lastlog command prints the last login times for system accounts. Login information is read from the file /var/log/lastlog.
To print the last login of all the users:
# lastlog
To print the records of specified days older:
# lastlog -b 10 # lastlog --before 10
To print the logs more recent that specified days:
# lastlog -t 20 # lastlog --time 20
To print the last login records of specified login:
# lastlog -u mike # lastlog --user mike
Why is the /var/log/lastlog file so large?
The lastlog file is reporting to be ~1.2TB in size. This file is large since it contains information regarding the last login for all users. The UID of nfsnobody on 64 bit systems is 4294967294 or 2^32-2, with 256kB per UID.
This file is what we call a sparse file. A sparse file is a file that contains unallocated blocks or “empty space”, as it implies, it does not actually take up filesystem space.
[root@LIN-HREL8 ~]# du -sh /var/log/lastlog 40K /var/log/lastlog [root@LIN-HREL8 ~]# ls -lh /var/log/lastlog -rw-rw-r--. 1 root utmp 327G Nov 21 14:06 /var/log/lastlog [root@LIN-HREL8 ~]# df -h /var Filesystem Size Used Avail Use% Mounted on /dev/mapper/rhel-var 5.0G 2.4G 2.7G 47% /var
This file can potential give problems during backup, so ignore it.