As DBA you need to use frequent OS command, here I would like to share you some of the important day to day commands:
1. To delete files older than N number of days ? (Useful in delete log, trace, tmp file )
find . -name ‘*.*’ -mtime +[N in days] -exec rm {} \;
Example : find . -mtime +5 -exec rm {} \;
(This command will delete files older then N days in that directory
2. To list files modified in last N days
find . -mtime - -exec ls -lt {} \;
Example: find . -mtime +3 -exec ls -lt {} \;1
So to find files modified in last 3 days
3. To sort files based on Size of file ?
ls -l | sort -nk 5 | more
useful to find large files in log directory to delete in case disk is full
4. To find files changed in last N days
find -mtime -N –print
Example: find -mtime -2 -print
5. To extract cpio file
cpio -idmv < file_name (Don’t forget to use sign < before file name)
6. To find CPU & Memory detail of linux
cat /proc/cpuinfo (CPU)
cat /proc/meminfo (Memory)
7. To find if Operating system in 32 bit or 64 bit ?
For solaris use command
isainfo -v
If you see out put like
32-bit sparc applications
That means your O.S. is only 32 bit
but if you see output like
64-bit sparcv9 applications
32-bit sparc applicationsabove means your o.s. is 64 bit & can support both 32 & 64 bit applications
8. To find if any service is listening on particular port or not ?
netstat -an | grep {port no}
Example: netstat -an | grep 1523
9. To find Process ID (PID) associated with any port ?
This command is useful if any service is running on a particular port (389, 1521..) and that is run away process which you wish to terminate using kill command
lsof | grep {port no.} (lsof should be installed and in path)
9. To change a particular pattern in a file ?
Open file using vi or any other editor, go in escape mode (by pressing escape) and use
:1,$s/old_pattern/new_parameter/gc ( g will change globally, c will ask for confirmation before changing )
10. To find a pattern in some file in a directory ?
grep pattern file_name ( to find pattern in particular file )
grep pattern * ( in all files in that directory )
If you know how to find a pattern in files in that directory recursively please answer that as comment
11. To create symbolic link to a file ?
ln -s pointing_to symbolic_name
Example : ln -s b a
If you want to create symbolic link from a -> b
(Condition:you should have file b in that directory & there should not be any file with name a)
12. To setup cronjob (cronjob is used to schedule job in Unix at O.s. Level )
crontab -l( list current jobs in cron)
crontab -e ( edit current jobs in cron)
_1_ _2_ _3_ _4_ _5_ executable_or_job
Where
1 – Minutes (0-59)
2 – Hours ( 0-24)
3 – day of month ( 1- 31 )
4 – Month ( 1-12)
5 – A day of week ( 0- 6 ) 0 -> sunday 1-> monday
e.g. 0 3 * * 6 Means run job at 3AM every saturday
This is useful for scheduling tablespace threshold, ftp, rman backup or removed old log files, or other scripts regularly.
Sample Scheduled backup:
$ crontab –l
Rman Database:
|
00
|
20
|
*
|
*
|
1,4
|
/u07/rman/scripts/call_dbbkup_cm0.scp
|
00
|
15
|
*
|
*
|
6
|
/u07/rman/scripts/offbkup_rman.sh
|
00
|
20
|
*
|
*
|
0,2,3,6
|
/u07/rman/scripts/call_arch_bkup.scp
|
OTA Database:
|
50
|
23
|
*
|
*
|
0,2,3,6
|
/u01/ota/dailyexp_ota.sh
|
50
|
23
|
*
|
*
|
1,4
|
/u01/ota/offbkup_ota.sh
|
15
|
14
|
*
|
*
|
0,1,2,3,4,6
|
/u01/ota/morning_arch.sh
|
How to kill all similar processes with single command (in this case opmn)
ps -ef | grep opmn |grep -v grep | awk ‘{print $2}’ |xargs -i kill -9 {}
Locating Files under a particular directory
find . -print |grep -i test.sql
Using AWK in UNIX
To remove a specific column of output from a UNIX command – for example to determine the UNIX process Ids for all Oracle processes on server (second column)
ps -ef |grep -i oracle |awk '{ print $2 }'
Changing the standard prompt for Oracle Users
Edit the .profile for the oracle user
PS1="`hostname`*$ORACLE_SID:$PWD>"
Display top 10 CPU consumers using the ps command
/usr/ucb/ps auxgw | head -11
Show number of active Oracle dedicated connection users for a particular ORACLE_SID
ps -ef | grep $ORACLE_SID|grep -v grep|grep -v ora_|wc -l
Display the number of CPU’s in Solaris
psrinfo -v | grep "Status of processor"|wc -l
Display the number of CPU’s in AIX
lsdev -C | grep Process|wc -l
Display RAM Memory size on Solaris
prtconf |grep -i mem
Display RAM memory size on AIX
First determine name of memory device
lsdev -C |grep mem
then assuming the name of the memory device is ‘mem0’
lsattr -El mem0
Swap space allocation and usage
Solaris : swap -s or swap -l
Aix : lsps -a
Total number of semaphores held by all instances on server
ipcs -as | awk '{sum += $9} END {print sum}'
View allocated RAM memory segments
ipcs -pmb
Manually deallocate shared memeory segments
ipcrm -m ''
Show mount points for a disk in AIX
lspv -l hdisk13
Display amount of occupied space (in KB) for a file or collection of files in a directory or sub-directory
du -ks * | sort -n| tail
Display total file space in a directory
du -ks .
Cleanup any unwanted trace files more than seven days old
find . *.trc -mtime +7 -exec rm {} \;
Locate Oracle files that contain certain strings
find . -print | xargs grep rollback
Locate recently created UNIX files (in the past one day)
find . -mtime -1 -print
Finding large files on the server (more than 100MB in size)
find . -size +102400 -print
Crontab :
To submit a task every Tuesday (day 2) at 2:45PM
45 14 2 * * /opt/oracle/scripts/tr_listener.sh > /dev/null 2>&1
To submit a task to run every 15 minutes on weekdays (days 1-5)
15,30,45 * 1-5 * * /opt/oracle/scripts/tr_listener.sh > /dev/null 2>&1
To submit a task to run every hour at 15 minutes past the hour on weekends (days 6 and 0)
15 * 0,6 * * opt/oracle/scripts/tr_listener.sh > /dev/null 2>&1
