嵌入式linux开发，启用用户登录功能

        在嵌入式linux开发中，由busybox生成的文件系统，默认是没有用户登录的，如下：

~ #

        启用用户登录，方法如下：

Login/Password Management Utilities --->
    [*]  getty
    [*]  login
    []  Run logged in session in a child process
    []  Support for PAM (Pluggable Authentication Modules)
    [*]  Support for login scripts
    [*]  Support for /etc/nologin
    [*]  Support for /etc/securetty
    [*]  passwd
    [*]  Check new passwords for weakness

root:x:0:
daemon:x:1:
bin:x:2:
sys:x:3:
adm:x:4:syslog,ms
tty:x:5:
disk:x:6:
lp:x:7:
mail:x:8:
news:x:9:
uucp:x:10:

root::0:0:root:/:/bin/sh（输完用户名，回车，直接进入用户）或root:K99ZQ9IohtbWU:0:0:root:/:/bin/sh（输完用户名，回车，进入密码输入，回车，进入用户）
daemon:x:1:1:daemon:/sbin:
bin:x:2:2:bin:/bin:
sys:x:3:3:sys:/dev:/usr/sbin/nologin
sync:x:4:65534:sync:/bin:/bin/sync
nobody:x:99:99:Nobody:/:/sbin/nologin
ftp:x:501:0:ftp:/var:/bin/sh
usb:x:504:100::/usb:

root::1:0:99999:7:::
daemon:*:18480:0:99999:7:::
bin:*:18480:0:99999:7:::
sys:*:18480:0:99999:7:::
sync:*:18480:0:99999:7:::
ftp:!:0::::::
usb:*:13941::::::

::sysinit:/etc/init.d/rcS
console::askfirst:-/bin/login
::ctrlaltdel:/sbin/reboot
::shutdown:/sbin/swapoff -a
::shutdown:/bin/umount -a -r
::restart:/sbin/init

         直接进入，不需要输入用户名和密码，配置如下：

#::once:-/bin/sh
console::askfirst:-/bin/sh

        需要输入登录信息，配置如下：

#::once:-/bin/sh
console::askfirst:-/bin/login

# /etc/inittab init(8) configuration for BusyBox
#
# Copyright (C) 1999-2004 by Erik Andersen 
#
#
# Note, BusyBox init doesn't support runlevels.  The runlevels field is
# completely ignored by BusyBox init. If you want runlevels, use sysvinit.
#
#
# Format for each entry: :::
#
# : WARNING: This field has a non-traditional meaning for BusyBox init!
#
#       The id field is used by BusyBox init to specify the controlling tty for
#       the specified process to run on.  The contents of this field are
#       appended to "/dev/" and used as-is.  There is no need for this field to
#       be unique, although if it isn't you may have strange results.  If this
#       field is left blank, it is completely ignored.  Also note that if
#       BusyBox detects that a serial console is in use, then all entries
#       containing non-empty id fields will be ignored.  BusyBox init does
#       nothing with utmp.  We don't need no stinkin' utmp.
#
# : The runlevels field is completely ignored.
#
# : Valid actions include: sysinit, respawn, askfirst, wait, once,
#                                  restart, ctrlaltdel, and shutdown.
#
#       Note: askfirst acts just like respawn, but before running the specified
#       process it displays the line "Please press Enter to activate this
#       console." and then waits for the user to press enter before starting
#       the specified process.
#
#       Note: unrecognised actions (like initdefault) will cause init to emit
#       an error message, and then go along with its business.
#
# : Specifies the process to be executed and it's command line.
#
# Note: BusyBox init works just fine without an inittab. If no inittab is
# found, it has the following default behavior:
#         ::sysinit:/etc/init.d/rcS
#         ::askfirst:/bin/sh
#         ::ctrlaltdel:/sbin/reboot
#         ::shutdown:/sbin/swapoff -a
#         ::shutdown:/bin/umount -a -r
#         ::restart:/sbin/init
#
# if it detects that /dev/console is _not_ a serial console, it will
# also run:
#         tty2::askfirst:/bin/sh
#         tty3::askfirst:/bin/sh
#         tty4::askfirst:/bin/sh
#
# Boot-time system configuration/initialization script.
# This is run first except when booting in single-user mode.
#
::sysinit:/etc/init.d/rcS

# /bin/sh invocations on selected ttys
#
# Note below that we prefix the shell commands with a "-" to indicate to the
# shell that it is supposed to be a login shell.  Normally this is handled by
# login, but since we are bypassing login in this case, BusyBox lets you do
# this yourself...
#
# Start an "askfirst" shell on the console (whatever that may be)
#::once:-/bin/sh
console::askfirst:-/bin/login
# Start an "askfirst" shell on /dev/tty2-4
#tty2::askfirst:-/bin/sh
#tty3::askfirst:-/bin/sh
#tty4::askfirst:-/bin/sh

# /sbin/getty invocations for selected ttys
#tty4::respawn:/sbin/getty 38400 tty5
#tty5::respawn:/sbin/getty 38400 tty6

# Example of how to put a getty on a serial line (for a terminal)
#::respawn:/sbin/getty -L ttyS0 9600 vt100
#::respawn:/sbin/getty -L ttyS1 9600 vt100
#
# Example how to put a getty on a modem line.
#::respawn:/sbin/getty 57600 ttyS2

# Stuff to do when restarting the init process
::restart:/sbin/init

# Stuff to do before rebooting
::ctrlaltdel:/sbin/reboot
::shutdown:/bin/umount -a -r
::shutdown:/sbin/swapoff -a