LinuxWebLog.com

Great step by step explanation of investigating file lock contentions, specifically when dealing with php and sessions.

The upcoming version of OpenSSH (4.8p1 for the GNU/Linux port) features a new configuration option : ChrootDirectory. This has been made possible by a new SFTP subsystem statically linked to sshd.

As developers get started with a project, they prefer having total control over the development environment, as much as possible to perfectly match the deployment environment. The other strong requirement, especially in a team with mutiple developers would be to work on exactly replicated environments.

When developers shift from PHP, Ruby or any other platform to Python, the very first road block they face (most often) is a lack of an overall understanding of the Python ecosystem. Developers often yearn for a tutorial or resource that explains how to accomplish most tasks in a more or less standard way.

What follows is an extract from the internal wiki at my workplace, which documents the basics of the Python ecosystem for web application development for our interns, trainees and experienced developers who shift to Python from other platforms.

So, you have a binlog. You want to find out something specific that happened inside of it. What to do? mysqlbinlog has some neat features, which I thought we would look at here.

I should first explain what mysqlbinlog really is. It is a tool that lets you analyze and view the binlogs/relaylogs from mysql, which are stored in binary format. This tool converts them to plaintext, so that they’re human-readable.

Here are notes I've found useful for configuring reliable shared disk on a linux cluster...

This Sendmail error--also seen as "Transient parse error -- message queued for future delivery" or "Name server: domain: host not found"--indicates that Sendmail encountered a problem with one of its DNS resource record lookups of the destination domain.

The grub bootloader is particularly useful, especially when upgrading and testing new kernels. I recently found a way to modifiy the default boot config to make it useful when you wish to remotely upgrade a kernel and boot into it once only without being at the console to change the default back.

The stub_status module provides the ability to get some stats from nginx...

active connections -- number of all open connections including connections to backends

server accepts handled requests -- nginx accepted connections, handled connections (no one was closed just it was accepted), and handles requests (requests per connection = handles requests / handled connections)

reading -- nginx reads request header

writing -- nginx reads request body, processes request, or writes response to a client

waiting -- keep-alive connections, actually it is (active - reading + writing)

Whenever sendmail has to deliver mails to other hosts which cannot be reached at that time, the messages are kept in the queue. Although the other hosts could be reached again and you want to tell sendmail to flush the mail queue, the command

sendmail -q -v

does not really try to reconnect to these hosts and still assumes that the connection timed out. The reason is that the hoststatus is cached, per default for a period of 30 minutes. Using

sendmail -OTimeout.hoststatus=0m -q -v

you can re-run the mail queue and force sendmail to reconnect to the hosts.