administration command. Convert unshadowed entries in /etc/passwd
into shadowed entries in the /etc/shadow file.
Replace the encrypted password in /etc/password with an x.
Shadowing passwords keeps them safe from password cracking programs. pwconv creates additional expiration information
for the /etc/shadow file from entries in your /etc/login.defs
file. If you add new entries to the /etc/passwd file, you
can run pwconv again to transfer the new information to /etc/shadow.
Already shadowed entries are ignored. pwunconv
restores the encrypted passwords to your /etc/passwd file and
removes the /etc/shadow file. Some expiration information
is lost in the conversion.