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April 17, 2019 – 4:51 pm

Just a quick collection of notes on – rather than a definitive guide to – setting up an SSH chroot jail on RHEL 6. The same should work on RHEL 7 and unrelated flavors. For …

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Articles in SysAdmin

Adding and Removing sshd instances on CentOS 6

April 20, 2019 – 8:24 pm

This is a process and a couple of script to allow you to setup an additional sshd service on an alternate port.

Creating a Chroot Jail for SSH Access

April 17, 2019 – 4:51 pm

Just a quick collection of notes on – rather than a definitive guide to – setting up an SSH chroot jail on RHEL 6. The same should work on RHEL 7 and unrelated flavors. For …

The Unix Oriental

April 14, 2019 – 4:16 pm

Placed quite appropriately in the “Security” category – my favorite Oriental cocktail recipe. Distinguishing it from the classic preparation, are absence of sweet vermouth and lime juice, as well as addition of just a couple …

Notes on ownCloud configuration

April 12, 2019 – 4:13 pm

The ownCloud file sharing application has been around for some time now, but somehow evaded my attention. My limited imagination makes me say “think of it us Dropbox hosted on the server in your basement”.

Encrypting Log Data During Log Rotation

April 9, 2019 – 4:12 pm

Most log files do not contain personally-identifiable information or other sensitive data. And even if they do, encryption of all personal data is not mandatory under GDPR. Still, on occasion, for testing and troubleshooting purposes …

DevOps Obfuscation

April 6, 2019 – 4:10 pm

Some years ago I’ve been reading “DevOps in Straight English” by Magnus Hedemark  and encountered the Release Frequency vs. Risk chart that supposedly illustrated the advantages of DevOps. It seemed convincing enough to not give …

Gnuplot with Bash

April 2, 2019 – 4:08 pm

OK, so both of these things have been around forever and will be around long after we’re gone. It’s worth your time to learn how to use the to together.

Multi-Dimensional Arrays in Bash

March 30, 2019 – 4:06 pm

Bash does not support multi-dimensional arrays, but there is a way to imitate this functionality, if you absolutely have to.

Asciinema Notes

March 27, 2019 – 4:04 pm

Asciinema is an awesome tool for recording your console sessions. It’s great for documenting processes and, in general, showing people how shit works: one look is worth a thousand words, as they say. Unfortunately, I …

Late Night Rant: Facebook

March 25, 2019 – 4:15 pm

According to media reports, since 2012, millions of Facebook and Instagram logins and plaintext passwords have been sitting on some internal Facebook system, accessible by  thousands of the company’s employees.

Measure DNS Server Performance

March 25, 2019 – 4:04 pm
Tangled FX 2.1.2 (Jan 10, 2019 at 6:31:40 PM)
B & W Etching preset

This is not an entirely proper way to benchmark a DNS server, but, in a pinch, it should give you some idea of its responsiveness and stability.

File Compression Testing

January 27, 2019 – 5:29 pm

For some reason I haven’t used zip much on Linux, sticking to the standard tar/gzip combo. But zip seems to be a viable alternative. While not as space-efficient, it is definitely faster; syntax is simple; …

Killing Process Network Access

January 27, 2019 – 4:45 pm

Imagine this scenario: a particular process on your server is connecting to a host outside your internal network and you don’t like that. On the other hand, you can’t just kill that process because you need it.

Installing t CLI power tool for Twitter

January 21, 2019 – 4:41 pm

The ‘t’ is an excellent Ruby-based CLI utility for interacting with the Twitter API written by Erik Berlin. This is certainly not the only such tool available, but, in my estimation, it is the most full-featured and expertly-written. No amateur-hour coding here.

Keeping Abreast with Filesystem Changes

January 17, 2019 – 4:39 pm

The inotify is a Linux kernel sybsystem for notifying user-space applications of filesystem changes. I always thought this exceptionally handy utility was under-appreciated or at least underutilized.

Inventory Network Services with Nmap

January 14, 2019 – 4:32 pm

With the growing number of network-enabled devices in your home, meaningful security becomes elusive. The first step to addressing the situation is knowing what you have. A few examples below use the nmap utility to scan your local network and detect active devices and services.

The Facebook Fracas

January 9, 2019 – 4:48 pm

The Facebook privacy saga is getting ridiculous. You’re using a free service that you signed up for – nobody was holding a gun to your giant head. And it’s not Gulag either: just delete your profile, uninstall the damned app, and forget Facebook ever existed.

Removing Chef Server Installation

January 9, 2019 – 4:44 pm
House cleaning product on wood table

Just a quick note on how to completely remove (more or less) Chef server installation from a CentOS/RHEL box.

Auto-Update /etc/hosts

January 9, 2019 – 4:39 pm

This was a silly solution to a silly problem, but may come in handy in the future for other things. A user process was establishing frequent connections to a handful of FQDNs. Not having any IP caching capability, every connection attempt was preceded by DNS lookup.

Find Large Folders

January 9, 2019 – 4:37 pm

When you get a filesystem space alert (and they tend to arrive at 3:37 on Saturday morning), deleting various supersized log files is one option I already covered in adequate detail. That is if you get so lucky as to find such a file to delete…

Automating Web Page Screenshots

January 9, 2019 – 4:22 pm

Automatic Web page screenshots are commonly used for various monitoring tasks, such as detecting copyright infringement, website defacement, and other legal and security matters. Automatic screenshotting can also be a useful tool for researchers, developers, and journalists. There are free and open-source tools out there that can help you automate the task of creating Web page screenshots.

The Future of Spaghetti Code

August 18, 2018 – 4:20 pm

In his new book “The Future of Work: Robotics, AI, and Automation”1, Darrell West of the Brookings Institution makes some very extravagant predictions. Here’s a short but entirely sufficient summary from the book’s presentation by …