System information

Tips and Techniques: Install and Configure Oracle9i on Red Hat Linux
Advanced Server
Certain files and tools provide good starting point for analyzing the state of the
system. /var/log/messages is one of them.
For problems related to loading drivers,
dmesg , lspci and lsmod are very useful.
Utilities like
strace and ltrace are also available.
Other than these small utilities, there are the other debugging tools and techniques
available, that would help in analyzing the system, even after it has hung or crashed
completely. They are
a) use of magic sysrq keys
b) serial console.
c) Netdump utility
In all these cases, as was discussed before, the value of /proc/sys/kernel/sysrq
should be set to 1.
Magic sysrq keys
Even in case of hang or crash, user could still collect system information. User
could use magic sysrq keys. A key sequence is to be pressed for collecting some
information or performing a specific task. The sequence is “alt”, “sysrq” and any of
following magic keys.
A table follows that lists the Magic sysrq key and the corresponding functionality.
Functionality Magic sysrq key
sync data to disks s
remount partitions read only u
reboot the machine b
power the machine off o
turns off keyboard raw mode and puts it
in XLATE
r
dump the cpu registers and flags p
list tasks and some useful information
about them
t
kills a process on the current console k
send SIGTERM to everything except
init
e
send SIGKILL to everything except init i
Tips and Techniques: Install and Configure Oracle9i on Red Hat Linux Advanced Server Page 17