Linux Remove or Clear the Last Login Information

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https://www.cyberciti.biz/faq/howto-display-clear-last-login-information/

The /var/log/lastlog file stores user last login information. This is binary file and act as database times of previous user logins. You need to use lastlog command to formats and prints the contents of the last login log /var/log/lastlog file.

lastlog command

The lastlog command shows the most recent login of all users or of a given user. The Following information is printed using lastlog command:

=> The login-name

=> Port

=> Last login time

Task: Display last login information

Simply type the lastlog command :
$ lastlog
Sample outputs:

Username         Port     From             Latest
root             tty1                      Thu Jan 25 15:23:50 +0530 2007
daemon                                     **Never logged in**
bin                                        **Never logged in**
sys                                        **Never logged in**
sync                                       **Never logged in**
vivek            tty1                      Sat Jan 27 22:10:36 +0530 2007
pdnsd                                      **Never logged in**
sshd                                       **Never logged in**
messagebus                                 **Never logged in**
bind                                       **Never logged in**
sweta           tty1                      Sat Jan 27 19:55:22 +0530 2007

Note: If the user has never logged in the message “**Never logged in**” will be displayed instead of the port and time.

Task: Clear last login information by deleting /var/log/lastlog

Simply overwrite /var/log/lastlog file. You must be the root user. First make a backup of /var/log/lastlog:
# cp /var/log/lastlog /root
Now overwrite file using any one of the following command:
# >/var/log/lastlog
OR
# cat > /var/log/lastlog

Press CTR+D to save the changes.

last and lastb commands

Use last or lastb command to display listing of last logged in users:
$ last
OR
$ lastb
Sample outputs:

root     pts/1        10.1.6.120       Tue Jan  7 16:43   still logged in   
root     pts/0        10.1.6.120       Tue Jan  7 15:52   still logged in   
root     pts/0        10.1.6.120       Tue Jan  7 11:20 - 15:07  (03:47)    
root     pts/1        10.1.6.120       Tue Jan  7 07:07 - 09:50  (02:43)    
root     pts/0        10.1.6.120       Tue Jan  7 05:00 - 07:22  (02:21)    
root     pts/0        10.1.6.120       Mon Jan  6 14:16 - 16:36  (02:20)    
root     pts/0        10.1.6.120       Sun Jan  5 16:37 - 17:01  (00:23)    
root     pts/0        10.1.6.120       Sun Jan  5 15:12 - 15:39  (00:26)    
root     pts/0        10.1.6.120       Sun Jan  5 14:45 - 15:05  (00:20)    
root     pts/2        10.1.6.120       Sun Jan  5 12:53 - 15:46  (02:53)    
root     pts/0        10.1.6.120       Sun Jan  5 12:52 - 12:53  (00:00)    
root     pts/1        10.1.6.120       Sun Jan  5 11:09 - 14:29  (03:20)    
root     pts/0        10.1.6.120       Sun Jan  5 10:05 - 12:19  (02:14)    
reboot   system boot  2.6.32-431.3.1.e Sun Jan  5 10:02 - 16:48 (2+06:46)   
root     pts/0        10.1.6.120       Sun Jan  5 09:58 - down   (00:00)    
root     pts/0        10.1.6.120       Sun Jan  5 03:33 - 05:45  (02:12)    
root     pts/1        10.1.6.120       Sat Jan  4 15:06 - 17:28  (02:21)    
root     pts/0        10.1.6.120       Sat Jan  4 13:46 - 15:58  (02:11)    
root     pts/0        10.1.6.120       Sat Jan  4 05:05 - 07:16  (02:11)    
root     pts/1        10.1.6.120       Fri Jan  3 14:29 - 15:44  (01:15)    
root     pts/0        10.1.6.120       Fri Jan  3 13:20 - 15:32  (02:11)    
root     pts/0        10.1.6.120       Thu Jan  2 05:19 - 05:32  (00:13)    
root     pts/0        10.1.6.120       Tue Dec 31 13:57 - 16:06  (02:09)    

wtmp begins Tue Dec 31 13:57:23 2013

last and lastb use /var/log/wtmp and /var/log/btmp files to log information. You can use the following command to clear wtmp/btmp:
# >/var/log/wtmp
# >/var/log/btmp

For more information see man pages – lastlog(8), last(1), login(1), wtmp(5)