System information

System Monitoring Utilities 19
2.2.4 Kernel Ring Buffer: dmesg
The Linux kernel keeps certain messages in a ring buffer. To view these messages,
enter the command dmesg:
tux@mercury:~> dmesg
[...]
end_request: I/O error, dev fd0, sector 0
subfs: unsuccessful attempt to mount media (256)
e100: eth0: e100_watchdog: link up, 100Mbps, half-duplex
NET: Registered protocol family 17
IA-32 Microcode Update Driver: v1.14 <[e-mail]>
microcode: CPU0 updated from revision 0xe to 0x2e, date = 08112004
IA-32 Microcode Update Driver v1.14 unregistered
bootsplash: status on console 0 changed to on
NET: Registered protocol family 10
Disabled Privacy Extensions on device c0326ea0(lo)
IPv6 over IPv4 tunneling driver
powernow: This module only works with AMD K7 CPUs
bootsplash: status on console 0 changed to on
Older events are logged in the files /var/log/messages and /var/log/warn.
2.2.5 List of Open Files: lsof
To view a list of all the files open for the process with process ID PID, use -p. For
example, to view all the files used by the current shell, enter:
tux@mercury:~> lsof -p $$
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
bash 5552 tux cwd DIR 3,3 1512 117619 /home/tux
bash 5552 tux rtd DIR 3,3 584 2 /
bash 5552 tux txt REG 3,3 498816 13047 /bin/bash
bash 5552 tux mem REG 0,0 0 [heap] (stat: No such
bash 5552 tux mem REG 3,3 217016 115687 /var/run/nscd/passwd
bash 5552 tux mem REG 3,3 208464 11867 /usr/lib/locale/en_GB.
[...]
bash 5552 tux mem REG 3,3 366 9720 /usr/lib/locale/en_GB.
bash 5552 tux mem REG 3,3 97165 8828 /lib/ld-2.3.6.so
bash 5552 tux 0u CHR 136,5 7 /dev/pts/5
bash 5552 tux 1u CHR 136,5 7 /dev/pts/5
bash 5552 tux 2u CHR 136,5 7 /dev/pts/5
bash 5552 tux 255u CHR 136,5 7 /dev/pts/5
The special shell variable $$, whose value is the process ID of the shell, has been
used.
The command lsof lists all the files currently open when used without any parame-
ters. There are often thousands of open files, therefore, listing all of them is rarely