Turning on bind query logging

If you want to turn on the query logging for bind, you can use the rndc command.

$ rndc querylog

To see whether your querylog is on or off, use this below command:

$ rndc status
or
$ /etc/init.d/named status

After running the above command, you can see these lines:

[root@secondary-dns ~]# rndc status
number of zones: 5
debug level: 0
xfers running: 0
xfers deferred: 0
soa queries in progress: 0
query logging is ON
recursive clients: 0/1000
tcp clients: 0/100
server is up and running

Converting flv files to avi and mpeg

In linux we have a good tool, although text based, to convert between various video format. The tool is ffmpeg. This article will guide you on how you can convert flv format video to avi and mpg.

1. change your directory to the directory where your flv video is located.

2. run ffmpeg command:
$ ffmpeg -i input.flv output.avi
where -i stands for input and output.avi is the output file in avi or mpg.

3. For more advanced setting, you can use the command below
$ ffmpeg -i input.flv -ab 56 -ar 22050 -b 500 -s 320x240 output.mpg
where -ab is audio bitrate with default of 64kbps
-ar is audio samplerate with default of 44100Hz
-b is video bitrate with delault of 2000kbps
-s is size with default of 160x128px

Resetting mysql root password

Sometimes you have to access a mysql database and you somehow does not know the password or the user of the database. The last resort is you have to use the root password but the password is unknown. There is always the way to solve anything and the way to reset the root password is described below. Enjoy!

1. Open a terminal and stop mysqld daemon if it has been started: $ /etc/init.d/mysqld stop
2. Type this command: $ mysqld_safe --skip-grant-tables
3. Open a new terminal, and access mysql database using root:
$ mysql -u root mysql
4. Change root password to new password: mysql> update user set password=password('newpassword') where user='root';
5. flush mysql privileges: mysql> flush privileges;
6. Exit mysql: mysql> exit
7. Close the terminal with the mysqld_safe command
8. Restart mysql: $ /etc/init.d/mysqld start

Setting up your own ntp server

NTP or network time protocol is a protocol that will synchronize the time of a computer client or server to another server or reference time source, such as a radio or satellite receiver or modem. Typical NTP configurations utilize multiple redundant servers and diverse network paths in order to achieve high accuracy and reliability.
Follow the below setup to install your ntp server:

1. install ntp: $ yum install -y ntp

2. edit ntp.conf: $ vi /etc/ntp.conf
example of ntp.conf:
# Permit time synchronization with our time source, but do not
# permit the source to query or modify the service on this system.
restrict default kod nomodify notrap nopeer noquery
restrict -6 default kod nomodify notrap nopeer noquery

# Permit all access over the loopback interface. This could
# be tightened as well, but to do so would effect some of
# the administrative functions.
restrict 127.0.0.1
restrict -6 ::1

# Hosts on local network are less restricted.
#restrict 192.168.1.0 mask 255.255.255.0 nomodify notrap

# Use public servers from the pool.ntp.org project.
# Please consider joining the pool (http://www.pool.ntp.org/join.html).
#server 0.rhel.pool.ntp.org
#server 1.rhel.pool.ntp.org
#server 2.rhel.pool.ntp.org
#server mst.sirim.my prefer
#server my.pool.ntp.org

#broadcast 192.168.1.255 key 42 # broadcast server
#broadcastclient # broadcast client
#broadcast 224.0.1.1 key 42 # multicast server
#multicastclient 224.0.1.1 # multicast client
#manycastserver 239.255.254.254 # manycast server
#manycastclient 239.255.254.254 key 42 # manycast client

# Undisciplined Local Clock. This is a fake driver intended for backup
# and when no outside source of synchronized time is available.
#server mst.sirim.my prefer
#server my.pool.ntp.org

# Drift file. Put this in a directory which the daemon can write to.
# No symbolic links allowed, either, since the daemon updates the file
# by creating a temporary in the same directory and then rename()'ing
# it to the file.
driftfile /var/lib/ntp/drift

# Key file containing the keys and key identifiers used when operating
# with symmetric key cryptography.
keys /etc/ntp/keys

# Specify the key identifiers which are trusted.
#trustedkey 4 8 42

# Specify the key identifier to use with the ntpdc utility.
#requestkey 8

# Specify the key identifier to use with the ntpq utility.
#controlkey 8

3. If the server you are setting up do not have internet connection, you can synchronize it with the local time of the server itself. Just comment the server part, and change it to 127.127.1.0. The sratum level is for determining what level this time server is set up for. Stratum 0 usually refers to real clock, for example atomic (cesium, rubidium) clocks or GPS clocks or other radio clocks. Stratum 1 is the machine connected to stratum 0 devices.

#server mst.sirim.my prefer
#server my.pool.ntp.org
server 127.127.1.0
fudge 127.127.1.0 stratum 10

4. synchronize the server's time with the ntp server: $ ntpdate -du mst.sirim.my

5. start ntp service: $ /etc/init.d/ntpd start

In the client machine, just type: $ ntpdate -du ntpservername. You can also put this command in crontab for the client to be update frequently

Installing lighttpd in Centos 5 for x86_64

Lighttpd is a fast and optimized web server that prioritize performance. To install this web server application, some additional work need to be done because there is no rpm compiled version of this web server for x86_64 architecture yet. So we have to do the hard work by getting the spec file, compiling the source and all. Steps to be taken to successfully install lighttpd on Centos 5 x86_64 machine are as below:

1. get the rpm source file for lighttpd from here
2. install the requirement needed to compile the source: pcre-devel 6.6-1.1, mysql-devel 5.0.22-2.1 and lua-devel. The first two can be be installed from yum: $ yum install -y pcre-devel mysql-devel. The last one can be downloaded from here and its dependencies can downloaded from here. Install the last dependencies using: $ rpm -Uvh lua-5.1.2-1.el5.kb.x86_64.rpm lua-devel-5.1.2-1.el5.kb.x86_64.rpm
3. Install the lighttpd rpm source file: $ rpm -Uvh lighttpd-1.4.16-1.el5.src.rpm
4. The spec file for lighttpd will be saved into /usr/src/redhat/SPECS
5. Compile the spec file: $ rpmbuild -bb /usr/src/redhat/SPECS/lighttpd.spec
6. The rpm for lighttpd will be saved into /usr/src/redhat/RPMS/x86_64. Install lighttpd: $ rpm -Uvh /usr/src/redhat/RPMS/x86_64/lighttpd-1.4.16-1.x86_64.rpm
7. Check whether your lighttpd has been installed: $ rpm -qa | grep lighttpd If the result is as picture, your lighttpd is installed