KrazyWorks

Validating HTTPS Cache Peers for Squid

January 6, 2020 – 12:38 am

I have a squid proxy server that uses a long list of authenticated cache peers in a round-robin configuration. The process looks something like this:

Updating PHP 5.6w to 7.1u on CentOS 6.10

December 30, 2019 – 9:53 pm

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

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

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

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

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

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

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

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

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 …

Working with iptables Logging

November 30, 2019 – 9:41 pm

Most commonly iptables is used to allow, block, or redirect connections. However, it also has a logging feature that can be very useful for network traffic analysis and system security.

Copying File Attributes Across Servers

November 29, 2019 – 9:40 pm

To make long story short, had to fix someone’s chmod -R 777 /. A late-night copy-paste fail, it would seem. Needless to say, console access is required, as SSH will not work with permissions on …

CD/DVD-to-ISO Helper Script

November 27, 2019 – 9:39 pm

I can’t recall the last time I needed to convert a CD to ISO. I have four laptops and not one even has a DVD drive. It took me a while to find an external …

Analyzing Network Performance

November 25, 2019 – 9:37 pm

Much of network performance analysis will be comparative in nature. Thus, seeing the output of multiple commands side by side can be quite useful. Bash has a useful little utility called pr and we’ll make …

Copying Data in a Restricted Environment

August 17, 2019 – 8:04 pm

Consider this not-so-hypothetical scenario: you have some data on server_a that you would like to copy to server_b. Unfortunately, these two servers cannot communicate with each other. Nor do they have access to any common …

Raising Dead Services

August 15, 2019 – 2:23 pm

I suppose you may say all of this can be just as easily done via systemd service config files. Well, yes and no. Yes, it can. And, no, not as easily. Not even close. Because …

IMDb Movie Title Parser in Bash

July 12, 2019 – 7:19 pm

This is an update to the IMDb parser I wrote years back. From time to time IMDb makes small changes to their setup that break my script. This time they decided to start blocking curl, …

Sending Windows Logs to Remote Syslog

July 6, 2019 – 11:21 am

Nothing fancy here: just a quick note on directing Windows event logs and select application logs to a remote syslog server.

Plugging iPhone’s Privacy

July 3, 2019 – 11:19 am

Many recent publications , , suggest the iPhone is full of security holes threatening your privacy. The threat seems to be coming not so much from the phone’s operating system, but from the apps, …

Squeezing Video Files

June 30, 2019 – 11:16 am

All that crap I’ve been saving from YouTube, Facebook and whatnot tends to add up. As quality is not a huge concern here (not that it was very high to begin with), optimizing those video …

Finding Passwords in Logs and Shell History

June 27, 2019 – 11:15 am

Sooner or later it will happen: you type something after which you expect a password prompt then, without looking, you type the password. However, you fat-fingered the first command, and your password ended up in …

Anatomy of Internet Bullshit

June 25, 2019 – 11:12 am

Here’s an oldie from two years ago that reared its ugly head on Pocket: Starting Your Day on the Internet Is Damaging Your Brain, by Srinivas Rao. The author presents his personal opinion that reading …

Commands & Shells »

Plundering Facebook Photo Albums

Let’s imagine you need to download all the photos in a Facebook photo album. It can be a public album, a friend’s, or even your own. Sure, you can do this manually, but you probably …

Scraping a Web Page in Bash

Just a scripting exercise because I need to do something important, but I am procrastinating. The idea is simple: grab some URL with text containing somewhat structured data and convert it into a spreadsheet. I …

Processing Videos with ffmpeg and Lightroom

On occasion I wondered how to apply advanced photo filters to my lackluster GoPro and drone videos. You know, not the basic exposure/contrast/saturation or the cheesy special effects you find in video editors, but something …

Searching Twitter

Here are just a few hopefully useful tips for searching Twitter to get more relevant results and buy cheap twitter followers.

Scraping a Web Page in Bash

Generating Random Text Files for Testing

Sometimes you need dummy folder structures populated with random data for testing your various scripts and processes – backups, file transfers, encryption, compression, etc. Every time I need something like this, I end up writing …

Finding Cron Jobs

Cron is an indispensable tool for system administration. The difficulties in working with cron in a large environment stem from its decentralized nature. Cron jobs multiply like rabbits, and keeping track of them is not …

Understanding Memory Utilization in Linux

This is a depressing – and all-too-common – scenario: a user runs the free command and opens a support case because he sees zero “free” memory on the server.

Validating HTTPS Cache Peers for Squid

I have a squid proxy server that uses a long list of authenticated cache peers in a round-robin configuration. The process looks something like this:

Verifying SNMP Connectivity on Multiple Hosts

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.

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