Linux notebook / System

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System

File system rules

syslog

Some file system rules for Linux

/usr should hold only shareable, read-only data (should be able to be mounted R/O)

/var/run and /tmp should be cleared when the system boots

/root permissions should be 0700

/tmp permissions should be 1777

/sbin permissions should be 0700

/lib must reside in the same partition as /

syslog configuration

The syslog system is configured trough the file /etc/syslog.conf.

This file is made of lines, each with two fields: selector and action, separated by TABs (according to the manual, spaces can be used, but rumour has it the syslogd daemon is broken in this).

The selector field is made of two dot separated parts: facility and priority.

The facility defines the class of the message, and can be...

auth

authpriv

cron

daemon

kern

lpr

mail

mark (internal use only)

news

security (same as auth, deprecated)

syslog

user

uucp

local0 trough local7

* (wildcard)

The priority defines the severity of the message, and can be...

debug

info

notice

warning

warn (deprecated)

err

error (deprecated)

crit

alert

emerg

panic (deprecated)

* (wildcard)

none (no priority for the given facility)

Multiple comma separated facilities can be used in the same selector.

Module configuration

Notes:

Empty lines are ignored

Continuation lines are supported, a \ at the end of the line is ignored and makes the following line continue the present

The lines are processed trough the shell, so wild-cards, back-ticks, etc, can be used

The pre and post commands aren't executed when the module is loaded or unloaded by kerneld

Command Meaning Examples

#.... Comment, ignored

keep Don't drop system path list

depfile=DEPFILE_PATH Path to the system module dependency file, used by modprobe to load modules depending from others. Usually created by depmod depfile=/lib/modules/`uname -r`/modules.dep

path=SOME_PATH Defines a path where modules are to be searched path=/lib/modules

path[tag]=SOME_PATH Defines a path where modules are to be searched, under conditions associated with the tag path[fs]=/lib/modules/`uname -r`

options module symbol=value ... Define options for the given module modprobe de620 bnc=1

alias fake_name real_name Creates an alias for a module name alias iso9660 isofs # now you can modprobe iso9660

alias module off Prevents loading of a given module alias net-pf-4 off # prevents loading of IPX

pre-install module command ... Command is executed before the module is installed

install module command ... Command is executed when the module is installed

post-install module command ... Command is executed after the module is installed

pre-remove module command ... Command is executed before the module is removed

remove module command ... Command is executed when the module is removed

post-remove module command ... Command is executed after the module is removed

Command	Meaning	Examples
`#....`	Comment, ignored
`keep`	Don't drop system path list
`depfile=DEPFILE_PATH`	Path to the system module dependency file, used by modprobe to load modules depending from others. Usually created by depmod	depfile=/lib/modules/`uname -r`/modules.dep
`path=SOME_PATH`	Defines a path where modules are to be searched	`path=/lib/modules`
`path[tag]=SOME_PATH`	Defines a path where modules are to be searched, under conditions associated with the tag	path[fs]=/lib/modules/`uname -r`
`options module symbol=value ...`	Define options for the given module	`modprobe de620 bnc=1`
`alias fake_name real_name`	Creates an alias for a module name	`alias iso9660 isofs # now you can modprobe iso9660`
`alias module off`	Prevents loading of a given module	`alias net-pf-4 off # prevents loading of IPX`
`pre-install module command ...`	Command is executed before the module is installed
`install module command ...`	Command is executed when the module is installed
`post-install module command ...`	Command is executed after the module is installed
`pre-remove module command ...`	Command is executed before the module is removed
`remove module command ...`	Command is executed when the module is removed
`post-remove module command ...`	Command is executed after the module is removed

Kernel configuration for CD-Writers

Notes:

Y means the feature must be compiled in the kernel

M means the feature must be compiled as a module

Y/M means the feature can be compiled in the kernel or as a module

Section Description Module For SCSI writer For IDE writer For parallel port writer

BLOCK Enhanced IDE/MFM/RLL... Y

IDE/ATAPI CDROM ide-cd M

SCSI hostadaptor emulation ide-scsi M

Loopback device loop M M M

PARIDE Parallel port IDE device paride Y/M

Parallel port ATAPI CD-ROMs M

Parallel port generic ATAPI M

(select a low-level driver) Y

SCSI SCSI support scsi_mod Y/M Y/M

SCSI CD-ROM support sr_mod Y/M Y/M

Enable vendor-specific Y Y

SCSI generic support sg Y/M Y/M

(select a low-level driver) Y

FS ISO 9660 CDROM filesystem iso9660 Y Y Y

Microsoft Joliet cdrom... joliet M/Y M/Y M/Y

Section	Description	Module	For SCSI writer	For IDE writer	For parallel port writer
BLOCK	Enhanced IDE/MFM/RLL...			Y
IDE/ATAPI CDROM	ide-cd		M
SCSI hostadaptor emulation	ide-scsi		M
Loopback device	loop	M	M	M
PARIDE	Parallel port IDE device	paride			Y/M
Parallel port ATAPI CD-ROMs				M
Parallel port generic ATAPI				M
(select a low-level driver)				Y
SCSI	SCSI support	scsi_mod	Y/M	Y/M
SCSI CD-ROM support	sr_mod	Y/M	Y/M
Enable vendor-specific		Y	`Y`
SCSI generic support	sg	Y/M	Y/M
(select a low-level driver)		Y
FS	ISO 9660 CDROM filesystem	iso9660	Y	Y	Y
Microsoft Joliet cdrom...	joliet	M/Y	M/Y	M/Y

Available signals

Available signals

Signal Value
(- is signal absent) Action Conformance Comment

SIGHUP 1 A POSIX.1 Hangup detected on controlling terminal or death of controlling process

SIGINT 2 A POSIX.1 Interrupt from keyboard

SIGQUIT 3 A POSIX.1 Quit from keyboard

SIGILL 4 A POSIX.1 Illegal Instruction

SIGABRT 6 C POSIX.1 Abort signal from abort(3)

SIGFPE 8 C POSIX.1 Floating point exception

SIGKILL 9 AEF POSIX.1 Kill signal

SIGSEGV 11 C POSIX.1 Invalid memory reference

SIGPIPE 13 A POSIX.1 Broken pipe: write to pipe with no readers

SIGALRM 14 A POSIX.1 Timer signal from alarm(2)

SIGTERM 15 A POSIX.1 Termination signal

SIGUSR1 10 A POSIX.1 User-defined signal 1

SIGUSR2 12 A POSIX.1 User-defined signal 2

SIGCHLD 17 B POSIX.1 Child stopped or terminated

SIGCONT 18 POSIX.1 Continue if stopped

SIGSTOP 19 DEF POSIX.1 Stop process

SIGTSTP 20 D POSIX.1 Stop typed at tty

SIGTTIN 21 D POSIX.1 tty input for background process

SIGTTOU 22 D POSIX.1 tty output for background process

SIGTRAP 5 CG Trace/breakpoint trap

SIGIOT 6 CG IOT trap. A synonym for SIGABRT

SIGEMT - G

SIGBUS 7 AG Bus error

SIGSYS - G Bad argument to routine (SVID)

SIGSTKFLT 16 AG Stack fault on coprocessor

SIGURG 23 BG Urgent condition on socket (4.2 BSD)

SIGIO 29 AG I/O now possible (4.2 BSD)

SIGPOLL 29 AG A synonym for SIGIO (System V)

SIGCLD - G A synonym for SIGCHLD

SIGXCPU 24 AG CPU time limit exceeded (4.2 BSD)

SIGXFSZ 25 AG File size limit exceeded (4.2 BSD)

SIGVTALRM 26 AG Virtual alarm clock (4.2 BSD)

SIGPROF 27 AG Profile alarm clock

SIGPWR 30 AG Power failure (System V)

SIGINFO - G A synonym for SIGPWR

SIGLOST - AG File lock lost

SIGWINCH 28 BG Window resize signal (4.3 BSD, Sun)

SIGUNUSED 31 AG Unused signal

Key to action column

A Default action is to terminate the process

B Default action is to ignore the signal

C Default action is to dump core

D Default action is to stop the process

E Signal cannot be caught

F Signal cannot be ignored

G Not a POSIX.1 conformant signal

Available signals
Signal	Value (- is signal absent)	Action	Conformance	Comment
SIGHUP	1	A	POSIX.1	Hangup detected on controlling terminal or death of controlling process
SIGINT	2	A	POSIX.1	Interrupt from keyboard
SIGQUIT	3	A	POSIX.1	Quit from keyboard
SIGILL	4	A	POSIX.1	Illegal Instruction
SIGABRT	6	C	POSIX.1	Abort signal from abort(3)
SIGFPE	8	C	POSIX.1	Floating point exception
SIGKILL	9	AEF	POSIX.1	Kill signal
SIGSEGV	11	C	POSIX.1	Invalid memory reference
SIGPIPE	13	A	POSIX.1	Broken pipe: write to pipe with no readers
SIGALRM	14	A	POSIX.1	Timer signal from alarm(2)
SIGTERM	15	A	POSIX.1	Termination signal
SIGUSR1	10	A	POSIX.1	User-defined signal 1
SIGUSR2	12	A	POSIX.1	User-defined signal 2
SIGCHLD	17	B	POSIX.1	Child stopped or terminated
SIGCONT	18		POSIX.1	Continue if stopped
SIGSTOP	19	DEF	POSIX.1	Stop process
SIGTSTP	20	D	POSIX.1	Stop typed at tty
SIGTTIN	21	D	POSIX.1	tty input for background process
SIGTTOU	22	D	POSIX.1	tty output for background process
SIGTRAP	5	CG		Trace/breakpoint trap
SIGIOT	6	CG		IOT trap. A synonym for SIGABRT
SIGEMT	-	G
SIGBUS	7	AG		Bus error
SIGSYS	-	G		Bad argument to routine (SVID)
SIGSTKFLT	16	AG		Stack fault on coprocessor
SIGURG	23	BG		Urgent condition on socket (4.2 BSD)
SIGIO	29	AG		I/O now possible (4.2 BSD)
SIGPOLL	29	AG		A synonym for SIGIO (System V)
SIGCLD	-	G		A synonym for SIGCHLD
SIGXCPU	24	AG		CPU time limit exceeded (4.2 BSD)
SIGXFSZ	25	AG		File size limit exceeded (4.2 BSD)
SIGVTALRM	26	AG		Virtual alarm clock (4.2 BSD)
SIGPROF	27	AG		Profile alarm clock
SIGPWR	30	AG		Power failure (System V)
SIGINFO	-	G		A synonym for SIGPWR
SIGLOST	-	AG		File lock lost
SIGWINCH	28	BG		Window resize signal (4.3 BSD, Sun)
SIGUNUSED	31	AG		Unused signal
Key to action column
A	Default action is to terminate the process
B	Default action is to ignore the signal
C	Default action is to dump core
D	Default action is to stop the process
E	Signal cannot be caught
F	Signal cannot be ignored
G	Not a POSIX.1 conformant signal

How to disable ping'ing of a host (Kernel 2.1.xx or newer)

To ignore pings

echo 1 > /proc/sys/net/ipv4/icmp_echo_ignore_all

To acknowledge pings

echo 0 > /proc/sys/net/ipv4/icmp_echo_ignore_all

How to set 32 bit mode for (E)IDE drives

To set 32 bit mode

hdparm -c3 /dev/hdX

To set 16 bit mode

hdparm -c0 /dev/hdX

To test

hdparm -t /dev/hdX

crontab format (for Dillon's daemon)

crontab file format

minutes hour day_of_month month day_of_week command

minutes A value; a range (0-59), optionally followed by a slash and a skip factor ; * ; or comma separated values or ranges

*

every minute

10

at 10 minutes in the hour

*/15

every 15 minutes

0,20,40

at 0, 20 and 40 minutes in the hour

0-10/2

every 2 minutes during the first 10 minutes in the hour

hour A value; a range (0-23), optionally followed by a slash and a skip factor ; * ; or comma separated values or ranges similar to minutes, above

day_of_month A value; a range (0-31), optionally followed by a slash and a skip factor ; * ; or comma separated values or ranges. When used with day_of_week, the matches are ORed similar to minutes, above

month A month name (jan,feb,mar,etc);a range (jan-dec); or comma separated values or ranges

apr

During April

jul-sep

From July to September

mar,oct

In March and October

day_of_week A day name (mon,tue,wed,etc);a range (sun-sat); or comma separated values or ranges similar to months above

command Executed with /bin/sh -c; frequently starts with exec, therefore causing the command to replace the shell

crontab file format
minutes hour day_of_month month day_of_week command
minutes	A value; a range (0-59), optionally followed by a slash and a skip factor ; * ; or comma separated values or ranges	* every minute 10 at 10 minutes in the hour */15 every 15 minutes 0,20,40 at 0, 20 and 40 minutes in the hour 0-10/2 every 2 minutes during the first 10 minutes in the hour
hour	A value; a range (0-23), optionally followed by a slash and a skip factor ; * ; or comma separated values or ranges	similar to minutes, above
day_of_month	A value; a range (0-31), optionally followed by a slash and a skip factor ; * ; or comma separated values or ranges. When used with day_of_week, the matches are ORed	similar to minutes, above
month	A month name (jan,feb,mar,etc);a range (jan-dec); or comma separated values or ranges	apr During April jul-sep From July to September mar,oct In March and October
day_of_week	A day name (mon,tue,wed,etc);a range (sun-sat); or comma separated values or ranges	similar to months above
command	Executed with /bin/sh -c; frequently starts with exec, therefore causing the command to replace the shell

Last update: Wed, 2 Nov 2005 10:16:21 GMT

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