Tag: linux command

Flush Linux Buffer Cache

Posted on by Osama Mustafa in Operating system
Cache is used to keep data to use frequently by operating system,  But sometimes memory is getting low linux provide some memory Command line to monitor Memory status Check the below link :-

1- Linux Check Memory Usage Here.
2- 18 Command Line Tools to Monitor Linux Performance here.

There are options available to flush cache of linux memeory :-

Flush everything ( Pagecache, dentries and inodes )  :-

 sync; echo 3 > /proc/sys/vm/drop_caches.

Flash dentries and inodes :-

 sync; echo 2 > /proc/sys/vm/drop_caches

Flash PageCache only

sync; echo 1 > /proc/sys/vm/drop_caches

All the command should be Run As root.

Schudle the above command as job using crontab , choose from the above command what you need :-

0  *  *  *  *  /root/memory.sh

Memorysh –> should be contain one the above script run as root.

Thank you
Osama mustafa

 

Useful Linux Commands For DBA

Posted on by Osama Mustafa in Operating system 
Show Routing Table :
 
netstat -r

Check ORA errors in the Logs:

grep ^ORA- *log |cut -f2 -d"-"|cut -f1 -d:|awk '{print "ORA-" $1}'|sort -u
Inzip CPIO Files :
 
cpio -idmv <

 Sort Files By Size :

ls -l |sort -k 5

Find Command archive and move to another Folder :

find ./ -name "*.arch" -mtime +1 -exec mv {} /u01/;

Find Command archive and Remove it:

find ./ -name "*.ARC" -mtime +1 -exec rm {} \;

Find Command with Zip :

find ./ -name "*.ARC" -mtime +1 -exec gzip {} \;

 Find Command With List :





 find ./ -name “*.ARC” -mtime +1 -ls  


Thank you
Osama Mustafa



	

	

	




	
	

		
Check memory On Linux
				

					Posted on  by Osama Mustafa in Operating system				


				

	

		
Sometime you as DBA you need to check your memory On Operating System Level, i will give you some command will useful to you :


1-free -m / free -g


m : megabytes
g : gigabytes




              total    used     free   shared  buffers   cached 
 Mem:           503     451       52        0       14      293 
 -/+ buffers/cache:     143      360 
 Swap:         1027       0     1027




 another example :


free -t -m






       total       used       free     shared    buffers     cached
Mem:           750        625        125          0         35        335
-/+ buffers/cache:        253        496
Swap:          956          0        956
Total:        1707        625       1082




2-vmstat




procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us sy id wa
1  0      0 131620  35432 341496    0    0    42    82  737  1364 15  3 81  1


 


 


 


 


3-top 


 




 


 




4-gnome-system-monitor


 




 


 


The below Command for clear cache memory in linux 






sync; 


echo 3 > /proc/sys/vm/drop_caches




 you can make it as job in linux save in it crontab 






0 * * * * /root/clearcache.sh


 




Create a file in '/root' called 'clearcache.sh' with the following content:






#!/bin/sh  
 sync; echo 3 > /proc/sys/vm/drop_caches




 


  


Thank you 


osama mustafa 



	

	

	




	
	

		
Backup an entire hard disk using dd command
				

					Posted on  by Osama Mustafa in Operating system				


				

	

		


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