just another blog

keep in mind

2011-09-09T10:58:00.000+04:00

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

analyze this

2010-11-29T15:24:00.001+03:00

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

2010-10-19T12:48:00.000+04:00

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

enable sun-java in google chrome

2010-09-17T10:47:00.002+04:00

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

2010-05-21T17:35:00.003+04:00

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

2010-03-18T14:54:00.005+03:00

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

2010-03-05T11:21:00.010+03:00

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

2009-09-10T14:52:00.003+04:00

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

2009-09-02T20:09:00.004+04:00

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

2009-08-01T14:34:00.000+04:00

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

apache fail

2009-07-31T16:49:00.001+04:00

Don't use apache2-mpm-worker for perl projects. Never!

never

NEVER! :)

nginx basic auth (htpasswd)

2009-07-22T16:37:00.007+04:00

Nginx supports basic auth (ngx_http_auth_basic_module)

directives:
auth_basic [|off]
auth_basic_user_file path/to/file

htpasswd file format:
# comment
login:password

Command htpasswd should be used with option -d , because nginx supports crypt() algorithm only.

Example:
htpasswd -c -d /etc/nginx/htpasswd asalnikov

nginx.conf part:
location /
{
auth_basic "closed site";
auth_basic_user_file /etc/nginx/htpasswd;
...
}

Kubuntu Jaunty Wi-Fi Speed with WPA2 encryption

2009-07-12T22:28:00.004+04:00

After upgrading my Kubuntu to Jaunty, I had problems with Internet access via Wi-Fi. Speed was many times less than before the upgrade (only then I use WPA2 encryption). This way solve the problem:

$ sudo aptitude install linux-image-2.6.28-11-generic

and reboot, choosing this kernel

P.S. in KDE4, NetworkManager replaced by plasma-widget-network-manager. If you can't connect to your wi-fi network with WPA2 encryption just install "linux-backports-modules-jaunty-generic" package.

ssh tunnels

2009-07-09T12:27:00.000+04:00

In many cases, development projects are on the same data center, and the server product is on the other. And often it is necessary to provide the link between the test and product servers.

Simply ssh tunnel:

ssh -p40088 -2 -N -C -f -L 172.11.5.58:3307:10.20.1.103:3306 tunnel@x.x.x.x

-p40088 - gateway to production DC ssh port
172.11.5.58:3307 - host:port on local server
10.20.1.103:3306 - host:port on remote server
tunnel@x.x.x.x - username@host of gateway to production DC

And now when I connect to port 3307 on local server I get connect with 10.20.1.103:3306 on production server.

How to copy directories structure

2009-07-06T17:20:00.002+04:00

cd olddir
find . -type d > /tmp/dirlist
cd newdir
for i in `cat /tmp/dirlist` ; do mkdir -p $i ; done

very simply :)

Nginx rewrite for user subdomains

2009-06-30T17:20:00.007+04:00

For example you need to store few userpics for each user with possibility to set default userpic. First we must determine that for static content we will use nginx as one of the fastest web server. Userpics will be stored by scheme: "files/userpics/[first two letters from username]/[username]/"
directories scheme:


root@server:~# tree files
files
`-- userpics
|-- te
|   |-- test11
|   |   |-- 0.gif
|   |   |-- 1246347162.gif
|   |   |-- 1246362446.jpg
|   |   `-- 1246363739.gif
|   `-- test44
|       |-- 0.gif
|       |-- 1246365659.gif
|       `-- 1246366597.gif
`-- tu
   |-- turkish
   |   |-- 0.gif
   |   |-- 1246357650.gif
   |   |-- 1246357669.gif
   |   `-- 1246363992.gif
   `-- tuzik
       |-- 0.jpg
       |-- 1246365938.jpg
       `-- 1246365974.jpg

Default userpic will be addressed to 0.[jpg|png|gif] (file extension depends on extension the parent file)
Http request http://test11.mydomain.com/userpics/1246347162.gif must return this file:
/opt/www/files/userpics/te/test11/1246347162.gif
if file does not exist, nginx must return default userpic for this user:
/opt/www/files/userpics/te/test11/0.[jpg|png|gif]
if default userpic does not exist, nginx return default userpic for all users "/userpic-default.png"

part of nginx.conf:


location /userpics/ {
default_type image/jpeg;
root   /opt/www;
access_log /var/log/nginx/static.access.log  main;
if ($host ~* "(..)(.*)\.mydomain\.com") {
        set $a $1;
        set $b $2;
        rewrite ^/userpics/(.*)$ /files/userpics/$a/$a$b/$1;
}
if (!-f $request_filename) {
    rewrite ^/files/userpics/(.*)$ /files/userpics/$a/$a$b/0.jpg;
}
if (!-f $request_filename) {
    rewrite ^/files/userpics/(.*)$ /files/userpics/$a/$a$b/0.gif;
}
if (!-f $request_filename) {
    rewrite ^/files/userpics/(.*)$ /files/userpics/$a/$a$b/0.png;
}

break;
error_page   404 =200   /userpic-default.png;

}

UPD Best way: don't use "if" in location level.

try_files /files/userpics/$a/$a$b/0.jpg /files/userpics/$a/$a$b/0.gif /files/userpics/$a/$a$b/0.png /userpic-default.png;

regular expressions

2009-06-25T16:21:00.000+04:00

Some tips about regular expressions:
(..) - two symbols
([0-9]{4}) - 4 numeric symbols
([a-c]+) - letters from a to c. many times as you like
(.*) - any symbols. many times as you like

A bit later I'll write about useful rewrite :)

Disable Midnight Commander tab and spaces highlighting

2009-06-22T11:48:00.000+04:00

In file ~/.mc/ini check these parameters
editor_visible_tabs = 0
editor_visible_spaces = 0
They must be equal "0"