Книга: Embedded Linux Primer: A Practical, Real-World Approach

6.3.2. Example Web Server Startup Script

6.3.2. Example Web Server Startup Script

Although simple, this example startup script is designed to illustrate the mechanism and guide you in designing your own system startup and shutdown behavior. This example is based on busybox, which has a slightly different initialization behavior than init. These differences are covered in detail in Chapter 11.

In a typical embedded appliance that contains a web server, we might want several servers available for maintenance and remote access. In this example, we enable servers for HTTP and Telnet access (via inetd). Listing 6-8 contains a simple rc.sysinit script for our hypothetical web server appliance.

Listing 6-8. Web Server rc.sysinit

#!/bin/sh
echo "This is rc.sysinit"
busybox mount -t proc none /proc
# Load the system loggers
syslogd
klogd
# Enable legacy PTY support for telnetd
busybox mkdir /dev/pts
busybox mknod /dev/ptmx c 5 2
busybox mount -t devpts devpts /dev/pts

In this simple initialization script, we first enable the proc file system. The details of this useful subsystem are covered in Chapter 9. Next we enable the system loggers so that we can capture system information during operation. This is especially useful when things go wrong. The last entries enable support for the UNIX PTY subsystem, which is required for the implementation of the Telnet server used for this example.

Listing 6-9 contains the commands in the runlevel 2 startup script. This script contains the commands to enable any services we want to have operational for our appliance.

Listing 6-9. Example Runlevel 2 Startup Script

#!/bin/sh

echo "This is runlvl2.startup"

echo "Starting Internet Superserver"

inetd

echo "Starting web server"

webs &

Notice how simple this runlevel 2 startup script actually is. First we enable the so-called Internet superserver inetd, which intercepts and spawns services for common TCP/IP requests. In our example, we enabled Telnet services through a configuration file called /etc/inetd.conf. Then we execute the web server, here called webs. That's all there is to it. Although minimal, this is a working configuration for Telnet and web services.

To complete this configuration, you might supply a shutdown script (refer back to Listing 6-6), which, in this case, would terminate the web server and the Internet superserver before system shutdown. In our example scenario, that is sufficient for a clean shutdown.

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