1.列出当前系统上所有已经登录的用户的用户名，注意：同一个用户登录多次，则只显示一次即可
[root@foundation0 ~]# who | cut -d ' ' -f 1 | sort -u
root
jin
2.取出最后登录到当前系统的用户的相关信息
[jin@foundation0 ~]$ who | sort -r -k 3 | head -n 1 > /tmp/haha.txt
[jin@foundation0 ~]$ cat /tmp/haha.txt
jin pts/5 2016-10-5 12:05 (192.168.0.100)
3.取出当前系统上被用户当作其默认shell的最多的那个shell
[jin@foundation0 ~]$ cut -d: -f /etc/passwd | sort | uniq -c | sort -f | tail -n 1 > /tmp/sh
[jin@foundation0 ~]$ cat /tmp/shell.txt
39 /sbin/nologin
4.将/etc/passwd 中的第三个字段数值最大的后10个用户的信息全部改为大写后保存至/tmp/maxusers.txt文件中
[jin@foundation0 ~]$ sort -t : -k 3 -n /etc/passwd | tail -n 10 | tr [a-z] [A-Z] > /tmp/maxus
[jin@foundation0 ~]$ cat /tmp/maxusers.txt
5.取出当前主机的IP地址，提示：对ifconfig命令的结果进行切分
[jin@foundation0 ~]$ ifconfig eno16777736 | grep -w " inet" | cut -d ' ' -f 10
192.168.0.100
6.列出/etc目录下所有以.conf结尾的文件的文件名，并将其名字转换为大写后保存至/tmp/etc.conf文件中
[root@foundation0 ~]# ls /etc/ |grep '.conf$' > /tmp/etc.conf
[root@foundation0 ~]# cat /tmp/etc.conf
asound.conf
autofs.conf
autofs_ldap_auth.conf
brltty.conf
cgconfig.conf
cgrules.conf
cgsnapshot_blacklist.conf
chrony.conf
dleyna-server-service.conf
dnsmasq.conf
dracut.conf
e2fsck.conf
fprintd.conf
fuse.conf
hba.conf
host.conf
idmapd.conf
ipsec.conf
kdump.conf
krb5.conf
ksmtuned.conf
ld.so.conf
libaudit.conf
libuser.conf
locale.conf
logrotate.conf
man_db.conf
mke2fs.conf
mtools.conf
nfsmount.conf
nsswitch.conf
ntp.conf
numad.conf
oddjobd.conf
pbm2ppa.conf
pnm2ppa.conf
radvd.conf
request-key.conf
resolv.conf
rsyncd.conf
rsyslog.conf
sestatus.conf
sos.conf
sudo.conf
sudo-ldap.conf
sysctl.conf
tcsd.conf
updatedb.conf
usb_modeswitch.conf
vconsole.conf
wvdial.conf
7.显示/var目录下一级子目录或文件的总个数
[root@foundation0 ~]# 11 -a /var/ | wc -1
26
8.取出/etc/group文件中第三个字段数值最小的10个组的名字
[jin@foundation0 ~]$ cat /etc/group | sort -t: -k 3 -n -r | tail -n 10
kmem:x:9:
mem:x:8:
lp:x:7:
disk:x:6:
tty:x:5:
adm:x:4:
sys:x:3:
daemon:x:2:
bin:x:1:
root:x:0:
9.将/etc/fstab和/etc/issue文件的内容合并为同一个内容后保存至/tmp/etc.test文件中
[jin@foundation0 ~]$ cat /etc/fstab /etc/issue > /tmp/etc.test
[jin@foundation0 ~]$ cat /tmp/etc.test
10.请总结描述用户和组管理类命令的使用方法并完成以下练习：
(1)、创建组distro，其GID为2016
[root@foundation0 ~]# groupadd -g 2016 distro
(2)、创建用户mandriva, 其ID号为1005；基本组为distro
[root@foundation0 ~]# useradd -u 1005 -g distro mandriva
(3)、创建用户mageia，其ID号为1100，家目录为/home/linux
[root@foundation0 ~]# useradd -u 1100 -d /home/linux mageia
(4)、给用户mageia添加密码，密码为redhat
[root@foundation0 ~]# passwd mageia
Changing password for user mageia.
New password:
BAD PASSWORD: The password is shorter than 8 characters
Retype new password:
passwd: all authentication tokens updated successfully
(5)、删除mandriva，但保留其家目录
[root@foundation0 ~]# userdel mandriva
(6)、创建用户slackware，其ID号为2002，基本组为distro，附加组peguin
[root@foundation0 ~]# groupadd peguin
[root@foundation0 ~]# useradd -u 2002 -g distro -G peguin slackware
[root@foundation0 ~]# id slackware
uid=2002(slackware) gid=2016(distro) groups=2016(distro),2017(peguin)
(7)、修改slackware的默认shell为/bin/tcsh
[root@foundation0 home]# usermod -s /bin/tcsh slackware
[root@foundation0 home]# tail -n 1 /etc/passwd
slackware:x:2002:2016::/home/slackware:/bin/tcsh
(8)、为用户slackware新增附加组admins
[root@foundation0 ~]# usermod -a -G admins slackware
[root@foundation0 ~]# id slackware
(9)、为slackware添加密码，且要求密码最短使用期限为3天，最长为180天，警告为3天
[root@foundation0 ~]# # passwd redhat | passwd slackware -n 3 -x 180 -w 3
Adjusting aging data for user slackware.
passwd: Success
New password:
BAD PASSWORD: The password is shorter than 7 characters
Retype new password:
[root@localhost jun_shao]# tail -n 1 /etc/shadow
slackware:$6$6SP2wfD/$9OyF6m0WBSnB/QvMeKcy/Qaa494ctEDVDWX2jktapof..6Ud.yCEnkPE3bYUWfr20wy6DWdIU6x1FIoum6Kd20:17033:3:180:3:::
(10)、添加用户openstack，其ID号为3003, 基本组为clouds，附加组为peguin和nova
[root@foundation0 ~]# useradd -u 3003 -g clouds -G peguin,nova openstack
[root@foundation0 ~]# id openstack
uid=3003(openstack)gid=2019(clouds)groups=2019(clouds),2017(peguin),2020(nova)
(11)、添加系统用户mysql，要求其shell为/sbin/nologin
[root@foundation0 ~]# useradd -r -s /sbin/nologin mysq1
[root@foundation0 ~]# tail -n 1 /etc/passwd
mysql:x:987:982::/home/mysql:/sbin/nologin
(12)、使用echo命令，非交互式为openstack添加密码
[root@foundation0 ~]# echo "redhat" | passwd --stdin openstack
