![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 »RHEL/CentOS Yum Operations
The Yellowdog Updater, Modified has more features than most of us will ever need. Below are some hopefully useful examples that will help keep your system maybe secure by replacing old known bugs with new …
VSFTPd, SSL, and Firewalls
If you ever wanted to configure SSL/TLS encryption for an FTP server behind a firewall, the “Google wisdom” ranges from “a major pain” to “can’t be done”. Fortunately, things are not all that bad. In …
Using Pflogsumm Postfix Log Analyzer
Pflogsumm is an oldie but a goodie. It’s a Perl script that sifts through your Postfix server maillog and provides you with a neat summary of events and some statistics. This information can be useful …
Visualizing Apache Logs with Logstalgia
The Logstalgia is a cool graphical utility for visualizing the Apache access_log files. The practical value of Logstalgia is debatable, but it’s entertainment value is not in question. The managers and NOC operators can stare …
Sending Attachments Using Mailx
Sometimes it’s just better to attach a file to your email than to “cat” the contents into the email body. Later versions of mailx support the “-a” option for handling attachments. With the older mailx …
Fail2ban Whitelist IPs
Fail2ban is an excellent security tool that will do a good job safeguarding your server. However, using fail2ban you may run into two issues: friendly fire and inability to permanently ban hostile networks. I already …
Identifying Available IPs on the Network
At some point available IPs on your network may become few and hard to come by. Documentation becomes outdated and does not accurately reflect which IPs are still in use. A good starting point would …
Multithreaded Encryption and Compression
One problem with encryption is it’s a slow and resource-intensive process. While most encryption software lacks multithreading support, it is possible to use the GNU Parallel to take full advantage of modern multi-core CPUs to …
Using truss and nawk to Trace Solaris Processes
Here’s the problem I ran into today on a Solaris 11 SPARC server: an application UI would occasionally freeze for a few second when executing a particular function. Nobody could quite figure out where the …
Filesystem Syncronization with Lsyncd
Lsyncd monitors a local filesystem for changes and mirrors those changes to a filesystem on a remote server. The advantage of lsyncd over rsync is the former’s ability to detect filesystem changes without having to re-scan …
Toilet Fun
It’s been a slow Friday afternoon at the office, so I decided to pimp my VM. The tool of choice is “toilet“. Depending on your flavor, this may or may not be easy to install. …
Resizing Hitachi VSP LDEVs (LUNs)
Resizing Hitachi VSP LUNs (aka LDEVs) is a quick and simple task. Unfortunately, due to Hitachi Storage Navigator’s archaic design, the LDEV resize function, while easy to use, is not easy to find. So, here’s …
Adding Swap with Solaris 11 ZFS
With the swap partition residing on a ZFS filesystem, you have an easy way of adding swap on the fly. Reducing swap is not quite so simple, but we’l talk about that later. To check …
Rescanning New LUNs on VNX
Just a quick background of the little problem I ran into with our VNX: after creating a couple of LUNs for the mapped file pool using Unisphere, I clicked “Rescan Storage Systems” and got “This …
Enable NTP Client on Solaris 11
Just some quick instructions for configuring and enabling NTP client on Solaris 11.
Remove Duplicate IPTables Rules
Duplicate entries may appear in your iptables configuration due to parallel efforts of various network security-related applications that may be running on your server. In most cases, having duplicate iptables rules is no big deal, …
Block WordPress Attackers With IPTables
After installing LogStash, I noticed server load went from around 1.2 to 50+. This was cause by a brute-force attack against WordPress wp-login.php from some IP in France (of all places). While LogStash should not …
Patching Binary Files in Bash
Just the other day I ran into a particularly annoying issue: after an application upgrade, all printed documents had “<<bbj>>~D” on the first line. The application sends EPS files to the CUPS print server. For whatever reason, …
CUPS Printing to a File
Using CUPS to print to a file instead of an actual printer is a great idea for troubleshooting and archiving purposes. This saves trees but, most importantly, saves you the walk to the printer. So, how …
PHP Unable to allocate memory for pool
The following error may be found in /var/log/httpd/${domain}/error_log when APC memory is set too low: “PHP Warning: require_once(): Unable to allocate memory for pool”. APC is Alternative PHP Cache. You can check the version of …
Getting Epoch Time on Solaris 10 and Older
You can get the epoch time on Solaris 11 and Linux simply by running the date command:
Quick Setup of Salt on CentOS/RHEL
Just some quick notes on installing and configuring Salt master server and minions to run remote commands for various sysamdin needs.
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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