Megalinux

Compiling Varnish/Varnishtop: Issue with do_curses

admin — Mon, 29 Nov 2010 15:20:42 +0000

When compiling varnishtop (and other tools) on RHEL/CentOS 5, I came across the following issue:
varnishtop.o: In function `do_curses': /tmp/varnish-2.1.4/bin/varnishtop/varnishtop.c:223: undefined reference to `initscr' /tmp/varnish-2.1.4/bin/varnishtop/varnishtop.c:224: undefined reference to `raw' /tmp/varnish-2.1.4/bin/varnishtop/varnishtop.c:225: undefined reference to `noecho' /tmp/varnish-2.1.4/bin/varnishtop/varnishtop.c:226: undefined reference to `nonl' /tmp/varnish-2.1.4/bin/varnishtop/varnishtop.c:227: undefined reference to `stdscr' ...... ...... collect2: ld returned 1 exit status make: *** [varnishtop] Error 1

The issue seems to be with the ncurses library that comes with the standard distribution. So, I installed the ncurses-5.7 libs from source, using:
./configure --with-shared --with-debug --enable-overwrite --with-termlib

and then recompiling/building varnish/varnishtop.

CPU/Processor information in Linux

admin — Mon, 26 Jul 2010 01:04:13 +0000

Finding Physical Processors:
$ grep 'physical id' /proc/cpuinfo | sort | uniq | wc -l

Finding Virtual Processors
$ grep ^processor /proc/cpuinfo | wc -l

Finding CPU cores
$ grep 'cpu cores' /proc/cpuinfo

“2″ indicates the two physical processors are dual-core, resulting in 4 virtual processors.
If “1″ was returned, the two physical processors are single-core.

If the processors are single-core, and the number of virtual processors is greater than the number of physical processors, the CPUs are using hyper-threading.

Finding CPU Arch
$ grep flags /proc/cpuinfo | uniq | egrep -o -w "rm|tm|lm"

Under “Flags” section in /proc/cpuinfo, you will find any of the flags “tm” or
“rm” or “lm”

rm (Real Mode) means it is a 16 bit processor
tm (Transparent Mode) means it is a 32 bit processor
lm (Long Mode) means it is a 64 bit processor

Redirecting non-www requests to www using rewriterule

admin — Mon, 26 Jul 2010 00:13:57 +0000

RewriteEngine on RewriteCond %{HTTP_HOST} !^www.your_domain.com$ RewriteRule ^(.*)$ http://www.your_domain.com/$1 [R=301]

Piwik Mediawiki Extension

admin — Fri, 11 Dec 2009 19:58:40 +0000

Piwik(http://piwik.org/) is open source self-hostable web analytics tool (like omniture or google analytics). To integrate piwik with mediawiki, I customized the existing Google Analytics mediawiki plugin (http://www.mediawiki.org/wiki/Extension:Google_Analytics_Integration) to work with piwik. To include the extension in your wiki,
unzip the file, and deploy the piwik.php extension file into WIKI_INSTALL_DIR/extensions/. Then include the file in your LocalSettings.php, using:
require_once("extensions/piwik.php");

Download piwik extension

Solution: received end packet from server, apparent master shutdown

admin — Thu, 23 Jul 2009 20:51:42 +0000

If you are getting the below error in your mysql (slave) logs:
090723 21:46:40 [Note] Slave: received end packet from server, apparent master shutdown: 090723 21:46:40 [Note] Slave I/O thread: Failed reading log event, reconnecting to retry, log 'mysql-bin.000012' at postion 106

Then, it means the slave is sharing an ID with another slave/node in the replication setup. Check the server ID to make sure it is unique.

Solution: Dell XPS M1530 Ubuntu 8.10 System Freeze Issue

admin — Fri, 24 Apr 2009 16:35:32 +0000

When using Ubuntu 8.10 and connecting to a Wireless-n (802.11n) network, the system freezes with kernel panic (as indicated by blinking scroll and numlock). The system gets unusable and you would have to reboot. I have had this issue with my Dell XPS M1530, when connecting to Apple Extreme router.

The issue with the intel wireless module driver, and will get fixed by installing the compat-wireless driver.

Try compiling this iwlagn module, http://www.orbit-lab.org/kernel/compat-wireless-2.6/2008/10/compat-wireless-2008-10-01.tar.bz2 .
Extract the archive and then follow these steps:

sudo apt-get install build-essential
cd compat*
make
sudo make install

Reboot the system, and you will not longer face kernel panic or system freeze.

UPDATE:

When installing 9.04, I figured out that 802.11N drivers for Ubuntu are totally broken. Since I did not want to fiddle around much, I added the following lines to /etc/modprobe.d/options(and restart the system):

options iwlagn 11n_disable=1

This would prevent Wireless-N mode, but it will get your Dell M1530 (and M1330) working on Wireless with Ubuntu

Using iTerm with Elasticfox on OS X

admin — Sat, 07 Feb 2009 21:55:07 +0000

Elasticfox plugin for firefox on OS X uses Terminal.app by default(to SSH into the EC2 instances). If you would like to use iTerm instead of Terminal.app:

1. Create a script (say ec2-ssh.osascript) in your home directory. This is an applescript.

on run argv
  tell application "iTerm"
    activate
    set cmd to "ssh -i " & item 1 of argv & " " & item 2 of argv
    set myterm to the last terminal
    tell myterm
      launch session "Default Session"
      tell the last session
        write text the cmd
      end tell
    end tell
  end tell
end run

2. Edit ElasticFox properties. It should look like the following:

So, every time you try to SSH, it would use iTerm instead of Terminal.app

Using Tcpdump for MySQL query logging

admin — Mon, 24 Nov 2008 19:54:54 +0000

If you are a privileged user (i.e. root), you can use tcpdump on a database server to take a peek into a network stream and filter for packets that go to MySQL. Those packets contain queries. Here’s a quick one-liner :
# tcpdump -i eth0 -s 0 -l -w - dst port 3306 | strings | perl -e ' while(<>) { chomp; next if /^[^ ]+[ ]*$/; if(/^(SELECT|UPDATE|DELETE|INSERT|SET|COMMIT|ROLLBACK|CREATE|DROP|ALTER)/i) { if (defined $q) { print "$qn"; } $q=$_; } else { $_ =~ s/^[ t]+//; $q.=" $_"; } }'

Thanks to: http://www.mysqlperformanceblog.com/2008/11/07/poor-mans-query-logging/

mod_fcgid: can’t apply process slot

admin — Tue, 23 Sep 2008 12:11:22 +0000

It turns out that FastCGI (and I think both for mod_fastcgi and mod_fcgid) doesn’t play well with many of the default Linux setups. fcgid sets up a directory in /var/log/httpd/fcgidsock (mod_fastcgi may be a slightly different directory). The problem is not that the permissions are wrong, but that the permissions of the parent directory are wrong. More to the point, the permissions of the parent directory are made for standard Linux security purposes, not for the purposes of running FastCGI.

The fix is simple. In my case it was a simple chmod 755 /var/log/httpd, which allows Apache to actually read its log directory! Before the change, I was getting “Service Unavailable” with a log error of [warn] mod_fcgid: can’t apply process slot for [dispatch.fcgi full path]. Now it works!

Screenshot Shortcuts in Mac OS X

admin — Tue, 15 Jul 2008 09:27:54 +0000

Command-Shift-3: Take a screenshot of the screen, and save it as a file on the desktop

Command-Shift-4, then select an area: Take a screenshot of an area and save it as a file on the desktop

Command-Shift-4, then space, then click a window: Take a screenshot of a window and save it as a file on the desktop

Command-Control-Shift-3: Take a screenshot of the screen, and save it to the clipboard

Command-Control-Shift-4, then select an area: Take a screenshot of an area and save it to the clipboard

Command-Control-Shift-4, then space, then click a window: Take a screenshot of a window and save it to the clipboard