Useful Linux command - last

[root@s1 ~]# man last
Last searches back through the file /var/log/wtmp (or the 
file designated by the -f flag) and displays a list of all 
users logged in (and out) since that file was created.

[root@s1 ~]# last -R
root     pts/0        Fri Oct 14 00:17   still logged in
root     pts/0        Thu Oct 13 15:31 - 15:32  (00:00)
root     pts/0        Thu Oct 13 14:15 - 14:17  (00:02)
root     pts/0        Thu Oct 13 11:59 - 13:42  (01:43)
root     pts/1        Tue Oct 11 08:24 - 08:24  (00:00)
root     pts/0        Tue Oct 11 08:17 - 18:44  (10:27)
root     pts/0        Tue Oct 11 02:41 - 04:40  (01:58)
reboot   system boot  Tue Oct 11 02:37         (2+21:49)
root     pts/0        Tue Oct 11 02:22 - down   (00:13)
reboot   system boot  Tue Oct 11 02:22          (00:14)
root     pts/1        Tue Oct 11 02:17 - 02:18  (00:00)
root     pts/1        Tue Oct 11 02:16 - 02:16  (00:00)
root     pts/0        Tue Oct 11 01:10 - down   (01:10)
reboot   system boot  Tue Oct 11 01:03          (01:18)
root     pts/0        Tue Oct 11 00:16 - down   (00:45)
reboot   system boot  Tue Oct 11 00:12          (00:49)
root     pts/0        Mon Oct 10 21:42 - down   (02:28)
reboot   system boot  Mon Oct 10 21:37          (02:33)
root     pts/0        Mon Oct 10 21:00 - down   (00:36)
reboot   system boot  Mon Oct 10 20:55          (00:41)
root     pts/1        Mon Oct 10 20:26 - down   (00:28)
root     pts/0        Mon Oct 10 20:22 - down   (00:32)
reboot   system boot  Mon Oct 10 20:21          (00:32)
root     pts/0        Mon Oct 10 20:17 - down   (00:03)
reboot   system boot  Mon Oct 10 20:14          (00:06)
root     pts/1        Mon Oct 10 18:18 - down   (01:55)
root     pts/1        Sat Oct  8 14:59 - 18:01  (03:02)
root     pts/1        Sat Oct  8 01:50 - 01:54  (00:04)
root     pts/1        Fri Oct  7 19:48 - 20:24  (00:35)

wtmp begins Fri Oct  7 19:48:49 2005