Linux基础-用户相关

getent

getent is a common way to look up in user details on Linux;
getent is a Linux command that helps the user to get the entries in a number of important text files called databases;

Supported databases:

1. passwd shadow
2. group gshadow
2. ahosts ahostsv4 ahostsv6
2. aliases ethers 
4. hosts initgroups
2. netgroup networks  protocols rpc services 

Usage:
getent [OPTION...] database [key ...]

用户相关文件

/etc/passwd--

格式：
login_name：passwd(x)：UID：GID：GECOS：home_directory：shell

/etc/shadow--

格式：
login_name:passwd(sha512):
从1970.01.01起到密码最近一次被修改的时间：
密码再过几天可以被变更(0-任意)：
密码再过几天必须被变更：
密码过期前几天系统提醒用户（默认7天）：
密码过期几天后账号被锁定：
从1970.01.01算起，多少天后账号失效

/etc/group
/etc/gshadow

用户相关命令

useradd

useradd [OPTIONS] LOGIN
useradd -D -- 默认配置/etc/default/useradd

newusers -- update and create new users in batch

newusers [options] format_files
pw_name:pw_passwd:pw_uid:pw_gid:pw_gecos:pw_dir:pw_shell

su和sudo的区别

su -- Change the effective user id and group id to that of USER. A mere - implies -l. If USER not given, assume root.

su [options] [-] [USER [arg]...]

sudo -- execute a command as another user

sudo [options] [<command>]
sudo -i -- run login shell as the target user
sudo -s -- run shell as the target user;

Different:

1. -The main difference between the two is that su requires the password of the target account, while sudo requires the password of the current user.
2. -Additionally，it is advisable to stick to sudo when performing tasks that require root privileges. By doing so, the current user is only granted privileged for the specified command.