Shows the controls, indicators, and connectors located on the system’s back panel.

I have seen many pages illustrating how to cause a kernel panic. Some have some short (relative to others) programs to do this. Honestly you can cause a kernel panic with the magic sysrq commands. For those that missed my earlier article, you can find it at Magic Sysrq.

In this situation, we will need to enable the sysrq:

echo 1 > /proc/sys/kernel/sysrq

Then issue the kernel panic.

echo c > /proc/sysrq-trigger

This causes a kexec reboot with a crashdump. If you have more information on this process, please let me know.

I think it is a good idea to ensure that one does not fall victim to phishing scams.

To this end, Open DNS has posted a phishing quiz. I only got 12 out of 14 correct, but the two I got wrong, I erred on the side of caution and marked them as phishing scams when they were legitimate links. And honestly, I do not use those services so I could not honestly say what their domains are.

Think you can outsmart Internet scammers?

This was a question posed to me today. The short answer is ‘no’.

Luckily, the Percona group was kind enough to do the benchmarks on performance logging. You can find more information here:

Impact of logging on MySQL’s performance

Google has announced the end of their on-line collaboration tool, Google Wave. Having obtained a beta invitation, I tested out the tool and found that, while the concept was promising, the usefulness was lacking. The fact they tried to market it as an e-mail replacement was a bit annoying. While email does have its problem, the basic protocol for mail will be hard to replace.  This announcement comes on the heels of Google announce they would also stop production on Google Buzz. Personally, it seems Google was trying to be first in creating the next big thing. And while they tried to generate a lot of Buzz, I think it is time to Wave goodbye to these apps.

In order to have multiple people able to update the same directories/files:

1. Create directory that multiple user to access.

# mkdir /var/www/html/site1.com

2. Create the group that needs to be able to write to the directory.

# groupadd webdev

3. Change the group associated with the directory.

# chgrp webdev /var/www/html/site1.com

4. Make the directory group writable.

# chmod g+w /var/www/html/site1.com

5. Change the SGID of directory so that any new files retain the group ownership

# chmod g+s /var/www/html/site1.com

6. Create the new user, adding the additional group(set the home directory if necassary).

# useradd -G webdev -d /var/www/html/site1.com user1

7. Change the umask so that newly uploaded files retain group writable permissions:

# vi /etc/ssh/sshd_config

Update the sftp subsytem line to look like so:

Subsystem sftp /bin/sh -c ‘umask 0002; /usr/libexec/openssh/sftp-server’

For chrooted sftp:

Subsystem sftp /bin/sh -c ‘umask 0002; internal-sftp’

Note: if you are trying to make these changes to a directory structure that already exists, any changes to permissions will need to be done recursively.

Last night saw a DNS pandemic in server failures. The following clip comes from ISC’s website:

I suffered from this last night, instead of trouble shooting, I just went to bed and let my ISP handle it.

Further Reading:

• https://www.isc.org/software/bind/advisories/cve-2011-tbd
• http://wpengine.wordpress.com/2011/11/15/our-issues-are-actually-internet-wide-dns-failures-in-america/

I received an update on the worlds migration on IPv6 and thought I may share:

* IPv6 Deployment Growth

Of the 39,570 networks in the world running BGP, the number
running IPv6 has increased to 4,830, or 12.2%. This is an
increase from 7.4% just one year ago or 9.5% six months back.

The global IPv6 routing table has passed 7000 IPv6 prefixes.

Source: http://bgp.he.net/ipv6-progress-report.cgi

Further reading

• http://ipv6.he.net/certification/

We were discussing clearing out swap today so I came up with this quick one-liner to clear out swap:

# free -m | grep -i swap; sudo swapoff -a && sudo swapon -a; free -m | grep -i swap

Swap:        5887         49       5838

Swap:         5887          0       5887

One caveat though, you may want to verify that there is enough memory available to free up swap. Likely the items in swap are old and you will not need it, but no sense having your server run out of memory unnecessarily.

Often times replication gets hosed and you have to skip a bad record. It’s easy to use:

mysql> SET GLOBAL SQL_SLAVE_SKIP_COUNTER = 1;

But what if you have an undetermined number due an upgrade of mysql? Luckily Maatkit has a nice little script that will increment skip counter by one until it no longer sees an error. Simply grab the perl script and run it as so:

# wget http://maatkit.org/get/mk-slave-restart

# perl mk-slave-restart –verbose

Once the errors are done, you can ctrl-c out of the script and check the slave status.

• http://www.maatkit.org/