Section 6.5. My Computer Won t Stop Rebooting

6.5. My Computer Won't Stop Rebooting

Newer Linux users are fascinated by the chance to experiment with different components. For the most part, careful experiments should be encouraged in a test environment. How else can we learn Linux? But there are mistakes that can annoy the heck out of us, including the Linux computer that won't stop rebooting.

Grouped in this section are three low-level annoyances associated with the boot process:

• The computer starts and then proceeds to shutdown without allowing a login.

• The computer starts and then proceeds to reboot, continuously.

• Something weird happens during the boot process.

These annoyances are normally associated with configuration problems in boot files. The first two of these annoyances are straightforward, as they relate to the default runlevel on your computer. In each of these cases, you'll almost certainly have to boot with a rescue disk or a system such as Knoppix, as described in the previous annoyance.

On occasion, these annoyances may be related to hardware issues. In those cases, you'll see similar behavior when you use a rescue disk or a system such as Knoppix to boot your system.

Red Hat has the elite certifications in the world of Linux, including that of the Red Hat Certified Engineer. One of the RHCE skills listed on the Red Hat web site suggests that RHCEs need to "diagnose and correct boot failures arising from bootloader, module, and filesystem errors." Does that sound like it addresses some of the annoyances in this chapter?

6.5.1. The Computer Starts and Then Shuts Down

This annoyance is often easy to fix. Once you've booted with a rescue disk and mounted the root directory (/), the first thing to check is the default runlevel as defined in /etc/inittab. If it's 0, as shown here, all you need to do is restore the proper default runlevel, such as 2 for Debian, or 3 or 5 for Red Hat/Fedora or SUSE:

 id:0:initdefault 

If the id directive isn't set to 0, you may have a different problem that's described later in this annoyance.

6.5.2. The Computer Starts and Then Reboots

This annoyance is also often straightforward. Again, boot with an appropriate rescue disk. Proceed by checking the default runlevel in /etc/inittab. If it's 6, as shown here, restore the proper default runlevel, such as 2 for Debian or 3 or 5 for Red Hat/Fedora or SUSE:

 id:6:initdefault 

If the id variable isn't set to 6, you may have a different problem described in the next section.

6.5.3. Something Weird Happens During the Boot Process

When Linux boots, it goes through more than just the /etc/inittab file. It reads the default runlevel and then starts the service scripts as defined in the associated /etc/rcx.d directory. While a problem here normally is associated with a configuration problem with a service, it's probably not serious.

If you want to add a program or script to the boot process, each distribution has a dedicated script in the /etc directory for this purpose.

Alternatively, most distributions have a user-definable script. You can use this script to add commands that you want applied to the computer during the boot process. For example, if you've configured a wireless network card using experimental code, you can add the command to start this card to the script. Various distributions define this script differently:

Red Hat/Fedora

Commands in the /etc/rc.local file run after all other init scripts.

SUSE

Commands in the /etc/init.d/boot.local file run after all other init scripts.

Debian

Debian Sarge includes a pointer to /etc/init.d/local in all runlevels. Interestingly enough, this file is missing from the default Debian configuration. But you can create it and add the commands that you need.