What to do if the system does not boot

There are several scenarios in which modifications or damage to the system may result in a system that does not boot:

• hardware failure

• modification to the system kernel; for example, an adjustment to a tunable parameter, or installation or the removal of system software, such as a device driver

• removal of a file or system utility needed by the system during the boot phase

After the system kernel is modified, either as a result of software installation/removal or adjustment to a tunable parameter, a copy of the old kernel is automatically saved in the file /stand/unix.old.

Some administrators like to keep a copy of a kernel that they know to be bootable under another name, unix.good, for example. If you provide the name of that kernel, the boot code will load that kernel.

Before you make any further kernel modifications, make sure that you have saved this good kernel in /stand under a name different than unix.old since the next kernel build will cause the current (non-functional) unix kernel to be saved as unix.old at the next reboot.

To recover from a new, unbootable kernel, first try to reboot the old system kernel (boot your system using the kernel saved at the system reboot after rebuilding your kernel):

1. Start the reboot process through one of the following methods (listed in order of preference):

   • Press the <Ctrl>, <Alt>, and <Del> keys simultaneously.

   • Press the <RESET> button on your computer.

   • Turn the power switch off and then back on.

2. When you see this message:

   The system is coming up.  Please wait.
   

   or the UnixWare logo screen, press <Space>.

3. When you see the BCP prompt, [boot], type:

      boot unix.old
   

   or some other kernel saved under a different name.

If this procedure fails or is not possible because of a failure in saving unix.old during a kernel reboot, or if you believe the system is failing to boot because of deleted or corrupted files, use the emergency recovery diskette to manually repair your system, or to restore data from emergency recovery tapes. See the topic ``Recovering your system'' in the Getting Started Guide for details.