Install mysql-server package on master and slave.

yum -y install mysql-server
service mysqld start
chkconfig mysqld on

Now we have mysql server running on both servers.

Prepare the master server.

Edit /etc/my.cnf and add two lines in [mysqld] section
log-bin=mysql-bin
server-id=1

Restart the mysqld service, create a user for replication  and lock the tables so that slave can be configured.

service mysqld restart
mysql -u root
mysql> create user 'repl'@'%' identified by 'pass123';
Query OK, 0 rows affected (0.00 sec)
mysql> grant replication slave on *.* to 'repl'@'%' ;
Query OK, 0 rows affected (0.00 sec)
mysql> flush privileges ;
Query OK, 0 rows affected (0.00 sec)
mysql> flush tables with read lock ;
Query OK, 0 rows affected (0.00 sec)

Keep the mysql client alive until slave is configured.

Note : If you are using iptables firewall on server, then use the command below to open connections to mysql.

iptables -I INPUT 1 -p tcp --dport 3306 -m state --state NEW -j ACCEPT
service iptables save
service iptables restart

Open another client and check the log file name and position on master.

mysql> show master status \G
File  : mysql-bin.000001
Position :406

Make a note of these and proceed to next steps….

Prepare the slave server

Edit /etc/my.cnf and add one line in [mysqld] section
server-id=2

Now restart service on slave and configure it to connect and replicate from master server.

service mysqld restart
mysql> change master to master_host='centos1', master_user='repl', master_password='pass123', master_log_file='mysql-bin.000001', master_log_pos=406;
mysql> start slave;

Now the slave is ready.

Testing the setup

Unlock the server and add some data.

mysql> unlock tables ;
Query OK, 0 rows affected (0.00 sec)
mysql> use test
Database changed
mysql> create table a (id int(2) );
Query OK, 0 rows affected (0.02 sec)

Now go to slave and check if the data has been replicated.

mysql> use test
Database changed
mysql> show tables ;
+----------------+
| Tables_in_test |
+----------------+
| a              |
+----------------+
1 row in set (0.00 sec)

Let us talk about Windows Services in this session. All the windows operating systems are running  with a bundle of essential services, which helps to run the required tasks. When you face some trouble with some component or tasks of operating system, you always looks if the services are running fine or not. It is easy to check a local service in single system. But when it comes to a huge infrastructure management you have to find an alternative ways to check the service status. The usual way of checking the windows services status is from the services window from the control panel.

Start -> Settings -> Control Panel -> Administrative Tools -> Services

You can  start, stop, restart all windows services from the above window based on the requirement. It is very important to perform when you make some changes to OS settings to get it effected.  Most of the time, you would have seen a restart of the complete system solving the issue, the main reason of your issue might be a crashed windows service, which comes back when you reboot the system. When ever you install any application , it will add its own particular service to the OS. Most of the application based services are set to be run automatically. This mean that service will start automatically when the System boots.

We can check services running in a remote server using the same window. Remote server should be accessible from the local server. You need to right click on Services(Local) and select connect to another computer, which will give you a window to enter the remote server name or IP. In the bellow screen I have entered our Server name(Panayola121).

Press OK to connect the remote computer. It will give you the complete Service status of the remote computer. You should have local administration rights in the remote server to mange the windows services of it. See the bellow services of the remote server connected.

Backup of a Windows OS Service Status.

It is always good to have a backup of the service status running in your server.  This will help you in trouble shooting many kind of problems you face in day today administration life. In order to backup the service status of a server you simply need to export the windows service status to a file using the built in option  Export List. You can export the complete service status or only the selected Services.

Right click on Services and click on Export List.

It will also allow you to export only the selected Service Status to the backup file, for that just select the service you required to backup and do Export List and before saving the file tick on . Now It will ask you to save the file and you need choose the file format to be saved.  It is always good to have the output in excel sheet , so I would choose the csv format.

Once you export the service status, you can move  csv file to a safe (archive) location for the future requirement. You can always refer the service status to compare the current service status.

Manage the Windows Services

When you make some changes in the Windows environment it is always good to reboot the system if you really don’t know what are the dependent services running. But if you know exactly what are the Windows Services related to the changes you have made, you can restart (stop and start again) services from the Services window instead of rebooting the OS which will reduce the down time for your critical application running in the server.

To Start, Stop, Restart a service you can right click on the particular service and choose the appropriate option.

Else choose Properties or double click on the service and it will show you the service properties with few advanced options.For example, when I double click on Automatic Update Service, I get the following options, based on which tabs  I choose in the Automatic Update Properties window.

General Tab                                                                                                                Log On tab

Recovery Tab                                                                                                             Dependencies tab

We will continue this topic in another session with more details.

Hope you find this article useful. Leave a comment to discuss more

The LVM can:

• Resize Volumes online
• Create Snapshots
• Mirror Volumes

…and more.

First , we need some partitions. We make them using fdisk tool or any other tool of your choice. The only thing you need to remember is to set the partition type to 8e. That will make it LVM Ready.

Once the partitions are ready, we can make them Physical Volumes (PV) using the pvcreate command. Remember , data is stored by LVM in blocks of space called Physical Extents (PE). This can be set by pvcreate command and vary. Default is 4MB.  Number of PEs and their size plays an important role according to the type of data you are going to store in there.

When we have our Physical Volumes ready, we will then proceed to create our Volume Group (VG). Think about volume groups as a collection of PVs. You can add PVs to a VG to add more space whenever you need.

Once a Volume Group is available, we can then define Logical Volumes (LV) using the space from VG. Think about LVs as partitions in VG. LVs are available to us for formatting with any file system and mount. LVs can be resized easily according to data requirement and space availability in the containing VG.

How to create a LV in LVM

Here, I am having 2 disks /dev/sdb and /dev/sdc each 1 GB in size. I am going to create one partition in each and mark them as type 8e (LVM).  Then I would create a VG (newvg) with both the partitions (/dev/sdb1 & /dev/sdc1 ) as members. So the VG  will be 2GB and I will create a LV (logvol01) of 500 MB from the VG. We will format the LV with ext3 filesystem and mount it under /mnt/logvol01 . Terminal output is given below.

[root@server ~]# fdisk -cu /dev/sdb

Command (m for help): n
Command action
   e   extended
   p   primary partition (1-4)
p
Partition number (1-4): 1
First sector (2048-2097151, default 2048): 
Using default value 2048
Last sector, +sectors or +size{K,M,G} (2048-2097151, default 2097151): 
Using default value 2097151

Command (m for help): t
Selected partition 1
Hex code (type L to list codes): 8e
Changed system type of partition 1 to 8e (Linux LVM)

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.
[root@server ~]# fdisk -cu /dev/sdc

Command (m for help): n
Command action
   e   extended
   p   primary partition (1-4)
p
Partition number (1-4): 1
First sector (2048-2097151, default 2048): 
Using default value 2048
Last sector, +sectors or +size{K,M,G} (2048-2097151, default 2097151): 
Using default value 2097151

Command (m for help): t
Selected partition 1
Hex code (type L to list codes): 8e
Changed system type of partition 1 to 8e (Linux LVM)

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.

[root@server ~]# 
[root@server ~]# pvcreate /dev/sdb1 /dev/sdc1
  Writing physical volume data to disk "/dev/sdb1"
  Physical volume "/dev/sdb1" successfully created
  Writing physical volume data to disk "/dev/sdc1"
  Physical volume "/dev/sdc1" successfully created
[root@server ~]#
[root@server ~]# vgcreate newvg /dev/sdb1 /dev/sdc1
  Volume group "newvg" successfully created
[root@server ~]#
[root@server ~]# vgs newvg
  VG    #PV #LV #SN Attr   VSize VFree
  newvg   2   0   0 wz--n- 1.99g 1.99g
[root@server ~]#
[root@server ~]# lvcreate -n logvol01 -L 500M newvg
  Logical volume "logvol01" created
[root@server ~]#
[root@server ~]# lvdisplay newvg/logvol01
  --- Logical volume ---
  LV Name                /dev/newvg/logvol01
  VG Name                newvg
  LV UUID                XN2uEM-Nkbc-JDiT-43as-C5PG-KF2y-1Hg0hn
  LV Write Access        read/write
  LV Status              available
  # open                 0
  LV Size                500.00 MiB
  Current LE             125
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:2

[root@server ~]# mkfs.ext3 /dev/newvg/logvol01
mke2fs 1.41.12 (17-May-2010)
Filesystem label=
OS type: Linux
Block size=1024 (log=0)
Fragment size=1024 (log=0)
Stride=0 blocks, Stripe width=0 blocks
128016 inodes, 512000 blocks
25600 blocks (5.00%) reserved for the super user
First data block=1
Maximum filesystem blocks=67633152
63 block groups
8192 blocks per group, 8192 fragments per group
2032 inodes per group
Superblock backups stored on blocks:
        8193, 24577, 40961, 57345, 73729, 204801, 221185, 401409

Writing inode tables: done
Creating journal (8192 blocks): done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 36 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.
[root@server ~]# mkdir /mnt/logvol01
[root@server ~]# mount /dev/newvg/logvol01 /mnt/logvol01
[root@server ~]# mount | grep logvol01
/dev/mapper/newvg-logvol01 on /mnt/logvol01 type ext3 (rw)
[root@server ~]# df -h /mnt/logvol01
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/newvg-logvol01
                      485M   11M  449M   3% /mnt/logvol01
[root@server ~]#

If you are a GUI lover, you could do this using System->Administration->Logical Volume Management. We will look at resizing Logical Volumes, Snapshots and more in future.

Hope you have enjoyed this article. As usual, feel free to try, share and discuss.

Today we are going to look at both ways of enabling swap space on your linux box. i.e. Swap partition and Swap file. Get ready and load up our ultimate weapon, the terminal.

1. Using a Partition as SWAP

First, we will create a partition. In this case I am creating a 512 M partition in the second disk  ( /dev/sdb ) of my computer. What we need to make sure is that the partition type is set to 82 instead of the default 83. After the partition is created, we will make it ready as swap space and then enable swap on it. Here’s what my terminal output looked like.

[root@server ~]# fdisk -cu /dev/sdb

Command (m for help): n
Command action
   e   extended
   p   primary partition (1-4)
p
Partition number (1-4): 1
First sector (2048-2097151, default 2048):
Using default value 2048
Last sector, +sectors or +size{K,M,G} (2048-2097151, default 2097151): +512M

Command (m for help): t
Selected partition 1
Hex code (type L to list codes): 82
Changed system type of partition 1 to 82 (Linux swap / Solaris)

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.
[root@server ~]# mkswap /dev/sdb1
Setting up swapspace version 1, size = 524284 KiB
no label, UUID=93c1f282-a65d-4b4b-8ea5-9f9df5320309
[root@server ~]# free -m
             total       used       free     shared    buffers     cached
Mem:           499        118        380          0          6         55
-/+ buffers/cache:         56        443
Swap:            0          0          0

[root@server ~]# swapon -v /dev/sdb1
swapon on /dev/sdb1
swapon: /dev/sdb1: found swap signature: version 1, page-size 4, same byte order
swapon: /dev/sdb1: pagesize=4096, swapsize=536870912, devsize=536870912
[root@server ~]#
[root@server ~]# free -m
             total       used       free     shared    buffers     cached
Mem:           499        118        380          0          6         55
-/+ buffers/cache:         56        443
Swap:          511          0        511
[root@server ~]#
[root@server ~]#

As you can see in the free -m result, we have successfully enabled 512 M swap space in the system. If you want to make this swap available permanently in the system, add it to the /etc/fstab file as below.

/dev/sdb1 swap swap defaults 0 0


That will make it available even if you reboot the system. Now let’s take a look at how to do the same thing without making a partition, in the following section.

2. Using a file as SWAP

First, we create a file using the dd command. Then we make the swap available from the file. This method is particularly useful when you don’t have enough free space available on disk to create a new partition.

[root@server ~]# dd if=/dev/zero of=/opt/swap.file bs=512 count=1000000

1000000+0 records in
1000000+0 records out
512000000 bytes (512 MB) copied, 18.8782 s, 27.1 MB/s
[root@server ~]#
[root@server ~]# mkswap /opt/swap.file
mkswap: /opt/swap.file: warning: don't erase bootbits sectors
        on whole disk. Use -f to force.
Setting up swapspace version 1, size = 499996 KiB
no label, UUID=880adc48-0735-41a1-a3c1-63a59d852513
[root@server ~]#
[root@server ~]# free -m
             total       used       free     shared    buffers     cached
Mem:           499        476         22          0          3        410
-/+ buffers/cache:         62        436
Swap:            0          0          0
[root@server ~]# chmod 0600 /opt/swap.file
[root@server ~]# swapon -v /opt/swap.file
swapon on /opt/swap.file
swapon: /opt/swap.file: found swap signature: version 1, page-size 4, same byte           order
swapon: /opt/swap.file: pagesize=4096, swapsize=512000000, devsize=512000000
[root@server ~]# free -m
             total       used       free     shared    buffers     cached
Mem:           499        476         22          0          3        410
-/+ buffers/cache:         63        436
Swap:          488          0        488
[root@server ~]#

For /etc/fstab , please use the below line :

/opt/swap.file swap swap defaults 0 0

Hope you find this article useful. Feel free to try, share and discuss.

We have already discussed the RAID 0 and Delete RAID Logical Drive in our previous articles.  Let’s see what is RAID1+0 and how can we configure RAID1+0 in a HP Server. RAID 1+0 is mixture of RAID 0 (Stripping) and RAID 1 (Mirroring). It also delivers the benefits of both in a single system. As you can see in the picture, it stripes the mirrored drives.  Thus, it will have the security of mirroring all data on another set of drives while striping of each set of drives to increases the data transfer speed. RAID 1+0 is the perfect solution for the servers running databases and high availability applications which demands data read/write efficiency and high fault tolerance. RAID 1+0 requires minimum four drives.

Power on the server and wait for the Array Controller ROM utility to prompt you to press F8 to run RAID configuration.

Press F8 to enter the utility then you will get the Array controller utility to create logical drives. Select Create logical drive and press Enter

Press Enter to create the logical drive.

Press F8 to Save the configuration. This will create the RAID 0 Logical Drive.

Press Enter to continue. That will take you to the main menu again. It is good to verify the Logical drive we created. For that select View Logical Drive and press Enter

That will show you the logical drive you have just created. Since I have selected all eight Physical disks (146GB each disk) available, for this logical drive we have got 546 TB capacity. Since it will mirror you will get only the half size of the total capacity of the drives. You can select the Logical Drive and press  Enter to see the physical disk array(total number of disk used in this RAID 1+0 local drive.When you quit from the utility server will continue the boot process.

See also how to delete the  Logical Drives

Hope you find this article useful. Leave a comment to discuss more.

Sometimes  you  need to remove existing RAID configuration and create another RAID Logical Drive based on the requirement. When you need to have more space in your server or when you wanted to have more performance for your application, you will  need to choose the right RAID configuration. That we will discuss later. Here is the quick way of deleting a RAID Logical drive  in a HP server. But removing the RAID configuration will effect your data. We recommend you to backup your data before trying this.

Power on the Server and wait for the Array Controller utility to prompt you to press F8 to enter the RAID configuration utility.It will show you the  main menu of RAID configuration utility.From main menu Choose (using the down arrow key) Delete Logical Drive and Press Enter.You can now view the existing Logical drive , which you need to Delete. Press F8 to delete the logical drive.

Press F3 to delete the logical drive.  This will be the last confirmation before you delete (loose the data from the existing drive) the Logical drive. When you press F3, it will delete and Save all the configuration change.

When you press Enter  it will take you to the main menu. To verify the removal of existing Logical drive , Choose View the Logical Drive and press  Enter.

Press Enter  and it should show you  the bellow screen if the Logical Drive removal you performed was successful.

From main menu, you can start creating the new RAID Logical drive based on your requirement.

Hope you find this article useful. Leave a comment to discuss more.

RAID is the short form of Redundant Array of Independent Disks which is a way of storing the same data in different places on multiple hard disks.  There are different  RAID level in the industry now. In that most popular are  four levels.

• RAID 0
• RAID 1
• RAID 5
• RAID 1+0

We are going to discuss about the basic RAID level in this article. In RAID level 0(zero) disks are striped so no redundancy of data. This level deliver the best performance without fault-tolerance. I have taken one HP Server to show you how  we can configure RAID level 0. We need to have minimum two disk to configure RAID 0. When one of disk fails, you will lose data as we have striped the drives. So it is very important that when you use RAID 0 , you need to take regular backup of your data. Also this level is not recommended for critical production servers.

Lets start configure RAID in a HP Server. Power on the Server and wait for the Array Controller ROM utility to prompt you to press F8 to run Option ROM configurations for Arrays. Press F8 to enter the utility then you will get the Array controller utility to create logical drives.  Select Create logical drive and press Enter.Here we can see  the Available Physical Drives. Choose the drives you want to add to RAID 0 logical drive. Remember RAID-0 required minimum two disks. so select at least two drives. Once you selected drives use tab button to navigate  to the next option RAID Configuration and choose RAID 0.Press Enter to create the logical drive.

Press F8 to Save the configuration. This will create the RAID 0 Logical Drive.

Press Enter to continue. That will take you to the main menu again. It is good to verify the Logical drive we created. For that select View Logical Drive and press Enter

That will show you the logical drive you have just created. Since I have selected all eight Physical disks (146GB each disk) available, for this logical drive we have got 1 TB capacity.

You can Select the Logical Drive and press  Enter to see the physical disk array(total number of disk used in this RAID-0 local drive.

 You need to press ESC to return to main menu. when you done press ESC again to quit from the utility and server will continue the boot process.

See also how to delete the  Logical Drives

Hope you find this article useful. Leave a comment to discuss more.

HP Warranty check.

Option-1

You can create the list of products you want to check, need to enter the serial number and other information requested and click on Add.

When you have finished adding the serial numbers you want to check, click the Display Warranty Information button

Click Here

Option-2

This link have two choices, you can check the product warranty manually or automatically by clicking on the START DETECTION button.

For Manual warranty check

Select the country where you would like have the product serviced or the country you purchased your product, and enter the serial number and product number and click on Submit button.

Click Here

Dell Warranty Check

Here is the link. 

If you are browsing this web link from your Dell system, then it automatically find your Service Tag and display the warranty information.

Otherwise you need to enter the Service Tag of the product and click on Continue button, which will show you the product warranty information.

IBM Warranty Check

Single Production Warranty check

The fields indicated with an asterisk are required to complete this transaction; other fields are optional. If you do not want to provide us with the required information, please use the “Back” button on your browser to return to the previous page, or close the window or browser session that is displaying this page

Warranty Link

Multiple warranty lookup

The multiple warranty tool allows you to get the warranty status of multiple systems at one time and provide them in a convenient HTML page.

Warranty Link

Hope the above information is useful for  you. Leave a comment if  you want to discuss more.

PHP and MySQL are two unique open source projects. While PHP is an excellent programming language, MySQL is the Database choice of millions of softwares, websites and companies out there.

In this series, we will look at how to use PHP to connect and manipulate data stored inside MySQL. In the first part, I am going to demonstrate how to connect to a MySQL database and read data from a table and display the results.

For this we need to first install Apache, MySQL and PHP. We will also create a database and a table in MySQL. If you haven’t done this earlier, follow the below shell commands.

sudo apt-get update
sudo apt-get install apache2 php5 php5-mysql php5-cgi mysql-server
mysqladmin -u root -p create testdb

Remember to set a password for root user when asked. Also use the same password for the mysqladmin command. Now it is time for us to login to MySQL as root and create a table. We will also create a user in MySQL with less privileges to use that database and table. It is not wise to use root access in your applications as it would lead to lot of destruction if someone was able to crack/hack your application. We will also populate one sample entry in our table for PHP to read.

Here is what I did on my terminal.

mysql -u root -p
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 47
Server version: 5.1.58-1ubuntu1 (Ubuntu)

mysql> use testdb;
Database changed
mysql> create table example (
    -> id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
    -> name VARCHAR(50),
    -> mobile VARCHAR(20)
    -> );
Query OK, 0 rows affected (0.05 sec)

mysql> create user phpuser@localhost identified by 'bigpassword';
Query OK, 0 rows affected (0.00 sec)

mysql> grant select,insert,delete,update on testdb.example to phpuser@localhost;
Query OK, 0 rows affected (0.00 sec)

mysql> flush privileges ;
Query OK, 0 rows affected (0.00 sec)

mysql> insert into example (name,mobile) values ('John','+919900502392');
Query OK, 1 row affected (0.00 sec)

mysql> \q

Ok. Now we are all set to start with our PHP code. Make sure that Apache is running by browsing to http://localhost in your computer. You should be seeing a “It Works !” page. We will also create a test.php file in the root directory of  our web server and assign rights to our user so that we can edit it.

sudo apt-get update
sudo touch /var/www/test.php
sudo chown panayola:panayola /var/www/test.php

Open this file ( /var/www/test.php ) your favorite text editor and paste the following code.

<?php
//First, connect to the DB. Note that we are using the same user name and password we created
//Do not use root username and password here as it is unsafe.

$dblink=mysql_connect('localhost','phpuser','bigpassword') or die('Could not connect to Database Server');

//ok. That means we are connected. Let's select the database.
mysql_select_db('testdb') or die('Could not select DB');

//Now we can prepare a SQL query and send it to the Server
//We are using the $dblink we created using the mysql_connect() function call earlier to send the query.
$query="SELECT * from example";
$result=mysql_query($query,$dblink) or die('MySQL query Failed' . mysql_error());

//We have the result ! Let's fetch the data and display it.
//Note that the data comes as an array, so we need to split it into variables.
$row=mysql_fetch_row($result);

$id=$row['0'];
$name=$row['1'];
$mobile=$row['2'];

echo "<h1> MySQL data : ID $id , NAME $name , MOBILE $mobile  </h1>";

//Close the connection
mysql_close($dblink);
?>

Now open your browser and open the url http://localhost/test.php . You should be able to see the page below !.

This was only about reading just one row of data from the example table. In the next part, we will look at how to read multiple rows and display the results as a HTML table.

Hope you enjoyed this article. Feel free to try, share and discuss.