345 lines
11 KiB
Plaintext
345 lines
11 KiB
Plaintext
Documentation for /proc/sys/kernel/* kernel version 2.2.10
|
|
(c) 1998, 1999, Rik van Riel <riel@nl.linux.org>
|
|
|
|
For general info and legal blurb, please look in README.
|
|
|
|
==============================================================
|
|
|
|
This file contains documentation for the sysctl files in
|
|
/proc/sys/kernel/ and is valid for Linux kernel version 2.2.
|
|
|
|
The files in this directory can be used to tune and monitor
|
|
miscellaneous and general things in the operation of the Linux
|
|
kernel. Since some of the files _can_ be used to screw up your
|
|
system, it is advisable to read both documentation and source
|
|
before actually making adjustments.
|
|
|
|
Currently, these files might (depending on your configuration)
|
|
show up in /proc/sys/kernel:
|
|
- acpi_video_flags
|
|
- acct
|
|
- core_pattern
|
|
- core_uses_pid
|
|
- ctrl-alt-del
|
|
- dentry-state
|
|
- domainname
|
|
- hostname
|
|
- hotplug
|
|
- java-appletviewer [ binfmt_java, obsolete ]
|
|
- java-interpreter [ binfmt_java, obsolete ]
|
|
- l2cr [ PPC only ]
|
|
- modprobe ==> Documentation/kmod.txt
|
|
- msgmax
|
|
- msgmnb
|
|
- msgmni
|
|
- osrelease
|
|
- ostype
|
|
- overflowgid
|
|
- overflowuid
|
|
- panic
|
|
- pid_max
|
|
- powersave-nap [ PPC only ]
|
|
- printk
|
|
- real-root-dev ==> Documentation/initrd.txt
|
|
- reboot-cmd [ SPARC only ]
|
|
- rtsig-max
|
|
- rtsig-nr
|
|
- sem
|
|
- sg-big-buff [ generic SCSI device (sg) ]
|
|
- shmall
|
|
- shmmax [ sysv ipc ]
|
|
- shmmni
|
|
- stop-a [ SPARC only ]
|
|
- suid_dumpable
|
|
- sysrq ==> Documentation/sysrq.txt
|
|
- tainted
|
|
- threads-max
|
|
- version
|
|
|
|
==============================================================
|
|
|
|
acpi_video_flags:
|
|
|
|
flags
|
|
|
|
See Doc*/kernel/power/video.txt, it allows mode of video boot to be
|
|
set during run time.
|
|
|
|
==============================================================
|
|
|
|
acct:
|
|
|
|
highwater lowwater frequency
|
|
|
|
If BSD-style process accounting is enabled these values control
|
|
its behaviour. If free space on filesystem where the log lives
|
|
goes below <lowwater>% accounting suspends. If free space gets
|
|
above <highwater>% accounting resumes. <Frequency> determines
|
|
how often do we check the amount of free space (value is in
|
|
seconds). Default:
|
|
4 2 30
|
|
That is, suspend accounting if there left <= 2% free; resume it
|
|
if we got >=4%; consider information about amount of free space
|
|
valid for 30 seconds.
|
|
|
|
==============================================================
|
|
|
|
core_pattern:
|
|
|
|
core_pattern is used to specify a core dumpfile pattern name.
|
|
. max length 64 characters; default value is "core"
|
|
. core_pattern is used as a pattern template for the output filename;
|
|
certain string patterns (beginning with '%') are substituted with
|
|
their actual values.
|
|
. backward compatibility with core_uses_pid:
|
|
If core_pattern does not include "%p" (default does not)
|
|
and core_uses_pid is set, then .PID will be appended to
|
|
the filename.
|
|
. corename format specifiers:
|
|
%<NUL> '%' is dropped
|
|
%% output one '%'
|
|
%p pid
|
|
%u uid
|
|
%g gid
|
|
%s signal number
|
|
%t UNIX time of dump
|
|
%h hostname
|
|
%e executable filename
|
|
%<OTHER> both are dropped
|
|
|
|
==============================================================
|
|
|
|
core_uses_pid:
|
|
|
|
The default coredump filename is "core". By setting
|
|
core_uses_pid to 1, the coredump filename becomes core.PID.
|
|
If core_pattern does not include "%p" (default does not)
|
|
and core_uses_pid is set, then .PID will be appended to
|
|
the filename.
|
|
|
|
==============================================================
|
|
|
|
ctrl-alt-del:
|
|
|
|
When the value in this file is 0, ctrl-alt-del is trapped and
|
|
sent to the init(1) program to handle a graceful restart.
|
|
When, however, the value is > 0, Linux's reaction to a Vulcan
|
|
Nerve Pinch (tm) will be an immediate reboot, without even
|
|
syncing its dirty buffers.
|
|
|
|
Note: when a program (like dosemu) has the keyboard in 'raw'
|
|
mode, the ctrl-alt-del is intercepted by the program before it
|
|
ever reaches the kernel tty layer, and it's up to the program
|
|
to decide what to do with it.
|
|
|
|
==============================================================
|
|
|
|
domainname & hostname:
|
|
|
|
These files can be used to set the NIS/YP domainname and the
|
|
hostname of your box in exactly the same way as the commands
|
|
domainname and hostname, i.e.:
|
|
# echo "darkstar" > /proc/sys/kernel/hostname
|
|
# echo "mydomain" > /proc/sys/kernel/domainname
|
|
has the same effect as
|
|
# hostname "darkstar"
|
|
# domainname "mydomain"
|
|
|
|
Note, however, that the classic darkstar.frop.org has the
|
|
hostname "darkstar" and DNS (Internet Domain Name Server)
|
|
domainname "frop.org", not to be confused with the NIS (Network
|
|
Information Service) or YP (Yellow Pages) domainname. These two
|
|
domain names are in general different. For a detailed discussion
|
|
see the hostname(1) man page.
|
|
|
|
==============================================================
|
|
|
|
hotplug:
|
|
|
|
Path for the hotplug policy agent.
|
|
Default value is "/sbin/hotplug".
|
|
|
|
==============================================================
|
|
|
|
l2cr: (PPC only)
|
|
|
|
This flag controls the L2 cache of G3 processor boards. If
|
|
0, the cache is disabled. Enabled if nonzero.
|
|
|
|
==============================================================
|
|
|
|
osrelease, ostype & version:
|
|
|
|
# cat osrelease
|
|
2.1.88
|
|
# cat ostype
|
|
Linux
|
|
# cat version
|
|
#5 Wed Feb 25 21:49:24 MET 1998
|
|
|
|
The files osrelease and ostype should be clear enough. Version
|
|
needs a little more clarification however. The '#5' means that
|
|
this is the fifth kernel built from this source base and the
|
|
date behind it indicates the time the kernel was built.
|
|
The only way to tune these values is to rebuild the kernel :-)
|
|
|
|
==============================================================
|
|
|
|
overflowgid & overflowuid:
|
|
|
|
if your architecture did not always support 32-bit UIDs (i.e. arm, i386,
|
|
m68k, sh, and sparc32), a fixed UID and GID will be returned to
|
|
applications that use the old 16-bit UID/GID system calls, if the actual
|
|
UID or GID would exceed 65535.
|
|
|
|
These sysctls allow you to change the value of the fixed UID and GID.
|
|
The default is 65534.
|
|
|
|
==============================================================
|
|
|
|
panic:
|
|
|
|
The value in this file represents the number of seconds the
|
|
kernel waits before rebooting on a panic. When you use the
|
|
software watchdog, the recommended setting is 60.
|
|
|
|
==============================================================
|
|
|
|
panic_on_oops:
|
|
|
|
Controls the kernel's behaviour when an oops or BUG is encountered.
|
|
|
|
0: try to continue operation
|
|
|
|
1: delay a few seconds (to give klogd time to record the oops output) and
|
|
then panic. If the `panic' sysctl is also non-zero then the machine will
|
|
be rebooted.
|
|
|
|
==============================================================
|
|
|
|
pid_max:
|
|
|
|
PID allocation wrap value. When the kenrel's next PID value
|
|
reaches this value, it wraps back to a minimum PID value.
|
|
PIDs of value pid_max or larger are not allocated.
|
|
|
|
==============================================================
|
|
|
|
powersave-nap: (PPC only)
|
|
|
|
If set, Linux-PPC will use the 'nap' mode of powersaving,
|
|
otherwise the 'doze' mode will be used.
|
|
|
|
==============================================================
|
|
|
|
printk:
|
|
|
|
The four values in printk denote: console_loglevel,
|
|
default_message_loglevel, minimum_console_loglevel and
|
|
default_console_loglevel respectively.
|
|
|
|
These values influence printk() behavior when printing or
|
|
logging error messages. See 'man 2 syslog' for more info on
|
|
the different loglevels.
|
|
|
|
- console_loglevel: messages with a higher priority than
|
|
this will be printed to the console
|
|
- default_message_level: messages without an explicit priority
|
|
will be printed with this priority
|
|
- minimum_console_loglevel: minimum (highest) value to which
|
|
console_loglevel can be set
|
|
- default_console_loglevel: default value for console_loglevel
|
|
|
|
==============================================================
|
|
|
|
printk_ratelimit:
|
|
|
|
Some warning messages are rate limited. printk_ratelimit specifies
|
|
the minimum length of time between these messages (in jiffies), by
|
|
default we allow one every 5 seconds.
|
|
|
|
A value of 0 will disable rate limiting.
|
|
|
|
==============================================================
|
|
|
|
printk_ratelimit_burst:
|
|
|
|
While long term we enforce one message per printk_ratelimit
|
|
seconds, we do allow a burst of messages to pass through.
|
|
printk_ratelimit_burst specifies the number of messages we can
|
|
send before ratelimiting kicks in.
|
|
|
|
==============================================================
|
|
|
|
reboot-cmd: (Sparc only)
|
|
|
|
??? This seems to be a way to give an argument to the Sparc
|
|
ROM/Flash boot loader. Maybe to tell it what to do after
|
|
rebooting. ???
|
|
|
|
==============================================================
|
|
|
|
rtsig-max & rtsig-nr:
|
|
|
|
The file rtsig-max can be used to tune the maximum number
|
|
of POSIX realtime (queued) signals that can be outstanding
|
|
in the system.
|
|
|
|
rtsig-nr shows the number of RT signals currently queued.
|
|
|
|
==============================================================
|
|
|
|
sg-big-buff:
|
|
|
|
This file shows the size of the generic SCSI (sg) buffer.
|
|
You can't tune it just yet, but you could change it on
|
|
compile time by editing include/scsi/sg.h and changing
|
|
the value of SG_BIG_BUFF.
|
|
|
|
There shouldn't be any reason to change this value. If
|
|
you can come up with one, you probably know what you
|
|
are doing anyway :)
|
|
|
|
==============================================================
|
|
|
|
shmmax:
|
|
|
|
This value can be used to query and set the run time limit
|
|
on the maximum shared memory segment size that can be created.
|
|
Shared memory segments up to 1Gb are now supported in the
|
|
kernel. This value defaults to SHMMAX.
|
|
|
|
==============================================================
|
|
|
|
suid_dumpable:
|
|
|
|
This value can be used to query and set the core dump mode for setuid
|
|
or otherwise protected/tainted binaries. The modes are
|
|
|
|
0 - (default) - traditional behaviour. Any process which has changed
|
|
privilege levels or is execute only will not be dumped
|
|
1 - (debug) - all processes dump core when possible. The core dump is
|
|
owned by the current user and no security is applied. This is
|
|
intended for system debugging situations only. Ptrace is unchecked.
|
|
2 - (suidsafe) - any binary which normally would not be dumped is dumped
|
|
readable by root only. This allows the end user to remove
|
|
such a dump but not access it directly. For security reasons
|
|
core dumps in this mode will not overwrite one another or
|
|
other files. This mode is appropriate when adminstrators are
|
|
attempting to debug problems in a normal environment.
|
|
|
|
==============================================================
|
|
|
|
tainted:
|
|
|
|
Non-zero if the kernel has been tainted. Numeric values, which
|
|
can be ORed together:
|
|
|
|
1 - A module with a non-GPL license has been loaded, this
|
|
includes modules with no license.
|
|
Set by modutils >= 2.4.9 and module-init-tools.
|
|
2 - A module was force loaded by insmod -f.
|
|
Set by modutils >= 2.4.9 and module-init-tools.
|
|
4 - Unsafe SMP processors: SMP with CPUs not designed for SMP.
|
|
|