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System |
File system rules | syslog | conf.modules | CD-Writers | signals | pings | Optimization | cron
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> 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

> 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

> 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

> 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

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