Backup an entire hard disk using dd command

The ‘ dd ‘ command is one of the original Unix utilities and should be in everyone’s tool box. It can strip headers, extract parts of binary files and write into the middle of floppy disks; it is used by the Linux kernel Makefiles to make boot images. It can be used to copy and convert magnetic tape formats, convert between ASCII and EBCDIC, swap bytes, and force to upper and lowercase. 

# dd –help

full hard disk copy

dd if=/dev/hdx of=/dev/hdy
dd if=/dev/hdx of=/path/to/image
dd if=/dev/hdx | gzip > /path/to/image.gz

Hdx could be hda, hdb etc. In the second example gzip is used to compress the image if it is really just a backup.  

Restore Backup of hard disk copy

dd if=/path/to/image of=/dev/hdx

gzip -dc /path/to/image.gz | dd of=/dev/hdx  

MBR backup

In order to backup only the first few bytes containing the MBR and the partition table you can use dd as well.

dd if=/dev/hdx of=/path/to/image count=1 bs=512 

MBR restore

dd if=/path/to/image of=/dev/hdx

Add “count=1 bs=446” to exclude the partition table from being written to disk. You can manually restore the table.

 “All This Information was taken from the other site , just for information to take hard-disk backup , it will be useful to use it with Oracle ”

thank you 
Osama mustafa  

Change Enterprise manager password for 11g

For the DB Control Release 11.2 and higher, you need to set the environment variable ORACLE_UNQNAME to the value of the DB_UNIQUE_NAME database parameter.

Steps :

1.Stop the DB Control
On Unix
$ emctl stop dbconsole

On Windows
Open a Command Window and type
**> emctl stop dbconsole

2.Check that the DB Control is stopped
 On Unix
$ emctl status dbconsole

On Windows
Open a Command Window and type
 **>emctl status dbconsole

3.Connect to the database as a user with DBA privilege with SQL*Plus and execute:

SQL> alter user sysman identified by ;
4.Check the new password
SQL> connect sysman/[@database_alias]
5.From the database directory $ORACLE_HOME/bin, execute:
On Unix

$ emctl setpasswd dbconsole
Provide the new SYSMAN password
On Windows

**>: emctl setpasswd dbconsoleProvide the new SYSMAN password
6.Restart the DB Control
On Unix
$ emctl start dbconsole
On Windows
Open a DOS Command Window and type
**>: emctl start dbconsole

Thank you 

Osama Mustafa