SSH tunnels provide a very effective means to access remote services and applications. Not only does it provide encryption of data between hosts, but it allows you to route connections between a sequence of servers, thus chaining connections. A common use of this method is to provide encrypted connections to MySQL servers so that user accounts can be limited to only “localhost” privileges, yet accessed from remote workstations without having to run MySQL+SSL.

The concept is simple, for example let’s say you have three servers: localhost (your workstation in America), a server in Europe, and a server in Japan. You want to access Apache running on port 80 on the Japan server but because of firewall restrictions you cannot access port 80 remotely, and to make things more difficult the Japan server only allows SSH connections from the Europe server’s IP. We can solve this by creating a SSH tunnel that forwards localhost port 8080 …

A special extended edition of Tech Messages for 2011-09-21 through 2012-05-11:

• Understanding Linux CPU Load - when should you be worried?
• Performance Testing - Load Balancer SSL Stress Testing
  This is a great simple test. Thanks, Corey!
• Mosh: the mobile shell
• Twitter open sources its MySQL secret sauce
• Lab Overview
  This guy is serious about his lab!

Recent news that Microsoft and Barnes & Noble agreed to partner on the Nook e-reader line rather than keep fighting over intellectual property suggests the prospect of more settlement and fewer IP suits in the industry. However, the deal further obscures the blurry IP and patent landscape currently impacting both enterprise IT and consumer technology.

It is good to see settlement — something I’ve been calling for, while also warning against patent and IP aggression. However, this settlment comes from the one conflict in this ongoing war that was actually shedding some light on the matter, rather than further complicating it.

See the full article at TechNewsWorld.

Topics for this podcast:

*OpenStack, Amazon, Eucalyptus and Citrix engage in open cloud warfare
*Microsoft spins off new company for openness
*Updates on automation players Puppet Labs and Opscode with Chef
*Percona turns attention to MySQL high availability
*Open APIs as the fifth pillar of modern IT openness

iTunes or direct download (28:42, 4.9MB)

Installing MySQL-Frontend Chive (A phpMyAdmin Alternative)

This guide explains how to install the phpMyAdmin alternative Chive. Chive is a free, open source, web-based database management tool with easy administration, super fast UI and state of the art web technologies. It takes advantage of the capabilities of modern browsers. Features include an SQL editor with syntax highlighting and built-in profiling of SQL queries.

There are probably thousands of articles on the Internet about disk statistics in Linux, what various columns mean, how accurate the information is, and so on. I decided to attack the problem from a little bit more practical side. Hopefully this will be just the first of many future posts on identifying various I/O related performance problems on a MySQL server.

Linux exposes disk statistics through /proc/diskstats. However the contents of this file isn’t something anyone can understand quickly. It needs a tool to transform the information into something human readable. A tool that is available for any Linux distribution is called iostat and comes with sysstat package.

How to access and read I/O statistics

Usually you want to call iostat one way:

iostat -xkd <interval> <block device>

The interval should typically be one second as it is the …

You cannot use Yum to an unregistered Linux by default after installation. As a workaround, you will have to create a repo from your installation CD or ISO file.

1. Mount your DVD/CDROM. Run this command from shell.

mount /dev/cdrom /mnt


2. Or if you have no DVD/CDROM, you can copy your ISO file to the server and mount like this.

mount -o loop -t iso9660 yourisofile.iso /mnt


3. Change directory to /mnt and run this command

yum clean all


5. Edit /etc/yum.repos.d/iso.repo. Use nano or vi.

nano /etc/yum.repos.d/iso.repo


6. Paste below and save.

[local]
name=Local CD Repo
baseurl=file:///mnt
gpgcheck=1
gpgkey=file:///mnt/RPM-GPG-KEY


Now try installing using …

Have you ever spent a lot of time thinking about how to install and configure a Linux server for MySQL database? I will try to highlight all the critical steps and some of the decisions you may need to make.

Linux distribution.

Unless you have a really good experience in systems administration, choose a widely supported Linux distribution. The best choices usually are RedHat or its free cousin called CentOS. Compatible alternatives you could also consider are Scientific Linux and Oracle Linux. Make sure you will be installing a 64-bit version, unless you have a very good reason not to.

Storage.

If you have multiple disks available in the server, create a single array from all disks. Choose RAID level that offers better performance rather than more disk space, so either RAID 1 or RAID …

Here are some quick and easy bash commands to solve every day problems I run into. Comment and leave some of your own if you like. I might update this post with new ones over time. These are just some common ones.

Iterate through directory listing and remove the file extension from each file
ls -1 | while read each; do new=`echo $each |sed 's/\(.*\)\..*/\1/'` && echo $new && mv "$each" "$new"; done

Output relevant process info, and nothing else
ps axo "user,pid,ppid,%cpu,%mem,tty,stime,state,command"| grep -v "grep" | grep $your-string-here

Setup a SOCKS5 proxy on localhost port 5050, to tunnel all traffic through a destination server
ssh -N -D 5050 username@destination_server'

Setup a SOCKS5 proxy via a remote TOR connection, using local port 5050 and remote TOR port 9050
ssh -L 5050:127.0.0.1:9050 username@destination_server'

Display text or code file contents to screen but don't display any # comment lines
sed -e '/^#/d' $1 < $file_name_here …

Swapping occurs when system moves some data between memory and a special area on disk called swap space. The process is called swapping in or swapping out depending on the direction in which it happens. System swaps out when it makes a decision to free up some physical memory (RAM) and pushes data out to disk. It swaps in when an application needs to access data that was swapped out. MySQL is like any other application and any memory it holds can also be sent to disk. It may have severe negative impact on performance.

The foremost step to prevent swapping is ensuring that not database, not any other application can either independently or collectively use up all available memory. The peak usage may not exceed a threshold that still leaves comfortable buffer for any remaining system activity. If this condition is not met, nothing can help and swapping may occur.

Further tuning can be done …