Category: Linux

How to block/restrict max number of HTTP connection per IP address

I have written a simple PHP file to do that for me and I run it every 1 minute using Cron-Job.

The script needs to run as PHP-CLI (cron or command prompt) as it runs system commands and would be blocked if run as Apache script.

Here is the code.

How to Find & replace recursively in Linux from command line script

Following is the script to find any phrase and replace it with another.

for i in `grep –include=”*\.include” -rl ‘phrase to search’ /var/www/`; do

sed –in-place=bak -e ‘s/phrase to search/phrase to replace with/g’ “$i”

done

The above script searches folder /var/www and all of its sub folders with any file with extension .include for phrase “phrase to search” and will replace all the found phrases with phrase “phrase to replace with”

How to auto start Red 5 on Ubuntu or any linux distro

Following script monitors RMTP port, which indicates if Red5 is running or not

if (netstat -na | grep -q :1935) ; then
echo “Red5 running.”
else
bash /usr/local/red5/red5.sh
fi
If RMTP is open for connection nothing is done, else the script tries to start Red5 server by executing the red5.sh startup script.
so save the above script in red5 folder say /usr/local/red5/cron.sh
now we need to add a cron job to run the cron.sh at specified intervals, e.g. we will run it every 2 mins.
edit cron jobs with following command
crontab -e
now add following line to the cron jobs
0,2,4,6,8,10,12,14,16,18,20,22,24,26,28,30,32,34,36,38,40,42,44,46,48,50,52,54,56,58,59 * * * * /usr/local/red5/cron.sh & >/dev/null 2>&1
The above setup will monitor red5 every two minute , if server is not running it will start the server.

The script whose uid is 33 is not allowed to access /tmp owned by uid 0

If SAFE MODE is on in PHP, the owner ID of the PHP file needs to be same to any folder or file it tries to access. So if you try to use sessions and if your PHP is configured to use /tmp folder for saving session data it can cause error shown in title of this blog post.

To fix it check following directive is set as follows

session.save_path = /tmp

If yes create folder

/var/lib/php5/session

change owner of the above folder to same as that of the web server, so for e.g. you would say

chown www-data:www-data /var/lib/php5/session

now change /etc/php.ini  or /etc/php5/apache2/php.ini

to use following setting

session.save_path = /var/lib/php5/session

now reload web server e.g.

service apache2 reload

or

/etc/init.d/apache reload

This should fix the problem

Mysql Replication Settings

http://www.softwareprojects.com/resources/programming/t-how-to-move-copy-a-live-mysql-database-and-what-1257.html

On Mysql Server

1. Turn binary logging on and add server id

CAUTION ! DO NOT USE “log-bin=/var/log/mysql/mysql-bin.log’

[mysqld]
log-bin=mysql-bin
server-id=1

2. Create replication account on the server

GRANT REPLICATION SLAVE ON *.* TO ‘repl’@’slave-ip-address’ IDENTIFIED BY ‘password-here’;

3. Keep the above mysql console open, start new terminal and connect to server via new terminal

cd /var/lib/mysql

now use dir, you should see all the database folders

4. Time to lock all the databases on server.

mysql> SET GLOBAL WAIT_TIMEOUT=600000; SET WAIT_TIMEOUT = 600000; FLUSH TABLES WITH READ LOCK;

now on the new console enter

root@server:/var/lib/mysql#tar -cvf /tmp/mysql-snapshot.tar ./ –exclude mysql &

enter following in mysql console, this will show the position of server in log file, keep this window open and note file and position column

SHOW MASTER STATUS;

now enter following in mysql console

UNLOCK TABLES;

5. Copy the tar file from master to slave server

scp -i permission-file.pem /tmp/mysql-snapshot.tar root@slave-server-ip:/root/

6. Extract the tar file on slave server

cd /var/lib/mysql

mv /root/mysql-snapshot.tar .

tar –extract –file=mysql-snapshot.tar

7. Change server id on slave mysql server, add following to config file /etc/my.cnf or /etc/mysql/my.cnf

[mysqld]

server-id=2

8. Start or restart Slave mysql server with

service mysql restart

9. Login to mysql console and enter

mysql>stop slave;

mysql> CHANGE MASTER TO
MASTER_HOST=’ip-of-master-server’,
MASTER_USER=’repl’,
MASTER_PASSWORD=’replication_password-from-step-2′,
MASTER_LOG_FILE=’recorded_log_file_name-from-step-4′,
MASTER_LOG_POS=recorded_log_position-from-step-4;

mysql>start slave;

If every thing is done correctly the slave should start replicating.

Once master has been set on and slave started on Slave, after restart the slave will auto start.

If something is not right on slave, login to slave mysql console

use following

stop slave;

reset slave;

now from the new bash console, reextract the tar file replacing existing file with following command

root@slave-server:/var/lib/mysql# tar –overwrite –extract –file=mysql-snapshot.tar

now repeat step 9.