![8vl3onvznkopxa6ny9995yrc4gw[1]](https://i0.wp.com/www.krazyworks.com/wp-content/uploads/2021/10/8vl3onvznkopxa6ny9995yrc4gw1-175x150.jpg "Awk & sed Snippets for SysAdmins")
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 »Upping the Soft nproc Limit
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”:
Create ISO Images
The genisoimage has been around for a few years, but is relatively little-known. It is a pre-mastering program to generate ISO9660/Joliet/HFS hybrid filesystems and is particularly good for creating portable data backups. Here are a …
Hold Off on iOS 9 iPhone Upgrade
If you haven’t updated your iPhone 6/6 Plus to the recently-released iOS 9, I’d suggest you hold off for a few weeks. Several bugs – including a significant security hole – have surfaced that will …
Removing Metadata from Images
Phones and cameras record a surprising amount of personally-sensitive information with the photos they create. This data includes timestamps, GPS coordinates, software used to process the images and lots of other details you may not …
Reduce SNMPd Logging Level
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…
Arthemia jCarousel Number of Posts
This is primarily just a note to myself on how to change the number of visible items in the jCarousel implementation for the WordPress Arthemia theme. Recently I finally updated to the current version and …
Tuesday Night Rant: LED Light Bulbs
An off-topic for sure, but after a brief conversation about LED bulbs with a friend – a Contract Electrical – I found I had more arguments then I was willing to spill on Facebook. I …
Linux CLI Network Speed Test
The speedtest.net is probably one of the more popular bandwidth testing utilities, Unfortunately, this and many other similar tools require a Web browser with late-version Flash or Java support, which can be problematic on Unix …
Collectl & Colplot Sytem Performance Analysis Tools
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, …
Installing Perl Modules with YUM
Just a quick note on how to install Perl modules with YUM. Due to differences in the naming conventions, YUM package name for a Perl module may differ from the the module’s native name in …
Brief Guide to PDSh
PDSh (Parallel Distributed Shell) is a high-performance parallel remote shell utility allowing you to execute commands on multiple remote hosts simultaneously. The utility was originally developed by LLNL and is currently available under GNU CPLv2. …
Dealing with Runaway Processes
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 …
Find Available IP Addresses
After a while, available IP addresses on the subnet may become hard to come by. Whatever spreadsheet you used to track IP allocations is likely out of date. Here’s a simple script that will scan …
Multi-Cluster Ganglia Configuration
I’ve discussed Ganglia configuration and RHEL/CentOS installation in the past. The usual structure is where every node belongs to one cluster. Recently I ran into a requirement to have nodes assigned to more than one cluster. …
Enabling dmesg Timestamps in RHEL
By default, CentOS/RHEL dmesg timestamps are disabled. Here are the instructions to enable timestamps and a quick script to display time in a human-readable format.
Practical TShark Capture Filters
The tshark is the command-line interface for Wireshark – a popular open-source network packet analyzer. A seemingly infinite variety of options make tshark an unlikely choice for casual use. Nevertheless, the power of CLI justifies the extra …
Raspberry Pi 2 OpenELEC Player
Just some quick documentation, mostly for myself, but feel free to try. This is a Raspberry Pi 2 with OpenELEC. The design is intended for overclocking, good wireless performance, and convenience of dual remotes. This …
Saving Postfix Messages
Sometimes for testing purposes you need to save all messages going through Postfix active queue. There are a couple of ways of doing this.
Simple Statistical Functions in Shell
Here’s a small collection of basic statistical functions you can use in your shell scripts. This may come in handy when analyzing disk space, system performance, etc.
Detecting Synology NAS with nmap
Just a quick note for myself on how to find Synology NAS servers on the network without having to use the bulky Windows utility that ships with these systems.
Dealing With Prolific Emailers
So you come back from vacation, open Outlook and see thousands of unread emails. Who sends all this stuff? There’s an easy way to identify the sources of this background noise. In Outlook’s inbox, select …
Regex Collection
Just a small collection of POSIX regular expressions that may come in handy for writing sysadmin scripts.
Commands & Shells »
Plundering Facebook Photo Albums
![wyryr1sn52gntzn65v4fpz5lc6v[1]](https://i2.wp.com/www.krazyworks.com/wp-content/uploads/2021/08/wyryr1sn52gntzn65v4fpz5lc6v1-80x80.jpg "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
![clfud46mxf2t5zph2l04zlpgl1d[1]](https://i2.wp.com/www.krazyworks.com/wp-content/uploads/2021/08/clfud46mxf2t5zph2l04zlpgl1d1-80x80.jpg "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 …
Applications »
Processing Videos with ffmpeg and Lightroom
![DSCF5361[1]](https://i1.wp.com/www.krazyworks.com/wp-content/uploads/2020/10/DSCF53611-80x80.jpg "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
![Cat-Devouring-A-Bird-Pablo-Picasso[1]](https://i0.wp.com/www.krazyworks.com/wp-content/uploads/2020/10/Cat-Devouring-A-Bird-Pablo-Picasso1-80x80.jpg "Searching Twitter")
Here are just a few hopefully useful tips for searching Twitter to get more relevant results and buy cheap twitter followers.
Data »
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 …
Generating Random Text Files for Testing
![91ebozy1e3b138waujy28agrngy[1]](https://i2.wp.com/www.krazyworks.com/wp-content/uploads/2021/08/91ebozy1e3b138waujy28agrngy1-80x80.jpg "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 …
Monitoring »
Finding Cron Jobs
![iwoau71okwxqh4jv3k4ook32qps[1]](https://i2.wp.com/www.krazyworks.com/wp-content/uploads/2021/08/iwoau71okwxqh4jv3k4ook32qps1-80x80.jpg "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
![5gtysva4wkc8mzc1k3e66vaycxx[1]](https://i1.wp.com/www.krazyworks.com/wp-content/uploads/2021/08/5gtysva4wkc8mzc1k3e66vaycxx1-80x80.jpg "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.
Networking »
Validating HTTPS Cache Peers for Squid
![sy2zeb1vp2h8itlxfbbylw0jrm0[1]](https://i0.wp.com/www.krazyworks.com/wp-content/uploads/2019/12/sy2zeb1vp2h8itlxfbbylw0jrm01-80x80.jpg "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
![Photo-2019-10-07-14-39-03_0266[1]](https://i1.wp.com/www.krazyworks.com/wp-content/uploads/2019/11/Photo-2019-10-07-14-39-03_02661-80x80.jpg "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.
Editor
Igor
Sr. Unix SysAdmin with twenty years experience supporting Solaris, HP-UX, AIX, IRIX, and Linux servers in a large distributed environment.
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