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unix user

The Art of Unix Programming by Eric Raymond is a book about the history and culture of Unix programming from its earliest days in 1969 to now, covering both genetic derivations such as BSD and conceptual ones such as Linux.

You should read this book if you are an experienced Unix programmer who is often in the position of either educating novice programmers or debating partisans of other operating systems, and you find it hard to articulate the benefits of the Unix approach.

You should read this book if you are a C, C++, or Java programmer with experience on other operating systems and you are about to start a Unix-based project.

You should read this book if you are a Unix user with novice-level up to middle-level skills in the operating system, but little development experience, and want to learn how to design software effectively under Unix.

You can read HTML version of "The Art of Unix Programming" online at Eric's website.

For security, reason it is necessary to disable all account(s) with no password and lock them down. Solaris, Linux and FreeBSD provide account locking (unlocking) facility.

Lock Linux user account with the following command:

passwd -l {user-name}

For unlocking the account use:

passwd  -u {user-name}

-l : This option disables an account by changing the password to a value, which matches no possible encrypted value.

Lock FreeBSD user account with the following command:

pw lock {username}

FreeBSD unlocking the account use:

pw unlock {username}

Lock Solaris UNIX user account with the following command:

passwd -l {username}

Lock HP-UX user account with the following command:

passwd -l {username}

For unlocking the HP-UX account you need to edit /etc/passwd file using text editor (or use SAM):

vi /etc/passwd 

However, how will you find out account without password? Again, with the help of 'passwd -s' (status) command you can find out all passwordless accounts.

Linux display password status

passwd -S {user-name}

Where,
-S : Display account status information. The status information consists of total seven fields. The second field indicates the status of password using following format:

  • L : if the user account is locked (L)
  • NP : Account has no password (NP)
  • P: Account has a usable password (P)
# passwd -S radmin

radmin P 10/08/2005 0 99999 7 -1

Solaris UNIX display password status

passwd -s {user-name}

Where,
-s : Display account status information using following format:

  • PS : Account has a usable password
  • LK : User account is locked
  • NP : Account has no password

FreeBSD
I have already written about small awk one line approach to find out all passwords less accounts.

Automated Scripting Solution
However, in real life you write a script and execute it from cron job. Here is small script for Linux:

#!/bin/sh
USERS="$(cut -d: -f 1 /etc/passwd)"
for u in $USERS
do
passwd -S $u | grep -Ew "NP" >/dev/null
if [ $? -eq 0 ]; then
passwd -l $u
fi
done

FreeBSD script:

#!/bin/bash
USERS="$(awk -F: 'NF > 1 && $1 !~ /^[#+-]/ && $2=="" {print $0}'
/etc/master.passwd | cut -d: -f1)"
for u in $USERS
do
pw lock $u
done

Sun Solaris script:

#!/bin/sh
USERS=`passwd -sa | grep -w NP | awk '{ print $1 }'`
for u in $USERS
do
passwd -l $u
done

You can easily add email alert support to script so that when ever scripts finds passwordless account(s) it will send an email alert. See the complete working example of script here.