[root@bogon ~]# useradd --help  
Usage: useradd [options] LOGIN  
  
Options:  
  -b, --base-dir BASE_DIR       base directory for the home directory of the  
                                new account  
  -c, --comment COMMENT         GECOS field of the new account  
  -d, --home-dir HOME_DIR       home directory of the new account  
  -D, --defaults                print or change default useradd configuration  
  -e, --expiredate EXPIRE_DATE  expiration date of the new account  
  -f, --inactive INACTIVE       password inactivity period of the new account  
  -g, --gid GROUP               name or ID of the primary group of the new  
                                account  
  -G, --groups GROUPS           list of supplementary groups of the new  
                                account  
  -h, --help                    display this help message and exit  
  -k, --skel SKEL_DIR           use this alternative skeleton directory  
  -K, --key KEY=VALUE           override /etc/login.defs defaults  
  -l, --no-log-init             do not add the user to the lastlog and  
                                faillog databases  
  -m, --create-home             create the user's home directory  
  -M, --no-create-home          do not create the user's home directory  
  -N, --no-user-group           do not create a group with the same name as  
                                the user  
  -o, --non-unique              allow to create users with duplicate  
                                (non-unique) UID  
  -p, --password PASSWORD       encrypted password of the new account  
  -r, --system                  create a system account  
  -s, --shell SHELL             login shell of the new account  
  -u, --uid UID                 user ID of the new account  
  -U, --user-group              create a group with the same name as the user  
  -Z, --selinux-user SEUSER     use a specific SEUSER for the SELinux user mapping 

useradd -c "This user cannot login to a shell" -s /sbin/nologin username  
#添加用户，但是不能登入shell  
useradd -c "This user login by bash" -s /bin/bash username  
#添加用户登入用后环境是bash  
useradd -d /usr/username  username  
#添加用户并指定加目录，默认是/home下面  
useradd -s /bin/sh -g group -G adm,root gem  
#添加用户指定shell,主组是group,从组是adm，root,gem 

[root@bogon ~]# userdel --help  
Usage: userdel [options] LOGIN  
  
Options:  
  -f, --force                   force removal of files,  
                                even if not owned by user  
  -h, --help                    display this help message and exit  
  -r, --remove                  remove home directory and mail spool  
  -Z, --selinux-user            remove SELinux user from SELinux user mapping 

userdel username  
#删除用户(passwd ,shadow)，但是不会删除该用户的家目录  
userdel -r username  
#删除用户，包括家目录 

[root@bogon ~]# usermod --help  
Usage: usermod [options] LOGIN  
  
Options:  
  -c, --comment COMMENT         new value of the GECOS field  
  -d, --home HOME_DIR           new home directory for the user account  
  -e, --expiredate EXPIRE_DATE  set account expiration date to EXPIRE_DATE  
  -f, --inactive INACTIVE       set password inactive after expiration  
                                to INACTIVE  
  -g, --gid GROUP               force use GROUP as new primary group  
  -G, --groups GROUPS           new list of supplementary GROUPS  
  -a, --append                  append the user to the supplemental GROUPS  
                                mentioned by the -G option without removing  
                                him/her from other groups  
  -h, --help                    display this help message and exit  
  -l, --login NEW_LOGIN         new value of the login name  
  -L, --lock                    lock the user account  
  -m, --move-home               move contents of the home directory to the  
                                new location (use only with -d)  
  -o, --non-unique              allow using duplicate (non-unique) UID  
  -p, --password PASSWORD       use encrypted password for the new password  
  -s, --shell SHELL             new login shell for the user account  
  -u, --uid UID                 new UID for the user account  
  -U, --unlock                  unlock the user account  
  -Z, --selinux-user            new SELinux user mapping for the user account 

usermod -d /usr/tttt -m tttt  
#移动家目录到/usr/tttt  
usermod -d /usr/tttt tttt  
#修改家目录到/user/tttt，原来的/home/tttt还保留  
usermod -s /bin/ksh -d /home/z -g developer sam  
#用户sam的登录Shell修改为ksh，主目录改为/home/z，用户组改为developer 

finger , id 
NAME  
     finger - user information lookup program  
SYNOPSIS  
     finger [-lmsp] [user ...] [user@host ...]  
DESCRIPTION  
     The finger displays information about the system users. 

finger 用户名 ----可以查看用户的相关信息，包括用户的主目录，启动shell，用户名等 
finger -l 用户名----以长格式显示用户信息 
finger -s 用户名 ----以短格式显示用户信息

[root@bogon srv]# finger spark  
Login: spark                            Name: Spark  
Directory: /home/spark                  Shell: /bin/bash  
On since Tue Jul 15 16:56 (CST) on tty1 from :0  
   23 days 18 hours idle  
No mail.  
No Plan. 

[root@bogon srv]# id --help  
Usage: id [OPTION]... [USERNAME]  
Print user and group information for the specified USERNAME,  
or (when USERNAME omitted) for the current user.  
  
  -a              ignore, for compatibility with other versions  
  -Z, --context   print only the security context of the current user  
  -g, --group     print only the effective group ID  
  -G, --groups    print all group IDs  
  -n, --name      print a name instead of a number, for -ugG  
  -r, --real      print the real ID instead of the effective ID, with -ugG  
  -u, --user      print only the effective user ID  
      --help     display this help and exit  
      --version  output version information and exit