pwconv
功能说明：开启用户的投影密码。
语法：pwconv
补充说明：Linux系统里的用户和群组密码，分别存放在名称为passwd和group的文件中，这两个文件位于/etc目录下。因系统运作所需，任何人都得以读取它们，造成安全上的破绽。投影密码将文件内的密码改存在/etc目录下的shadow和gshadow文件内，只允许系统管理者读取，同时把原密码置换为"x"字符，有效的强化了系统的安全性。
#p#
NAME
pwconv, pwunconv, grpconv, grpunconv - convert to and from shadow passwords and groups.
SYNOPSIS
pwconv
pwunconv
grpconv
grpunconv
DESCRIPTION
These four programs all operate on the normal and shadow password and group files: /etc/passwd, /etc/group, /etc/shadow, and /etc/gshadow.
pwconv creates shadow from passwd and an optionally existing shadow. pwunconv creates passwd from passwd and shadow and then removes shadow. grpconv creates gshadow from group and an optionally existing gshadow. grpunconv creates group from group and gshadow and then removes gshadow.
Each program acquires the necessary locks before conversion.
pwconv and grpconv are similiar. First, entries in the shadowed file which don't exist in the main file are removed. Then, shadowed entries which don't have `x' as the password in the main file are updated. Any missing shadowed entries are added. Finally, passwords in the main file are replaced with `x'. These programs can be used for initial conversion as well to update the shadowed file if the main file is edited by hand.
pwconv will use the values of PASS_MIN_DAYS, PASS_MAX_DAYS, and PASS_WARN_AGE from /etc/login.defs when adding new entries to /etc/shadow.
Likewise, pwunconv and grpunconv are similiar. Passwords in the main file are updated from the shadowed file. Entries which exist in the main file but not in the shadowed file are left alone. Finally, the shadowed file is removed.
Some password aging information is lost by pwunconv. It will convert what it can.
BUGS
Errors in the password or group files (such as invalid or duplicate entries) may cause these programs to loop forever or fail in other strange ways. Please run pwck and grpck to correct any such errors before converting to or from shadow passwords or groups.
SEE ALSO
login.defs(5), grpck(8), pwck(8)
