Specifications

A-16
Cisco TV CDS 2.5 ISA Software Configuration Guide
OL-24788-01
Appendix A Troubleshooting
General Information and Issues
Kernel Crash
The kernel debugger (KDB) provides information (in the form of a core dump file) when the server
processing fails. For the server to enter KDB when the server has crashed, the /proc/sys/kernel/panic
parameter must be zero. If the panic parameter is non-zero, the system reboots automatically without
entering KDB.
In addition to KDB, there is a kdump service. The kdump service allows you to take a kernel dump of
memory. The kdump service runs automatically if the server is configured to reboot automatically after
a crash (which means the panic parameter is non-zero). The kdump service stores the kernel memory
dump in the /var/arroyo/crash directory. After the kernel memory is dumped, the system reboots into the
normal operating system.
If the server is configured to enter KDB (which means the panic parameter is zero), the server enters
KDB mode. The kdump command allows you to take a kernel memory dump while the server is in KDB
mode. The kdump command reboots the server into kdump mode, takes a kernel memory dump, and
reboots the server into the normal operating system.
If a server has crashed after being started automatically from the /etc/rc.local directory, you need to boot
in single-user mode. To boot in single-user mode, perform the following steps:
Step 1 Reboot the server.
Step 2 When a blue screen displays a list of Linux versions, press the E key to edit the kernel entry.
Step 3 Multiple lines are displayed. Use the Up Arrow and Down Arrow keys to highlight the second line. You
may need to press the E key again to edit the line. A square cursor appears at the end of the line.
Step 4 Remove the 115200 from the console parameter (for example, console=ttySO,115200n8).
Step 5 Add the word “Single” or the letter “S” to the end of the line.
Step 6 Press Enter.
Step 7 Press the B key to boot the Linux kernel into single-user mode.
Step 8 Wait for the server to finish booting up.
Step 9 Edit the /etc/rc.local file and comment out the line /arroyo/test/vault/run.
Step 10 Reboot the server.
To view the contents of the core dump file from the Linux prompt, do the following:
Step 1 Run the GNU debugger (gdb), and specify the core file and binary file.
gdb --core=<core-file> <binary-file>
The core-file parameter is the core filename and the binary-file is the binary file that produced the core
file.
Step 2 After the GNU debugger has started, enter the backtrace command, bt, at the gdb prompt and press
Enter.
gdb> bt
The callback stack is displayed, which shows the history of the current function calls that were made at
the time of the crash.