사용자 정보 (/etc/passwd)

$ cat /etc/passwd
# USERNAME : x : UID : GID : comment(description) : /home/dir : LOGIN_SHELL
# 두번째 x 필드 => 구 패스워드 필드
 
root:x:0:0:root:/root:/bin/bash
nobody:x:99:99:Nobody:/:/sbin/nologin
apache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin
jongpak:x:11000:11000:irteam sudo-account:/home/jongpak:/bin/bash

패드워드 정보 (/etc/shadow)

• https://www.tldp.org/LDP/lame/LAME/linux-admin-made-easy/shadow-file-formats.html
• https://www.cyberciti.biz/faq/understanding-etcshadow-file/
• https://unix.stackexchange.com/questions/252016/difference-between-vs-vs-in-etc-shadow
• https://stackoverflow.com/questions/24105498/what-do-and-mean-in-the-password-section-in-etc-shadow

$ sudo cat /etc/shadow
# USERNAME : 해시된패스워드 : 패스워드 최종변경일 (1970.01.01 이후 경과일) : 패스워드 변경 전 최소 사용가능기간 : 패드워드 변경전 최대 사용가능기간 : 패스워드변경 메시지 표시할 날짜 : 로그인접속 차단 일수 : 로그인 사용을 금지하는 일수 : 미사용
# 두번째 필드
#  $1$ is MD5
#  $2a$ is Blowfish
#  $2y$ is Blowfish
#  $5$ is SHA-256
#  $6$ is SHA-512
#  !! measns user account has not been initialed or has not been locked. Two exclamation points (!!) appear in the password field of the /etc/shadow file, which locks the account.
#  ! means group password is not available.
#  * means login disabled.
root:$6$eUjpxxxYAf.h$gz6GWQkz4FzDxxx0IsftQxxxxxxxx/:17966:0:99999:7:::
nobody:*:16372:0:99999:7:::
apache:!!:16659::::::
jongpak:!!:17511:90:99999:30:::