keep in mind

find ./ -name config.php | while read i; do perl -i -ple 's/dodfdfdfsss44/ksfh7sfhlhs8/g' $i ; done

analyze this

my favorite log analyze tool

cat /var/log/apache2/access.log.1 |grep '" 200' | awk '{print $7}' |sort| uniq -c |sort -rn |more

my ip from command line

wget -q -O - checkip.dyndns.org|sed -e 's/.*Current IP Address: //' -e 's/<.*$//'

enable sun-java in google chrome

1. cd /opt

2. Go to http://java.sun.com/javase/downloads/index.jsp and download Java JDK 6

3. sudo sh jdk-6u21-linux-i586.bin

4. ln -sf /opt/jdk1.6.0_21/jre/lib/i386/libnpjp2.so /opt/google/chrome/plugins/

5. restart your google chrome

6. go to chrome://plugins/ webpage and check "Java(TM) Plug-in 1.6.0_21"

nginx core dump backtrace

add strings to nginx.conf

worker_rlimit_core 500m;
working_directory /path/to/corefiles;

restart nginx.

Follow to /path/to/corefiles and wait for segfault :)

then gdb /path/to/nginx /path/to/core

inside gdb input bt

ext4 disable journal

At one high loaded web project I needed a very fast file system. I decided to use Ext4 with disabled journal (As a google:))).

# Create ext4 fs on /dev/sda10 disk
mkfs.ext4 /dev/sda10

# Enable writeback mode. This mode will typically provide the best ext4 performance.
tune2fs -o journal_data_writeback /dev/sda10

# Delete has_journal option
tune2fs -O ^has_journal /dev/sda10

# Required fsck
e2fsck -f /dev/sda10

# Check fs options
dumpe2fs /dev/sda10 |more

For more performance add fstab opions: data=writeback,noatime,nodiratime
i.e:
/dev/sda10 /opt ext4 defaults,data=writeback,noatime,nodiratime 0 0

Tested at non-boot partition ;)

Key-Value Storages

memcached - distributed memory object caching system ( http://memcached.org/ )
memcachedb - distributed key-value storage ( http://memcachedb.org/ )
redis - A persistent key-value database with built-in net interface written in ANSI-C for Posix systems ( http://code.google.com/p/redis/ )
MongoDB - scalable, high-performance, open source, schema-free, document-oriented database. Written in C++ ( http://www.mongodb.org )
CouchDB - doc. oriented, written in Erlang ( http://couchdb.apache.org/ )

Riak - NoSQL, decentralized ( http://riak.basho.com/ )

RINGO - distributed key-value storage for immutable data, written in Erlang ( http://github.com/tuulos/ringo )

Dynamo - Amazon’s Highly Available Key-value Store ( http://www.allthingsdistributed.com/2007/10/amazons_dynamo.html )

Cassandra - highly scalable, eventually consistent, distributed, structured key-value store. "Dynamo 2.0" ( http://incubator.apache.org/cassandra/ )

Scalaris - scalable, transactional, distributed key-value store ( http://code.google.com/p/scalaris/ )

P.S. Storages overview from Richard Jones http://www.metabrew.com/article/anti-rdbms-a-list-of-distributed-key-value-stores

CentOS 5.2 - Missing Dependency: kernel-headers

If you have troubles with kernel-headers in CentOS 5.2 like:
Error: Missing Dependency: kernel-headers is needed by package glibc-headers
Error: Missing Dependency: kernel-headers >= 2.2.1 is needed by package glibc-headers

install kernel headers:
#uname -a
Linux myserver 2.6.18-92.1.18.el5 #1 SMP Wed Nov 12 09:19:49 EST 2008 x86_64

for x86_64
#wget http://vault.centos.org/5.2/os/x86_64/CentOS/kernel-headers-2.6.18-92.el5.x86_64.rpm
#rpm -i kernel-headers-2.6.18-92.el5.x86_64.rpm

for i386
#wget http://vault.centos.org/5.2/os/i386/CentOS/kernel-headers-2.6.18-92.el5.i386.rpm
#rpm -i kernel-headers-2.6.18-92.el5.i386.rpm

Enable mysql replication on production server

How to add slave mysql server without stopping master?

Bin-logging must be enabled on master. Then just dump all data from master:

mysqldump  --defaults-file=/etc/mysql/debian.cnf -BA --master-data | gzip > /pathtogzipfile/filename

This command dump all data from master and store master "binlog filename" and log position.

Copy gzipped dump to slave. Ungzip and apply (mysql < yourfile.sql). Execute "slave start;" (slave must be configured for replication before this step :)

keep in mind

#echo "1 2 3 4 5 6 7" |awk '{print $3, $NF}'
3 7