directories, and files. Volume management, logical volumes, HA filesystems. Backups and disaster recovery.

Monitoring

Distributed server monitoring. Server performance and capacity planning. Monitoring applications, network status and user activity.

Commands & Shells

Cool Unix shell commands and options. Command-line tools and application. Things every Unix sysadmin needs to know.

Home » Archive by Month

Article Archive for December 2019

Updating PHP 5.6w to 7.1u on CentOS 6.10

December 30, 2019 – 9:53 pm
wvtchvkz4f4ua8we5yngswc1mkd[1]

This is mostly just a note to self. As I mentioned previously (probably more than once), I very much dislike systemd and will stick with CentOS 6 for as long as possible. Having said that, …

Analyzing atop Logs with atopsar

December 26, 2019 – 9:52 pm
0h7vjqy3irb9p63bjuuxvd0tq85[1]

I have discussed atop previously but concentrated primarily on how to run it and how to collect data. Now I’d like to spend some time talking about ways to analyze the data collected with atop.

Appending Filenames

December 22, 2019 – 9:51 pm
gk5arsj5ijgmshcbh73vvpkdh2k[1]

If you google how to append, say, current timestamp to the filename in Bash, almost every suggestion boils down to something really basic along the lines of mv $somefile $somefile_$(date +’Y%-%m-%d’). Technically, this is correct …

Verifying SNMP Connectivity on Multiple Hosts

December 19, 2019 – 9:50 pm
Photo-2019-10-07-14-39-03_0266[1]

I needed to check if SNMP was accessible on whatever live servers that existed in a particular subnet. Here’s a quick script to do this.

Selecting Time Ranges from Logs, Part 2

December 16, 2019 – 9:47 pm
4bbqfrqoa4vxlgrr02pg883ozks[1]

A couple of years ago I wrote an article about selecting specific time ranges from log files. I proposed two options: either convert all timestamps to epoch format (a CPU-intensive process) or rely on regex …

Bulk-Adding IPTables Rules

December 12, 2019 – 9:46 pm
b3gk9tc9x14ki5xa4bx8c4v1b66[1]

I’ve been using my mod of this handy script to block countries with iptables. One issue with the script is that it is adding rules one-by-one using the iptables -A syntax. This is the proper …

Automatically Block Frequent Visitors

December 9, 2019 – 9:45 pm
gea59uduencunzibzb6i3gxn36m[1]

I had a few similar scripts floating around this site, but this one is a bit more all-inclusive and better organized. The script will analyze your firewall/whatever access log and block particularly active visitors.

Windows 10 Upgrades

December 6, 2019 – 9:44 pm
img_0002[1]

I did the only sensible thing and disabled automatic updates on my two Windows 10 laptops. Microsoft’s belated foray into the world of CI/CD for releasing Windows patches suffers from limited automated testing.

Detecting Blurry Photos with ImageMagick

December 3, 2019 – 9:43 pm
ll7je7yy7kvxsiw8ibssm0nmqf0-2[1]

Here’s a typical scenario: I go to a birthday party where everyone knows I’m a shutterbug, so I have to bring my camera. As time goes by and blood alcohol concentration rises and attention to …