I rarely use GUIs, but when I do, it’s from CLI and every time I run into the annoying MIT-MAGIC-COOKIE-1 data did not match error. It’s easy to fix, but it happens to me so …
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Commands & Shells »
Deleting Hidden Files
This simplest of problems just never fails to find a new victim. For whatever reason you want to delete all hidden files in the current directory and subfolders. Without much thinking you just type rm -rf .* Here’s a classic example of one developer giving another developer a terrile advise. Read the full story »
Quickly Grow tmpfs filesystem
Just a quick command to double the size of the /tmp filesystem that uses tmpfs. This is for those situations when you can’t be bothered to think.
Duck Duck Go Search from Shell
The ddgr python script is a command line interface for Duck Duck Go – a privacy-oriented search engine that, unlike Google, will not give away your data to the likes of Cambridge Analytica. In the …
Obfuscating Shell Scripts
Unix shell scripting language is run by the command-line interpreter and, as such, can be read and understood by anyone with sufficient access and experience. Sometimes this is not a good thing. Sometimes you want …
The Mystery of a Hemisphere
To make this long (and embarrassing) story short: a friend’s kid had a homework assignment in geometry to calculate the surface area of a conjoined cone, a cylinder, and a hemisphere.
Raspbian ‘partitions on different devices’ Error
After downloading a Raspbian image and writing it to an SD card, you get the following error when trying to boot the Pi: “Could not expand filesystem, please try raspi-config or rc_gui. Boot and root …
Tmux Bootstrap Configuration
Just a list of commands to quickly configure tmux with some of the best (i.e. my favorite) plugins and options. Feel free to disagree – you may be right – but I don’t think so.
Find Large Files
Every time a filesystem is running out of space and I need to find something to delete, I end up googling the syntax for the find command to make sure it stays off NFS and …
Show Logged In Users During a Time Window
Let’s say you want to see who was logged in on the server during last weekend. This includes users who, say, logged in on Thursday and haven’t logged out until Saturday afternoon.
Extracting Email Addresses from TCP Streams
Here’s a quick example of using tshark to extract email addresses from TCP streams. Let’s say some application on your server is sending emails and you want to find out who is receiving those emails.
Export WP Posts and Sync to Sharepoint
Long story short: old wiki is overloaded and broken; new wiki is not a wiki but SharePoint – a glorified file server; people are forced to improvise and put documentation on a WP wiki; bosses …
Useful MySQL One-Liners
I am by no means an expert SQL programmer. Having said that, I’ve been using MySQL for a very long time. This is a collection of simple but useful SQL queries and MySQL configuration options. …
Plotting Log Data
While I am on the subject of selecting time ranges from logs, a practical application presented itself. A lonely server in a far-away land with a habit of running out of memory could only be …
Croncal – the Cron Calendar
The croncal is a clever Perl script that reads entries in your crontab and outputs a schedule, showing the time when cron jobs will run.
Install and Configure Etckeeper
Etckeeper is a handy tool that uses git to keep track of changes to anything in /etc (or any other folder you choose). It’s very simple to use and can help you quickly identify and undo stupid …
Using IPTables to Allow Access to Private Networks
Below is a quick example of how to use iptables to allow port access for all types of private networks. In this case we’re allowing access to ports 10000 and 20000, commonly used by webmin and usermin.
Get a List of all ESX Hosts in a Datacenter
Another simple one-liner to get a list of hostnames of all ESX servers in the vCenter. This can be useful for a number of things, specifically as input for other PowerCLI scripts.
Use PowerCLI to Change NIC Type
This is a quick PowerCLI script that reads from a list of VM names and for each VM with network adapter type “E1000” changes it to “Vmxnet3”. Nothing fancy, no reboot is needed. MAC should …
Pushing SSH Keys
This is just a quick note for me on pushing SSH keys using sshpass and xargs. The ~/hosts.txt file contains a list of remote hosts, one per line. And the ~/.passwd.txt contains your password. Make sure to chmod 400 …
Configure and Run esxcli on Red Hat
The esxcli utility is used to interface with the vSphere and ESX hosts. It is a useful tool for getting to some basic VMWare functionality from Unix shell. It is also a pre-requisite for some of …
Wget Examples
This is a follow-up to my previous wget notes (1, 2, 3, 4). From time to time I find myself googling wget syntax even though I think I’ve used every option of this excellent utility over the …
Samba Flexible Character Mapping
This is probably old news to most of you, but I just found out: Samba v 3.5+ has a new option for flexible mapping of filename characters. Unix filenames allow certain characters that Windows filename …
Install Webmin on CentOS and Redhat
Just a quick short-hand to installing Webmin on CentOS/RHEL. The latest Webmin version comes with a cool new interface theme. You should check it out.
Commands & Shells »
Verify Network Port Access
There are several tools you can use to verify access to a remote network port: nc, tcping, telnet. Unfortunately, nc from the netcat package has been replaced by the one from nmap, which lacks the -z option, making …
Document Conversion with Unoconv
The other day I ran into the “Flexible Import/Export” article by Bruce Byfield in the March 2018 issue of Linux Pro Magazine and thought it could use some more detail. So here’s some more detail.
Applications »
Late Night Rant: Agile
CollabNet VersionOne has released it’s 12th annual “State of Agile” report. The survey involved more than 1,400 software professionals in various roles and industries over the fourth quarter of 2017.
Only 12% responded that their organizations …
SystemD: Back To The Future
A creature in its death throes, Sun Microsystems gave birth to Solaris SMF – the product of a disturbing union between Unix System V and the Microsoft Windows Registry. Shortly thereafter the proud father died, …
Data »
Document Conversion with Unoconv
The other day I ran into the “Flexible Import/Export” article by Bruce Byfield in the March 2018 issue of Linux Pro Magazine and thought it could use some more detail. So here’s some more detail.
Encrypted Volumes and Portable Apps
This is a description of an uncomplicated setup for an encrypted volume and portable applications for a Windows laptop consisting of a USB3 storage device, VeraCrypt OSS OTFE, a hardware password wallet, and portableapps.com software.
Monitoring »
CLI System Monitoring Tools
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
I have an FTPS server running VSFTP and below is collection of commands useful for monitoring activity and analyzing the logs.
Networking »
Verify Network Port Access
There are several tools you can use to verify access to a remote network port: nc, tcping, telnet. Unfortunately, nc from the netcat package has been replaced by the one from nmap, which lacks the -z option, making …
Detect SSL Certificate Injection
When the SSL Digital Certificate is intercepted and replaced by a device between your browser and the Web site, we call it certificate injection. This method is more commonly used not by hackers, but by …
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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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