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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 …

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Articles in Monitoring

NFS I/O Stats with Logging

January 3, 2022 – 1:43 pm

The nfsiostat is an excellent tool for analyzing NFS performance. The only major problem with this utility is that it’s designed to be used interactively. It does not have logging or timestamping capabilities. I needed …

Finding Cron Jobs

September 9, 2021 – 11:28 am

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

August 11, 2021 – 11:10 am

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.

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.

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 …

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 …

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 …

Late Night Rant: College Admissions Scandal

June 23, 2019 – 11:11 am

This is America: you’re either a duper or a dupee. I’m a duper. You guys are the dupees.
— Frank Reynolds (Danny DeVito), It’s Always Sunny in Philadelphia
How will the 2019 college admissions scandal work out? …

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.

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.

Automating Web Page Screenshots

July 13, 2018 – 2:25 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, …

CLI System Monitoring Tools

November 12, 2017 – 12:24 pm
DSC_6236 copy copy copy copy copy

The multitude of sophisticated centralized monitoring tools available these days excel at one thing: telling you what happened while you’ve been sleeping. But what if you’re awake and need to know what’s going on right …

Watching VSFTP

November 8, 2016 – 10:56 pm

I have an FTPS server running VSFTP and below is collection of commands useful for monitoring activity and analyzing the logs.

Installing NetData on RHEL/CentOS

October 13, 2016 – 5:50 pm

NetData is a real-time system monitor great for visualizing performance data. Instances of netdata run independently on monitored systems. The results can be accessed remotely and grouped into a single dashboard view, making this tool highly scalable. …

Atop Script with Scheduling and Logging

August 3, 2016 – 7:35 pm

When something is going down on a server, the first thing most sysadmins will run is the venerable top utility. This happens automatically: if you suspect the server is being sluggish, your fingers just type top without you …

Monitoring Application Network Connections

February 11, 2016 – 3:12 pm
network switch

A Java application on one of my servers has been causing problems by opening up too many network connections and now closing them quickly enough. I needed to be notified when the number of connections …

Log Event Time Distribution (Part II)

November 11, 2015 – 2:30 am
time clock watch

Earlier I discussed a way to visualize frequency and distribution of messages in log files. Here’s a script to help you with that. Currently, the script works with two time formats: the one used in …

Upping the Soft nproc Limit

October 5, 2015 – 11:12 am

This is just a quick note to myself about increasing the “soft nproc” value. On one of the RHEL 6 Tomcat servers I got the following error when trying to “su – tomcat”:

Reduce SNMPd Logging Level

September 8, 2015 – 11:01 am

By default, (on RHEL/CentOS, at least) snmpd will log all connection attempts, which can turn your /var/log/messages into a giant mess, looking something like this…

Collectl & Colplot Sytem Performance Analysis Tools

August 26, 2015 – 11:17 am

It is not often that I run into Unix performance analysis tool that, a), I haven’t seen before and, b), is worth my attention. Collectl is both. It is a very useful combination of iostat, …

Dealing with Runaway Processes

July 14, 2015 – 10:46 pm

There is no official definition of a “runaway process”. Generally, it is a process that ignores its scheduled priority. It can also be a process that enters an infinite loop. Or it can be a process …