1.用户组

添加组：groupadd 组名

[root@ecs-6ba4-0001 /]# groupadd dev
[root@ecs-6ba4-0001 /]# cat /etc/group | grep dev
dev:x:1000:
[root@ecs-6ba4-0001 /]# 

删除组：groupdel 组名

[root@ecs-6ba4-0001 /]# groupdel dev
[root@ecs-6ba4-0001 /]# cat /etc/group | grep dev
[root@ecs-6ba4-0001 /]# 

查询组：cat /etc/group 或者使用管道来精确查询 cat /etc/group | grep dev

[root@ecs-6ba4-0001 /]# cat /etc/group
root:x:0:
bin:x:1:
daemon:x:2:
sys:x:3:
adm:x:4:
tty:x:5:
disk:x:6:
lp:x:7:
mem:x:8:
kmem:x:9:
wheel:x:10:
cdrom:x:11:
mail:x:12:postfix
man:x:15:
dialout:x:18:
floppy:x:19:
games:x:20:
tape:x:33:
video:x:39:
ftp:x:50:
lock:x:54:
audio:x:63:
users:x:100:
nobody:x:65534:
dbus:x:81:
utmp:x:22:
utempter:x:35:
input:x:999:
kvm:x:36:
render:x:998:
systemd-journal:x:190:
systemd-coredump:x:997:
systemd-resolve:x:193:
tss:x:59:
polkitd:x:996:
unbound:x:995:
postdrop:x:90:
postfix:x:89:
ssh_keys:x:994:
sssd:x:993:
sshd:x:74:
chrony:x:992:
rngd:x:991:
tcpdump:x:72:
dev:x:1000:
[root@ecs-6ba4-0001 /]# 

 /etc 目录是专门用来保存 系统配置信息 的目录

 group 是保存组信息的文件

2.用户

添加用户：useradd -m -g 组 新建用户名            注意：-m 自动建立用户家目录； -g 指定用户所在的组，否则会建立一个和用户名同名的组

[root@ecs-6ba4-0001 /]# useradd -m -g dev test1
[root@ecs-6ba4-0001 /]# 

dev为用户组，test1为用户名

查询用户：在/etc/passwd文件下存储的是用户的list

[root@ecs-6ba4-0001 /]# cat /etc/passwd
root:x:0:0:root:/root:/bin/bash
bin:x:1:1:bin:/bin:/sbin/nologin
daemon:x:2:2:daemon:/sbin:/sbin/nologin
adm:x:3:4:adm:/var/adm:/sbin/nologin
lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
sync:x:5:0:sync:/sbin:/bin/sync
shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
halt:x:7:0:halt:/sbin:/sbin/halt
mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
operator:x:11:0:operator:/root:/sbin/nologin
games:x:12:100:games:/usr/games:/sbin/nologin
ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin
nobody:x:65534:65534:Kernel Overflow User:/:/sbin/nologin
dbus:x:81:81:System message bus:/:/sbin/nologin
systemd-coredump:x:999:997:systemd Core Dumper:/:/sbin/nologin
systemd-resolve:x:193:193:systemd Resolver:/:/sbin/nologin
tss:x:59:59:Account used by the trousers package to sandbox the tcsd daemon:/dev/null:/sbin/nologin
polkitd:x:998:996:User for polkitd:/:/sbin/nologin
unbound:x:997:995:Unbound DNS resolver:/etc/unbound:/sbin/nologin
postfix:x:89:89::/var/spool/postfix:/sbin/nologin
sssd:x:996:993:User for sssd:/:/sbin/nologin
sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin
chrony:x:995:992::/var/lib/chrony:/sbin/nologin
rngd:x:994:991:Random Number Generator Daemon:/var/lib/rngd:/sbin/nologin
tcpdump:x:72:72::/:/sbin/nologin
test1:x:1000:1000::/home/userone:/bin/bash
[root@ecs-6ba4-0001 /]# 

只查找test1用户

[root@ecs-6ba4-0001 /]# id test1
uid=1000(test1) gid=1000(dev) groups=1000(dev)
[root@ecs-6ba4-0001 /]# 

uid为用户id,  gid为组id

修改和创建密码 passwd 用户名    如果不加用户名则默认修改当前登录者的密码

 [root@ecs-6ba4-0001 /]# passwd test1
Changing password for user test1.
New password:
Retype new password:
passwd: all authentication tokens updated successfully.
[root@ecs-6ba4-0001 /]#

设置好密码后，使用此账号和密码登录

➜  ~ ssh test1@192.168.85.163
test1@192.168.85.163's password:
Last failed login: Mon Jul 22 17:00:05 CST 2019 from 192.168.1.53 on ssh:notty
There were 3 failed login attempts since the last successful login.
[test1@Server-n93yom ~]$

设置用户不能修改密码

[root@Server-n93yom ~]# passwd -l test1     //在root下，禁止test1用户修改密码的权限
Locking password for user test1.            //锁住test1不能修改密码
passwd: Success
[root@Server-n93yom ~]# su test1            //切换用户
[test1@Server-n93yom root]$ passwd          //修改密码
Changing password for user test1.
Changing password for test1.
(current) UNIX password:
passwd: Authentication token manipulation error  //没用权限修改密码
[test1@Server-n93yom root]$

清除密码

[root@Server-n93yom ~]# passwd -d test1    //删除test1的密码
Removing password for user test1.
passwd: Success
[root@Server-n93yom ~]# passwd -S test1     //查看test1的密码
test1 NP 2019-07-22 0 99999 7 -1 (Empty password.)   //密码为空
[root@Server-n93yom ~]#

passwd 帮助命令

[root@Server-n93yom ~]# passwd --help
Usage: passwd [OPTION...] <accountName>
  -k, --keep-tokens       keep non-expired authentication tokens
  -d, --delete            delete the password for the named account (root only)
  -l, --lock              lock the password for the named account (root only)
  -u, --unlock            unlock the password for the named account (root only)
  -e, --expire            expire the password for the named account (root only)
  -f, --force             force operation
  -x, --maximum=DAYS      maximum password lifetime (root only)
  -n, --minimum=DAYS      minimum password lifetime (root only)
  -w, --warning=DAYS      number of days warning users receives before password
                          expiration (root only)
  -i, --inactive=DAYS     number of days after password expiration when an account
                          becomes disabled (root only)
  -S, --status            report password status on the named account (root only)
  --stdin                 read new tokens from stdin (root only)

Help options:
  -?, --help              Show this help message
  --usage                 Display brief usage message
[root@Server-n93yom ~]#

3.设置密码失效时间

可以编辑/etc/login.defs来设定几个参数，以后设置口令默认就按照参数设定为准：

PASS_MAX_DAYS   99999
PASS_MIN_DAYS   0
PASS_MIN_LEN    5
PASS_WARN_AGE   7

当然在/etc/default/useradd可以找到如下2个参数进行设置：

# useradd defaults file
GROUP=100
HOME=/home
INACTIVE=-1
EXPIRE=
SHELL=/bin/bash
SKEL=/etc/skel
CREATE_MAIL_SPOOL=yes

通过修改配置文件，能对之后新建用户起作用，而目前系统已经存在的用户，则直接用chage来配置。

chage [选项] 用户名

chage命令是用来修改帐号和密码的有效期限。

-m：密码可更改的最小天数。为零时代表任何时候都可以更改密码。
-M：密码保持有效的最大天数。
-w：用户密码到期前，提前收到警告信息的天数。
-E：帐号到期的日期。过了这天，此帐号将不可用。
-d：上一次更改的日期。
-i：停滞时期。如果一个密码已过期这些天，那么此帐号将不可用。
-l：例出当前的设置。由非特权用户来确定他们的密码或帐号何时过期。

chage -l root 查root账号的信息

[root@Server-n93yom ~]# chage -l root
Last password change                    : Jul 22, 2019
Password expires                    : never
Password inactive                    : never
Account expires                        : never
Minimum number of days between password change        : 0
Maximum number of days between password change        : 99999
Number of days of warning before password expires    : 7
[root@Server-n93yom ~]#

chage -M 60 test  设置密码过期时间为60天
chage -I 5 test    设置密码失效时间为5天

以test1账号为例，再查一次信息账号信息

[root@Server-n93yom ~]# chage -l test1
Last password change                    : Jul 22, 2019
Password expires                    : Sep 20, 2019
Password inactive                    : Sep 25, 2019
Account expires                        : never
Minimum number of days between password change        : 0
Maximum number of days between password change        : 60
Number of days of warning before password expires    : 7

从上述命令可以看到，在密码过期后5天，密码自动失效，这个用户将无法登陆系统了。