Inspired from a post by Concepcion Claudio Certad, today I’ve taken a look at a command that I did not known: compgen.
The compgen builtin command expands a list of arguments to generate completion matches, so it allows us to display the commands, functions, directories and aliases available for the current user. In short compgen is a command that displays commands.
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Sometimes you have some firewall that don’t allows you to accept connection other than some specific ports let’s say that you can connect on your VPS or remote server only on the ports 80 (http) and 443 (https), but you need a port also for ssh to manage your vps/server but the port 443 is used by your Web server with its https protocol, so what can you do ?
This is where sslh comes in. It’s a really simple tool that wraps incoming connections to a port and then depending on protocol redirects it onto sshd back on port 22, or to your web server on localhost:443.
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Original article by http://janssenlima.blogspot.it/ in Portuguese
Today I’ll talk about a very important type of monitoring that is rarely discussed (perhaps because not so many people are privileged to work with hardware that supports this technology: IPMI).
The Intelligent Platform Management Interface (IPMI) is a standard used to manage a computer system and monitor its operation. Its development was led by Intel and is today supported by more than 200 hardware manufacturers.
Its operation is independent of an operating system, which allows administrators to remotely manage the hardware resources even before any OS starts. For example, we can monitor through IPMI system temperatures, voltages, fans (FAN), power supplies, chassis intrusion, etc..
For the ones that wants to go deeper in IPMI specifics, I suggest reading the website of Intel . I think the most interested in this are the Data Center Managers and System Administrators of sites that must be highly available. An IPMI interface collects information using sensors that are responsible for providing this information in real-time.
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If you are a system administrator and you want to push the performance of your PHP website such as Drupal, WordPress or wrote by you or other programmers, there are good chances that you’ve heard about the Alternate PHP Cache or simply APC.
The Alternative PHP Cache (APC) is a free and open opcode cache for PHP. Its goal is to provide a free, open, and robust framework for caching and optimizing PHP intermediate code.
That everything you’ll read about APC on the php.net site, and i think is not enough in comparison to the huge boost of performance that this small component can give you, for some quick facts check the tests done by Guillermo Garron on his website.
I just realized that I’ve never written anything about one of my favorite commands on the Linux shell: locate.
This command take as input the name (or part of it) and instantly it gives you all the locations where that file is located, an alternative to this could be to use the command find, but there is an huge difference in the time that takes find to search large file systems in comparison to a locate, this difference is given from the fact that locate uses his own database where it stores all the file names, while find scan the directory and looks for the file name you have given as input.
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