可采用命令：w,who,last,users,finger(需yum安装)
法一：
[root@test1 ~]# who
root tty1 2015-08-19 23:15
lxh pts/0 2015-08-20 00:10 (192.168.150.1)
法二：
[root@test1 ~]# w
00:11:36 up 56 min, 2 users, load average: 0.00, 0.02, 0.00
USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT
root tty1 - 23:15 56:01 0.01s 0.01s -bash
lxh pts/0 192.168.150.1 00:10 0.00s 0.02s 0.02s sshd: lxh [priv]
法三：
[root@test1 ~]# finger
Login Name Tty Idle Login Time Office Office Phone
lxh pts/0 Aug 20 00:10 (192.168.150.1)
root root tty1 56 Aug 19 23:15
法四：
[root@test1 ~]# users
lxh root
法五：
[root@test1 ~]# last | head -n 5
lxh pts/0 192.168.150.1 Thu Aug 20 00:10 still logged in
lxh pts/1 192.168.150.1 Wed Aug 19 23:36 - 00:10 (00:34)
lxh pts/0 192.168.150.1 Wed Aug 19 23:16 - 00:10 (00:54)
root tty1 Wed Aug 19 23:15 still logged in
reboot system boot 2.6.32-504.el6.x Wed Aug 19 23:15 - 00:12 (00:56)
【查看某用户】
当登陆系统用户很多的时候，可以在w后面加上某个用户名，则会查看该用户执行任务的情况
[root@test1 ~]# w lxh 00:21:08 up 1:06, 2 users, load average: 0.00, 0.00, 0.00 USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT lxh pts/0 192.168.150.1 00:10 0.00s 0.03s 0.02s sshd: lxh [priv]
【查看进程】
[root@test1 ~]# ps -ef | grep sshd root 927 1 0 Aug19 ? 00:00:00 /usr/sbin/sshd root 1905 927 0 00:10 ? 00:00:00 sshd: lxh [priv] lxh 1908 1905 0 00:10 ? 00:00:00 sshd: lxh@pts/0 root 2047 1946 0 00:22 pts/0 00:00:00 grep --color=auto sshd [root@test1 ~]# ps aux | grep sshd root 927 0.0 0.1 66688 1216 ? Ss Aug19 0:00 /usr/sbin/sshd root 1905 0.0 0.4 98376 4228 ? Ss 00:10 0:00 sshd: lxh [priv] lxh 1908 0.0 0.1 98376 1936 ? S 00:10 0:00 sshd: lxh@pts/0 root 2057 0.0 0.0 103260 844 pts/0 S+ 00:23 0:00 grep --color=auto sshd
原文：http://xoyabc.blog.51cto.com/7401264/1686251