Posts Tagged ‘UNIX’

Last Command Examples For Linux And Unix

May 8th, 2022, posted in Solaris

How to find out last logins of users and times informations on Linux/Unix-like operating systems ?

You need to use the last command to show who has recently used the server and logged in and out date/time.


The last command reads listing of last logged in users from the system file called /var/log/wtmp or the file designated by the -f options.


To find out when a particular user last logged in to the Linux or Unix server.


The basic syntax is:

last [userNameHere] last [tty] last [options] [userNameHere]

If no options provided last command displays a list of all users logged in (and out) since /var/log/wtmp file was created. You can filter out results by supplying names of users and tty’s to show only those entries matching the username/tty.

last command examples

To find out who has recently logged in and out on your server, type:
$ last
Sample outputs:

root     pts/1       Tue Jan 28 05:59   still logged in   
root     pts/0       Tue Jan 28 04:08   still logged in   
root     pts/0       Sat Jan 25 06:33 - 08:55  (02:22)    
root     pts/1       Thu Jan 23 14:47 - 14:51  (00:03)    
root     pts/0       Thu Jan 23 13:02 - 14:51  (01:48)    
root     pts/0       Tue Jan  7 12:02 - 12:38  (00:35)    
wtmp begins Tue Jan  7 12:02:54 2014

You can specifies a file to search other than /var/log/wtmp using -f option. For example, search /nas/server/webserver/.log/wtmp:
$ last -f /nas/server/webserver/.log/wtmp
last -f /nas/server/webserver/.log/wtmp userNameHere

List all users last logged in/out time

last command searches back through the file /var/log/wtmp file and the output may go back to several months. Just use the less command or more command as follows to display output one screen at a time:
$ last | more
last | less

List a particular user last logged in

To find out when user vivek last logged in, type:
$ last vivek
$ last vivek | less
$ last vivek | grep 'Thu Jan 23'

Sample outputs:

Fig. 01 Displaying out when user vivek last logged in on server

Fig. 01 Displaying out when user vivek last logged in on server


Tar: .file too large to archive. Use E function modifier

April 30th, 2018, posted in Solaris

Tar, .file too large to archive, Use E function modifier,E function modifier,solaris 10,unix,linux,sun solaris 10,solaris administrator,Using TAR for big files

tar: .file too large to archive. Use E function modifier.

Using TAR for big files ( > 8GB)

In Unix environment, If you are trying to “tar” OS files that is bigger than 8 GB of size. Following error is observed.

Regular tar command:

tar -cvf test.dmp.tar test.dmp


tar: test.dmp too large to archive.  Use E function modifier.


tar -cvEf test.dmp.tar test.dmp

Unix for DBA

May 24th, 2017, posted in Solaris

Below are some of the basic unix commands which will be useful for Oracle DBA.

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


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 ‘<ID>’

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/ > /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/ > /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/ > /dev/null 2>&1