Monday 26 August 2013

LINUX COMMANDS FOR DBA's

1) Less :
Helps in viewing the content of files page by page.
ex)
# less country12_100812.sql

2) More :
It is also equivalent to less. It shows the percent of the file viewed so far.
ex)
# more country12_100812.sql

3) cat :
It shows the contents of the file as a whole. But not page by page. Useful for small files.
ex)
# cat anaconda-ks.cfg

4) ls :
List the files present in the current directory or the path.
ex)
# ls
alldatabase_030812.sql alldb100812.sql alldb.sql Country090812.sql
country12_100812.sql lost+found mysql_030812 Prabhu.sql world.sql

5) pwd :
It shows the path of your working directory .
ex) # pwd
/home/karthik/Desktop

6) df
Displays the partitions present and the server . It also provide its disk usage and Size Used Avail Use% Mounted on
3.9G 2.0G 1.9G 52% /
495M 420K 494M 1% /dev/shm
194M 55M 130M 30% /boot
6.2G 1.5G 4.5G 25% /data
2.0G 202M 1.7G 11% /logs
485M 11M 449M 3% /tmp
3.9G 3.3G 411M 90% /usr
2.0G 976M 893M 53% /var

7) du
Retrieve the disk usage of a folder or a file.
ex)
# du -sh
963M

8) ifconfig :
Displays the IP address assigned to the server and also its other network requistics.
ex) # ifconfig
eth1
Link encap:Ethernet HWaddr 00:1D:7D:80:C1:37
inet addr:10.10.25.98 Bcast:10.10.25.255 Mask:255.255.255.0
inet6 addr: fe80::21d:7dff:fe80:c137/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:906 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 b) TX bytes:47394 (46.2 KiB)
Interrupt:21 Base address:0xa000

9) Traceroute & tracepath :
They help in finding the network delay in reaching a server from remote host.
ex)
#tracepath google.com
#tracepath 10.10.25.98

10) Ping :
Examines whether the server is reachable or not . Helps in trouble shooting the packet
losses.
ex) ping 127.0.0.1

11) netstat :
Displays the active internet connections of the servers and the port opened for the
process.

12) crontab :
Scheduler for scheduling the automated jobs like backup and other maintenance scripts.

13) Free :
Displays the total ram present in the system and their utility.
# free -m

14) Top :
It is similar to the Task manager in Windows . It displays all the process running
and their resource usage.

15) uptime :
Displays the total time after the server is booted, It also shows the load average.
ex)
# uptime
00:56:09 up 57 min, 2 users, load average: 0.00, 0.05, 0.03

16) ps :
It makes list of the current processes running on the system.

17) chmod :
Changes the permission of the files . Read , write and execute.

18) chown :
Changes the ownership of the file to some other user. We must have root permission to
change the ownership of files.

19) mkdir and rmdir:
Mkdir : Creates a directory (folder )
Rmdir : removes the directory (folder )

20) cd :
Change the active directory to required directory.

21) head :
Displays only the first 10 lines of the file as a default.

22) tail :
Displays the last 10 lines of the files as a default.

23) mv :
Move the contents from one directory to other. It is also helpful in renaming the files.

24) wc :
Displays the number of lines, word and character present in a file.

25)grep :
Search a word or a phrase in a file
ex)
#grep -i “mysql” grep_test.txt

26) find :
Search for a file with a pattern . It returns the file name.

27) locate:
Search for a file with a pattern. It returns file with a full path.

28) echo :
Prints the content given inside the quotes.
ex)
# echo "mysql is a database"
mysql is a database

29) gzip :
Compress the files with .gz as extension . Can be extracted using gunzip command.
Ex )
compress
# gzip alldb100812.sql
extract
# gunzip alldb100812.sql.gz

30 ) tar
Tape Archive file. It is a compression format used mostly in binary installation files.
It has extension of .tar

31) kill :
To terminate a running process by the pid (process id)
Ex) Kill 528412

32) who :
List the user logged into the server and their duration

33) whoami :
Displays the user name of current session.

34) sort :
Arranges the content of the files in the ascending or descending order.

35) Vi :
The editor command used to make changes in existing file . It is used widely in
scripting too as “Vim”

36) man :
Shows the manual page of a command . It gives the complete info about the
command.

37) useradd :
To add a linux user for any new process like mysql. Requires root access

38) groupadd:
To add a group in the linux. Requires root access.

39) passwd :
To change or assign password foe a user.

40 ) uname ;
It displays the system information like the OS ,kernel and processor.
# uname -a
Linux remotemysqldba.com 2.6.32-279.2.1.el6.x86_64 #1 SMP Fri Jul 20 01:55:29 UTC
2012 x86_64 x86_64 x86_64 GNU/Linux

41) scp :
Copy the files to a remote server.
ex)
scp mysql.sql root@10.101.150.21:

42) ssh:
It is to connect the remote shell .
ex)
ssh root@10.101.150.21

43 ) telnet :
It is also used to connect the remote host. But it used for checking port opening.
ex)
telnet 10.101.150.21 22


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