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- Lines: 1354
- Date:
Wed Dec 31 16:00:00 1969
- Orig file:
v2.3.18/linux/Documentation/proc.txt
- Orig date:
Sat Feb 6 12:46:20 1999
diff -u --recursive --new-file v2.3.18/linux/Documentation/proc.txt linux/Documentation/proc.txt
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-
------------------------------------------------------------------------
-
- T H E /proc F I L E S Y S T E M
-
------------------------------------------------------------------------
-/proc/sys Terrehon Bowden <terrehon@wpi.com> January 27 1999
- Bodo Bauer <bb@ricochet.net>
------------------------------------------------------------------------
-Version 1.1 Kernel version 2.2
------------------------------------------------------------------------
-Contents
-
-1 Introduction/Credits
-
-1.1 Legal Issues
-
-2 The /proc file system
-
-2.1 Process specific subdirectories
-2.2 Kernel data
-2.3 IDE devices in /proc/ide
-2.4 Networking info in /proc/net
-2.5 SCSI info
-2.6 Parallel port info in /proc/parport
-2.7 TTY info in /proc/tty
-
-3 Reading and modifying kernel parameters
-
-3.1 /proc/sys/debug and /proc/sys/proc
-3.2 /proc/fs - File system data
-3.3 /proc/fs/binfmt_misc - Miscellaneous binary formats
-3.4 /proc/sys/kernel - General kernel parameters
-3.5 /proc/sys/vm - The virtual memory subsystem
-3.6 /proc/sys/dev - Device specific parameters
-3.7 /proc/sys/sunrpc - Remote procedure calls
-3.8 /proc/sys/net - Networking stuff
-3.9 /proc/sys/net/ipv4 - IPV4 settings=20
-3.10 Appletalk
-3.11 IPX
-
------------------------------------------------------------------------
-
-1 Introduction/Credits
-
-This documentation is part of a soon to be released book published by
-IDG Books on the SuSE Linux distribution. As there is no complete
-documentation for the /proc file system and we've used many freely
-available sources to write this chapter, it seems only fair to give
-the work back to the Linux community. This work is based on the
-2.1.132 and 2.2.0-pre-kernel versions. I'm afraid it's still far from
-complete, but we hope it will be useful. As far as we know, it is the
-first 'all-in-one' document about the /proc file system. It is
-focused on the Intel x86 hardware, so if you are looking for PPC, ARM,
-SPARC, APX, etc., features, you probably won't find what you are
-looking for. It also only covers IPv4 networking, not IPv6 nor other
-protocols - sorry.
-
-We'd like to thank Alan Cox, Rik van Riel, and Alexey Kuznetsov. We'd
-also like to extend a special thank you to Andi Kleen for
-documentation, which we relied on heavily to create this document, as
-well as the additional information he provided. Thanks to everybody
-else who contributed source or docs to the Linux kernel and helped
-create a great piece of software... :)
-
-If you have any comments, corrections or additions, please don't
-hesitate to contact Bodo Bauer at bb@ricochet.net. We'll be happy to
-add them to this document.
-
-The latest version of this document is available online at
-http://www.suse.com/~bb/Docs/proc.html in HTML, ASCII, and as
-Postscript file.
-
-1.1 Legal Stuff
-
-We don't guarantee the correctness of this document, and if you come
-to us complaining about how you screwed up your system because of
-incorrect documentation, we won't feel responsible...
-
------------------------------------------------------------------------
-
-2 The /proc file system
-
-The proc file system acts as an interface to internal data structures
-in the kernel. It can be used to obtain information about the system
-and to change certain kernel parameters at runtime. It contains
-(among other things) one subdirectory for each process running on the
-system which is named after the process id (PID) of the process. The
-link self points to the process reading the file system.
-
-2.1 Process specific subdirectories
-
-Each process subdirectory has the in table 1.1 listed entries.
-
- _________________________________________________
- cmdline Command line arguments
- environ Values of environment variables
- fd Directory, which contains all file descriptors
- mem Memory held by this process
- stat Process status
- status Process status in human readable form
- cwd Link to the current working directory
- exe Link to the executable of this process
- maps Memory maps
- root Link to the root directory of this process
- statm Process memory status information
- _________________________________________________
- Table 1.1: Process specific entries in /proc
-
-For example, to get the status information of a process, all you have
-to do is read the file /proc/PID/status:
-
-> cat /proc/self/status
-Name: cat
-State: R (running)
-Pid: 5633
-PPid: 5609
-Uid: 501 501 501 501
-Gid: 100 100 100 100
-Groups: 100 16
-VmSize: 804 kB
-VmLck: 0 kB
-VmRSS: 344 kB
-VmData: 68 kB
-VmStk: 20 kB
-VmExe: 12 kB
-VmLib: 660 kB
-SigPnd: 0000000000000000
-SigBlk: 0000000000000000
-SigIgn: 0000000000000000
-SigCgt: 0000000000000000
-CapInh: 00000000fffffeff
-CapPrm: 0000000000000000
-CapEff: 0000000000000000
-
-This shows you almost the same information as you would get if you
-viewed it with the ps command. In fact, ps uses the proc file system
-to obtain its information.
-
-The statm file contains more detailed information about the process
-memory usage. It contains seven values with the following meanings:
-
-size total program size
-resident size of in memory portions
-shared number of the pages that are shared
-trs number of pages that are 'code'
-drs number of pages of data/stack
-lrs number of pages of library
-dt number of dirty pages
-
-The ratio text/data/library is approximate only by heuristics.
-
-2.2 Kernel data
-
-Similar to the process entries, these are files which give information
-about the running kernel. The files used to obtain this information
-are contained in /proc and are listed in table 1.2. Not all of these
-will be present in your system. It depends on the kernel configuration
-and the loaded modules, which files are there, and which are missing.
-
- ________________________________________________
- apm Advanced power management info
- cmdline Kernel command line
- cpuinfo Info about the CPU
- devices Available devices (block and character)
- dma Used DMS channels
- filesystems Supported filesystems
- interrupts Interrupt usage
- ioports I/O port usage
- kcore Kernel core image
- kmsg Kernel messages
- ksyms Kernel symbol table
- loadavg Load average
- locks Kernel locks
- meminfo Memory info
- misc Miscellaneous
- modules List of loaded modules
- mounts Mounted filesystems
- partitions Table of partitions known to the system
- rtc Real time clock
- slabinfo Slab pool info
- stat Overall statistics
- swaps Swap space utilization
- uptime System uptime
- version Kernel version
- ________________________________________________
- Table 1.2: Kernel info in /proc
-
-You can, for example, check which interrupts are currently in use and
-what they are used for by looking in the file /proc/interrupts:
-
-> cat /proc/interrupts
- CPU0
- 0: 8728810 XT-PIC timer
- 1: 895 XT-PIC keyboard
- 2: 0 XT-PIC cascade
- 3: 531695 XT-PIC aha152x
- 4: 2014133 XT-PIC serial
- 5: 44401 XT-PIC pcnet_cs
- 8: 2 XT-PIC rtc
- 11: 8 XT-PIC i82365
- 12: 182918 XT-PIC PS/2 Mouse
- 13: 1 XT-PIC fpu
- 14: 1232265 XT-PIC ide0
- 15: 7 XT-PIC ide1
-NMI: 0
-
-There three more important subdirectories in /proc: net, scsi and
-sys. The general rule is that the contents, or even the existence of
-these directories, depends on your kernel configuration. If SCSI is
-not enabled, the directory scsi may not exist. The same is true with
-the net, which is only there when networking support is present in the
-running kernel.
-
-The slabinfo file gives information about memory usage on the slab
-level. Linux uses slab pools for memory management above page level
-in version 2.2. Commonly used objects have their own slab pool (like
-network buffers, directory cache, etc.).
-
-2.3 IDE devices in /proc/ide
-
-This subdirectory contains information about all IDE devices that the
-kernel is aware of. There is one subdirectory for each device
-(i.e. hard disk) containing the following files:
-
- cache The cache
- capacity Capacity of the medium
- driver Driver and version
- geometry Physical and logical geometry
- identify Device identify block
- media Media type
- model Device identifier
- settings Device setup
- smart_thresholds IDE disk management thresholds
- smart_values IDE disk management values
-
-2.4 Networking info in /proc/net
-
-This directory follows the usual pattern. Table 1.3 lists the files
-and their meaning.
-
- ____________________________________________________
- arp Kernel ARP table
- dev network devices with statistics
- dev_mcast Lists the Layer2 multicast groups a
- device is listening to (interface index,
- label, number of references, number of
- bound addresses).
- dev_stat network device status
- ip_fwchains Firewall chain linkage
- ip_fwnames Firewall chains
- ip_masq Directory containing the masquerading
- tables.
- ip_masquerade Major masquerading table
- netstat Network statistics
- raw Raw device statistics
- route Kernel routing table
- rpc Directory containing rpc info
- rt_cache Routing cache
- snmp SNMP data
- sockstat Socket statistics
- tcp TCP sockets
- tr_rif Token ring RIF routing table
- udp UDP sockets
- unix UNIX domain sockets
- wireless Wireless interface data (Wavelan etc)
- igmp IP multicast addresses, which this host joined
- psched Global packet scheduler parameters.
- netlink List of PF_NETLINK sockets.
- ip_mr_vifs List of multicast virtual interfaces.
- ip_mr_cache List of multicast routing cache.
- udp6 UDP sockets (IPv6)
- tcp6 TCP sockets (IPv6)
- raw6 Raw device statistics (IPv6)
- igmp6 IP multicast addresses, which this host joineed (IPv6)
- if_inet6 List of IPv6 interface addresses.
- ipv6_route Kernel routing table for IPv6
- rt6_stats global IPv6 routing tables statistics.
- sockstat6 Socket statistics (IPv6)
- snmp6 Snmp data (IPv6)
- ____________________________________________________
- Table 1.3: Network info in /proc/net
-
-You can use this information to see which network devices are
-available in your system and how much traffic was routed over those
-devices:
-
-> cat /proc/net/dev
-Inter-|Receive |[...
- face |bytes packets errs drop fifo frame compressed multicast|[...
- lo: 908188 5596 0 0 0 0 0 0 [...
- ppp0:15475140 20721 410 0 0 410 0 0 [...
- eth0: 614530 7085 0 0 0 0 0 1 [...
-
-...] Transmit
-...] bytes packets errs drop fifo colls carrier compressed
-...] 908188 5596 0 0 0 0 0 0
-...] 1375103 17405 0 0 0 0 0 0
-...] 1703981 5535 0 0 0 3 0 0
-
-2.5 SCSI info
-
-If you have a SCSI host adapter in your system, you'll find a
-subdirectory named after the driver for this adapter in /proc/scsi.
-You'll also see a list of all recognized SCSI devices in /proc/scsi:
-
->cat /proc/scsi/scsi
-Attached devices:
-Host: scsi0 Channel: 00 Id: 00 Lun: 00
- Vendor: QUANTUM Model: XP34550W Rev: LXY4
- Type: Direct-Access ANSI SCSI revision: 02
-Host: scsi0 Channel: 00 Id: 01 Lun: 00
- Vendor: SEAGATE Model: ST34501W Rev: 0018
- Type: Direct-Access ANSI SCSI revision: 02
-Host: scsi0 Channel: 00 Id: 02 Lun: 00
- Vendor: SEAGATE Model: ST34501W Rev: 0017
- Type: Direct-Access ANSI SCSI revision: 02
-Host: scsi0 Channel: 00 Id: 04 Lun: 00
- Vendor: ARCHIVE Model: Python 04106-XXX Rev: 703b
- Type: Sequential-Access ANSI SCSI revision: 02
-
-The directory named after the driver has one file for each adapter
-found in the system. These files contain information about
-the controller, including the used IRQ and the IO address range:
-
->cat /proc/scsi/ncr53c8xx/0
-General information:
- Chip NCR53C875, device id 0xf, revision id 0x4
- IO port address 0xec00, IRQ number 11
- Synchronous period factor 12, max commands per lun 4
-
-2.6 Parallel port info in /proc/parport
-
-The directory /proc/parport contains information about the parallel
-ports of your system. It has one subdirectory for each port, named
-after the port number (0,1,2,...).
-
-This directory contains four files:
-
- autoprobe Autoprobe results of this port
- devices Connected device modules
- hardware Hardware info (port type, io-port, DMA, IRQ, etc.)
- irq Used interrupt, if any
-
-2.7 TTY info in /proc/tty
-
-Information about the available and the actually used tty's can be
-found in /proc/tty. You'll find entries for drivers and line
-disciplines in this directory, as shown in the table below:
-
- drivers List of drivers and their usage
- ldiscs Registered line disciplines
- driver/serial Usage statistic and status of single tty lines
-
-To see which tty's are currently in use, you can simply look into the
-file /proc/tty/drivers:
-
->cat /proc/tty/drivers
-pty_slave /dev/pts 136 0-255 pty:slave
-pty_master /dev/ptm 128 0-255 pty:master
-pty_slave /dev/ttyp 3 0-255 pty:slave
-pty_master /dev/pty 2 0-255 pty:master
-serial /dev/cua 5 64-67 serial:callout
-serial /dev/ttyS 4 64-67 serial
-/dev/tty0 /dev/tty0 4 0 system:vtmaster
-/dev/ptmx /dev/ptmx 5 2 system
-/dev/console /dev/console 5 1 system:console
-/dev/tty /dev/tty 5 0 system:/dev/tty
-unknown /dev/tty 4 1-63 console
-
------------------------------------------------------------------------
-
-3 Reading and modifying kernel parameters
-
-A very interesting part of /proc is the directory /proc/sys. This not
-only provides information, it also allows you to change parameters
-within the kernel. Be very careful when trying this. You can optimize
-your system, but you also can crash it. Never play around with kernel
-parameters on a production system. Set up a development machine and
-test to make sure that everything works the way you want it to. You
-may have no alternative but to reboot the machine once an error has
-been made.
-
-To change a value, simply echo the new value into the file. An example
-is given below in the section on the file system data. You need to be
-root to do this. You can create your own boot script to get this done
-every time your system boots.
-
-The files in /proc/sys can be used to tune and monitor miscellaneous
-and general things in the operation of the Linux kernel. Since some
-of the files can inadvertently disrupt your system, it is advisable to
-read both documentation and source before actually making
-adjustments. In any case, be very careful when writing to any of these
-files. The entries in /proc may change slightly between the 2.1.* and
-the 2.2 kernel, so review the kernel documentation if there is any
-doubt. You'll find the documentation in the directory
-/usr/src/linux/Documentation/sys. This chapter is heavily based on the
-documentation included in the pre 2.2 kernels. Thanks to Rick van Riel
-for providing this information.
-
-3.1 /proc/sys/debug and /proc/sys/proc
-
-These two subdirectories are empty.
-
-3.2 /proc/fs - File system data
-
-This subdirectory contains specific file system, file handle, inode,
-dentry and quota information.
-
-Currently, these files are in /proc/sys/fs:
-
-dentry-state
- Status of the directory cache. Since directory entries are
- dynamically allocated and deallocated, this file gives information
- about the current status. It holds six values, in which the last
- two are not used and are always zero. The other four mean:
-
- nr_dentry Seems to be zero all the time
- nr_unused Number of unused cache entries
- age_limit Age in seconds after the entry may be
- reclaimed, when memory is short
- want_pages internal
-
-dquot-nr and dquot-max
- The file dquot-max shows the maximum number of cached disk quota
- entries.
-
- The file dquot-nr shows the number of allocated disk quota
- entries and the number of free disk quota entries.
-
- If the number of free cached disk quotas is very low and you have
- a large number of simultaneous system users, you might want
- to raise the limit.
-
-file-nr and file-max
- The kernel allocates file handles dynamically, but as yet
- doesn't free them again.
-
- The value in file-max denotes the maximum number of file handles
- that the Linux kernel will allocate. When you get a lot of error
- messages about running out of file handles, you might want to raise
- this limit. The default value is 4096. To change it, just write the
- new number into the file:
-
- # cat /proc/sys/fs/file-max
- 4096
- # echo 8192 > /proc/sys/fs/file-max
- # cat /proc/sys/fs/file-max
- 8192
-
- This method of revision is useful for all customizable parameters
- of the kernel - simply echo the new value to the corresponding
- file.
-
- The three values in file-nr denote the number of allocated file
- handles, the number of used file handles, and the maximum number of
- file handles. When the allocated file handles come close to the
- maximum, but the number of actually used ones is far behind, you've
- encountered a peak in your usage of file handles and you don't need
- to increase the maximum.
-
- However, there is still a per process limit of open files, which
- unfortunatly can't be changed that easily. It is set to 1024 by
- default. To change this you have to edit the files limits.h and
- fs.h in the directory /usr/src/linux/include/linux. Change the
- definition of NR_OPEN and recompile the kernel.
-
-inode-state, inode-nr and inode-max
- As with file handles, the kernel allocates the inode structures
- dynamically, but can't free them yet.
-
- The value in inode-max denotes the maximum number of inode
- handlers. This value should be 3 to 4 times larger than the value
- in file-max, since stdin, stdout, and network sockets also need an
- inode struct to handle them. If you regularly run out of inodes,
- you should increase this value.
-
- The file inode-nr contains the first two items from inode-state, so
- we'll skip to that file...
-
- inode-state contains three actual numbers and four dummy values. The
- actual numbers are (in order of appearance) nr_inodes, nr_free_inodes,
- and preshrink.
-
- nr_inodes
- Denotes the number of inodes the system has allocated. This can
- be slightly more than inode-max because Linux allocates them one
- pageful at a time.
-
- nr_free_inodes
- Represents the number of free inodes and pre shrink is nonzero
- when the nr_inodes > inode-max and the system needs to prune the
- inode list instead of allocating more.
-
-super-nr and super-max
- Again, super block structures are allocated by the kernel,
- but not freed. The file super-max contains the maximum number of
- super block handlers, where super-nr shows the number of
- currently allocated ones.
-
- Every mounted file system needs a super block, so if you plan to
- mount lots of file systems, you may want to increase these
- numbers.
-
-3.3 /proc/fs/binfmt_misc - Miscellaneous binary formats
-
-Besides these files, there is the subdirectory
-/proc/sys/fs/binfmt_misc. This handles the kernel support for
-miscellaneous binary formats.
-
-Binfmt_misc provides the ability to register additional binary formats
-to the Kernel without compiling an additional module/kernel. Therefore
-binfmt_misc needs to know magic numbers at the beginning or the
-filename extension of the binary.
-
-It works by maintaining a linked list of structs, that contain a
-description of a binary format, including a magic with size (or the
-filename extension), offset and mask, and the interpreter name. On
-request it invokes the given interpreter with the original program as
-argument, as binfmt_java and binfmt_em86 and binfmt_mz do.
-Since binfmt_misc does not define any default binary-formats, you have to
-register an additional binary-format.
-
-There are two general files in binfmt_misc and one file per registered
-format. The two general files are register and status.
-
-Registering a new binary format
-
-echo :name:type:offset:magic:mask:interpreter: > /proc/sys/fs/binfmt_misc/register
-
-with appropriate name (the name for the /proc-dir entry), offset
-(defaults to 0, if omitted), magic and mask (which can be omitted,
-defaults to all 0xff) and last but not least, the interpreter that is
-to be invoked (for example and testing '/bin/echo'). Type can be M for
-usual magic matching or E for filename extension matching (give
-extension in place of magic).
-
-To check or reset the status of the binary format handler:
-
-If you do a cat on the file /proc/sys/fs/binfmt_misc/status, you will
-get the current status (enabled/disabled) of binfmt_misc. Change the
-status by echoing 0 (disables) or 1 (enables) or -1 (caution: this
-clears all previously registered binary formats) to status. For
-example echo 0 > status to disable binfmt_misc (temporarily).
-
-Status of a single handler
-
-Each registered handler has an entry in /proc/sys/fs/binfmt_misc.
-These files perform the same function as status, but their scope is
-limited to the actual binary format. By cating this file, you also
-receive all related information about the interpreter/magic of the
-binfmt.
-
-Example usage of binfmt_misc (emulate binfmt_java)
-
-cd /proc/sys/fs/binfmt_misc
-echo ':Java:M::\xca\xfe\xba\xbe::/usr/local/java/bin/javawrapper:' > register
-echo ':HTML:E::html::/usr/local/java/bin/appletviewer:' > register
-echo ':Applet:M::<!--applet::/usr/local/java/bin/appletviewer:' > register
-echo ':DEXE:M::\x0eDEX::/usr/bin/dosexec:' > register
-
-These three lines add support for Java executables and Java applets
-(like binfmt_java, additionally recognizing the .html extension with
-no need to put <!--applet> to every applet file). You have to install
-the JDK and the shell-script /usr/local/java/bin/javawrapper too. It
-works around the brokenness of the Java filename handling. To add a
-Java binary, just create a link to the class-file somewhere in the
-path.
-
-3.4 /proc/sys/kernel - general kernel parameters
-
-This directory reflects general kernel behaviors. As I've said before,
-the contents are depend on your configuration. I'll list the most
-important files, along with descriptions of what they mean and how to
-use them.
-
-acct
- The file contains three values; highwater, lowwater, and
- frequency.
-
- It exists only when BSD-style process accounting is enabled. These
- values control its behavior. If the free space on the file system
- where the log lives goes below lowwater%, accounting suspends. If
- it goes above highwater%, accounting resumes. Frequency determines
- how often you check the amount of free space (value is in
- seconds). Default settings are: 4, 2, and 30. That is, suspend
- accounting if there left <= 2% free; resume it if we have a value
- >=3%; consider information about the amount of free space valid
- for 30 seconds
-
-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. However, when
- the value is > 0, Linux's reaction to this key combination will be
- an immediate reboot, without 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 is up to the program to decide
- what to do with it.
-
-domainname and hostname
- These files can be controlled to set the NIS domainname and
- hostname of your box. For the classic darkstar.frop.org a simple:
-
- # echo "darkstar" > /proc/sys/kernel/hostname
- # echo "frop.org" > /proc/sys/kernel/domainname
-
- would suffice to set your hostname and NIS domainname.
-
-osrelease, ostype and version
-
- The names make it pretty obvious what these fields contain:
-
- >cat /proc/sys/kernel/osrelease
- 2.1.131
- >cat /proc/sys/kernel/ostype
- Linux
- >cat /proc/sys/kernel/version
- #8 Mon Jan 25 19:45:02 PST 1999
-
- The files osrelease and ostype should be clear enough. Version
- needs a little more clarification however. The #8 means that this
- is the 8th 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.
-
-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. If set to 0, the auto
- reboot after a kernel panic is disabled, this is the default
- setting.
-
-printk
- The four values in printk denote console_loglevel,
- default_message_loglevel, minimum_console_level, and
- default_console_loglevel respectively.
-
- These values influence printk() behavior when printing or logging
- error messages, which come from inside the kernel. See syslog(2)
- for more information on the different log levels.
-
- 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 the console_loglevel can be set.
-
- default_console_loglevel
- Default value for console_loglevel.
-
-sg-big-buff
- This file shows the size of the generic SCSI (sg) buffer. At this
- point, you can't tune it yet, but you can change it at compile time
- by editing include/scsi/sg.h and changing the value of
- SG_BIG_BUFF.
-
- If you use a scanner with SANE (Scanner Access now easy) you
- might want to set this to a higher value. Look into the SANE
- documentation on this issue.
-
-modprobe
- The location where the modprobe binary is located. The kernel
- uses this program to load modules on demand.
-
-3.5 /proc/sys/vm - The virtual memory subsystem
-
-The files in this directory can be used to tune the operation of the
-virtual memory (VM) subsystem of the Linux kernel. In addition, one of
-the files (bdflush) has a little influence on disk usage.
-
-bdflush
- This file controls the operation of the bdflush kernel daemon. It
- currently contains 9 integer values, 6 of which are actually used
- by the kernel:
-
- nfract Percentage of buffer cache dirty to
- activate bdflush
- ndirty Maximum number of dirty blocks to
- write out per-wake-cycle
- nrefill Number of clean buffers to try to obtain
- each time we call refill
- nref_dirt Dirty buffer threshold for activating bdflush
- when trying to refill buffers.
- dummy unused
- age_buffer Time for normal buffer to age before you flush it
- age_super Time for superblock to age before you flush it
- dummy unused
- dummy unused
-
- nfract
- This parameter governs the maximum number of dirty buffers
- in the buffer cache. Dirty means that the contents of the
- buffer still have to be written to disk (as opposed to a
- clean buffer, which can just be forgotten about). Setting
- this to a high value means that Linux can delay disk writes
- for a long time, but it also means that it will have to do a
- lot of I/O at once when memory becomes short. A low value
- will spread out disk I/O more evenly.
-
- ndirty
- Ndirty gives the maximum number of dirty buffers that
- bdflush can write to the disk at one time. A high value will
- mean delayed, bursty I/O, while a small value can lead to
- memory shortage when bdflush isn't woken up often enough.
-
- nrefill
- This the number of buffers that bdflush will add to the list
- of free buffers when refill_freelist() is called. It is
- necessary to allocate free buffers beforehand, since the
- buffers are often different sizes than the memory pages
- and some bookkeeping needs to be done beforehand. The
- higher the number, the more memory will be wasted and the
- less often refill_freelist() will need to run.
-
- nref_dirt
- When refill_freelist() comes across more than nref_dirt
- dirty buffers, it will wake up bdflush.
-
- age_buffer and age_super
- Finally, the age_buffer and age_super parameters govern the
- maximum time Linux waits before writing out a dirty buffer
- to disk. The value is expressed in jiffies (clockticks), the
- number of jiffies per second is 100. Age_buffer is the
- maximum age for data blocks, while age_super is for
- filesystems meta data.
-
-buffermem
- The three values in this file control how much memory should be
- used for buffer memory. The percentage is calculated as a
- percentage of total system memory.
-
- The values are:
-
- min_percent
- This is the minimum percentage of memory that should be
- spent on buffer memory.
-
- borrow_percent
- When Linux is short on memory, and the buffer cache uses more
- than it has been allotted, the memory mangement (MM) subsystem
- will prune the buffer cache more heavily than other memory to
- compensate.
-
- max_percent
- This is the maximum amount of memory that can be used for
- buffer memory.
-
-freepages
- This file contains three values: min, low and high:
-
- min
- When the number of free pages in the system reaches this number,
- only the kernel can allocate more memory.
-
- low
- If the number of free pages gets below this point, the kernel
- starts swapping aggressively.
-
- high
- The kernel tries to keep up to this amount of memory free; if
- memory comes below this point, the kernel gently starts swapping
- in the hopes that it never has to do really aggressive swapping.
-
-kswapd
- Kswapd is the kernel swap out daemon. That is, kswapd is that piece
- of the kernel that frees memory when it gets fragmented or
- full. Since every system is different, you'll probably want some
- control over this piece of the system.
-
- The file contains three numbers:
-
- tries_base
- The maximum number of pages kswapd tries to free in one round is
- calculated from this number. Usually this number will be divided
- by 4 or 8 (see mm/vmscan.c), so it isn't as big as it looks.
-
- When you need to increase the bandwidth to/from swap, you'll want
- to increase this number.
-
- tries_min
- This is the minimum number of times kswapd tries to free a page
- each time it is called. Basically it's just there to make sure
- that kswapd frees some pages even when it's being called with
- minimum priority.
-
-
- swap_cluster
- This is probably the greatest influence on system
- performance. swap_cluster is the number of pages kswapd writes in
- one turn. You'll want this value to be large so that kswapd does
- its I/O in large chunks and the disk doesn't have to seek as
- often., but you don't want it to be too large since that would
- flood the request queue.
-
-overcommit_memory
- This file contains one value. The following algorithm is used to
- decide if there's enough memory: if the value of overcommit_memory
- is positive, then there's always enough memory. This is a useful
- feature, since programs often malloc() huge amounts of memory 'just
- in case', while they only use a small part of it. Leaving this
- value at 0 will lead to the failure of such a huge malloc(), when
- in fact the system has enough memory for the program to run.
-
- On the other hand, enabling this feature can cause you to run out
- of memory and thrash the system to death, so large and/or important
- servers will want to set this value to 0.
-
-pagecache
- This file does exactly the same as buffermem, only this file
- controls the amount of memory allowed for memory mapping and
- generic caching of files.
-
- You don't want the minimum level to be too low, otherwise your
- system might thrash when memory is tight or fragmentation is
- high.
-
-pagetable_cache
- The kernel keeps a number of page tables in a per-processor cache
- (this helps a lot on SMP systems). The cache size for each
- processor will be between the low and the high value.
-
- On a low-memory, single CPU system, you can safely set these values
- to 0 so you don't waste memory. It is used on SMP systems so that
- the system can perform fast pagetable allocations without having to
- aquire the kernel memory lock.
-
- For large systems, the settings are probably fine. For normal
- systems they won't hurt a bit. For small systems (<16MB ram) it
- might be advantageous to set both values to 0.
-
-swapctl
- This file contains no less than 8 variables. All of these values
- are used by kswapd.
-
- The first four variables sc_max_page_age, sc_page_advance,
- sc_page_decline and sc_page_initial_age are used to keep track of
- Linux's page aging. Page aging is a bookkeeping method to track
- which pages of memory are often used, and which pages can be
- swapped out without consequences.
-
- When a page is swapped in, it starts at sc_page_initial_age
- (default 3) and when the page is scanned by kswapd, its age is
- adjusted according to the following scheme:
-
- o If the page was used since the last time we scanned, its age
- is increased by sc_page_advance (default 3) up to a
- maximum of sc_max_page_age (default 20).
-
- o Else (meaning it wasn't used) its age is decreased by
- sc_page_decline (default 1).
-
- When a page reaches age 0, it's ready to be swapped out.
-
- The next four variables sc_age_cluster_fract, sc_age_cluster_min,
- sc_pageout_weight and sc_bufferout_weight, can be used to control
- kswapd's aggressiveness in swapping out pages.
-
- Sc_age_cluster_fract is used to calculate how many pages from a
- process are to be scanned by kswapd. The formula used is
-
- sc_age_cluster_fract
- -------------------- * resident set size
- 1024 =20
-
- So if you want kswapd to scan the whole process,
- sc_age_cluster_fract needs to have a value of 1024. The minimum
- number of pages kswapd will scan is represented by
- sc_age_cluster_min, this is done so kswapd will also scan small
- processes.
-
- The values of sc_pageout_weight and sc_bufferout_weight are used
- to control how many tries kswapd will make in order to swap out
- one page/buffer. These values can be used to fine-tune the ratio
- between user pages and buffer/cache memory. When you find that
- your Linux system is swapping out too many process pages in order
- to satisfy buffer memory demands, you might want to either
- increase sc_bufferout_weight, or decrease the value of
- sc_pageout_weight.
-
-3.6 /proc/sys/dev - Device specific parameters
-
-Currently there is only support for CDROM drives, and for those, there
-is only one read only file containing information about the CD-ROM
-drives attached to the system:
-
->cat /proc/sys/dev/cdrom/info
-CD-ROM information
-
-drive name: sr0 hdc
-drive speed: 0 6
-drive # of slots: 1 0
-Can close tray: 1 1
-Can open tray: 1 1
-Can lock tray: 1 1
-Can change speed: 1 1
-Can select disk: 0 1
-Can read multisession: 1 1
-Can read MCN: 1 1
-Reports media changed: 1 1
-Can play audio: 1 1
-
-You see two drives, sr0 and hdc, and their lists of features.
-
-3.7 /proc/sys/sunrpc - Remote procedure calls
-
-This directory contains four files, which enable or disable debugging
-for the RPC functions NFS, NFS-daemon, RPC and NLM. The default values
-are 0. They can be set to one, to turn debugging on. (The default
-value is 0 for each)
-
-3.8 /proc/sys/net - Networking stuff
-
-The interface to the networking parts of the kernel is located in
-/proc/sys/net. The table below shows all possible subdirectories. You
-may see only some of them, depending on the configuration of your
-kernel:
-
-+-------------------------------------------------------------+
-| core General parameter |appletalk Appletalk protocol |
-| unix Unix domain sockets |netrom NET/ROM |
-| 802 E802 protocol |ax25 AX25 |
-| ethernet Ethernet protocol |rose X.25 PLP layer |
-| ipv4 IP version 4 |x25 X.25 protocol |
-| ipx IPX |token-ring IBM token ring |
-| bridge Bridging |decnet DEC net |
-| ipv6 IP version 6 | |
-+-------------------------------------------------------------+
-
-We will concentrate on IP networking here. As AX15, X.25, and DEC Net
-are only minor players in the Linux world, we'll skip them in this
-chapter. You'll find some short info to Appletalk and IPX further down
-in section 3.10 and 3.11. Please look in the online documentation and
-the kernel source to get a detailed view of the parameters for those
-protocols. In this section we'll discuss the subdirectories printed in
-bold letters in the table above. As default values are suitable for
-most needs, there is no need to change these values.
-
-/proc/sys/net/core - Network core options
-
-rmem_default
- The default setting of the socket receive buffer in bytes.
-
-rmem_max
- The maximum receive socket buffer size in bytes.
-
-wmem_default
- The default setting (in bytes) of the socket send buffer.
-
-wmem_max
- The maximum send socket buffer size in bytes.
-
-message_burst and message_cost
- These parameters are used to limit the warning messages written to
- the kernel log from the networking code. They enforce a rate limit
- to make a denial-of-service attack impossible. The higher the
- message_cost factor is, the less messages will be
- written. Message_burst controls when messages will be dropped. The
- default settings limit warning messages to one every five seconds.
-
-netdev_max_backlog
- Maximal number of packets, queued on INPUT side, when the interface
- receives packets faster than kernel can process them.
-
-optmem_max
- Maximum ancillary buffer size allowed per socket. Ancillary data is
- a sequence of struct cmsghdr structures with appended data.
-
-/proc/sys/net/unix - Parameters for UNIX domain sockets
-
-There are only two files in this subdirectory. They control the delays
-for deleting and destroying socket descriptors.
-
-3.9 /proc/sys/net/ipv4 - IPV4 settings
-
-IP version 4 is still the most used protocol in Unix networking. It
-will be replaced by IP version 6 in the next couple of years, but for
-the moment it's the de facto standard for the internet and is used in
-most networking environments around the world. Because of the
-importance of this protocol, we'll have a deeper look into the subtree
-controlling the behavior of the IPv4 subsystem of the Linux kernel.
-
-Let's start with the entries in /proc/sys/net/ipv4 itself.
-
-ICMP settings
-
-icmp_echo_ignore_all and icmp_echo_ignore_broadcasts
- Turn on (1) or off (0), if the kernel should ignore all ICMP ECHO
- requests, or just those to broadcast and multicast addresses.
-
- Please note that if you accept ICMP echo requests with a
- broadcast/multicast destination address your network may be used
- as an exploder for denial of service packet flooding attacks to
- other hosts.
-
-icmp_destunreach_rate, icmp_echoreply_rate,
-icmp_paramprob_rate and icmp_timeexeed_rate
- Sets limits for sending ICMP packets to specific targets. A value of
- zero disables all limiting. Any positive value sets the maximum
- package rate in hundredths of a second (on Intel systems).
-
-IP settings
-
-ip_autoconfig
- This file contains one, if the host got its IP configuration by
- RARP, BOOTP, DHCP or a similar mechanism. Otherwise it is zero.
-
-ip_default_ttl
- TTL (Time To Live) for IPv4 interfaces. This is simply the
- maximum number of hops a packet may travel.
-
-ip_dynaddr
- Enable dynamic socket address rewriting on interface address change. This
- is useful for dialup interface with changing IP addresses.
-
-ip_forward
- Enable or disable forwarding of IP packages between interfaces. A
- change of this value resets all other parameters to their default
- values. They differ if the kernel is configured as host or router.
-
-ip_local_port_range
- Range of ports used by TCP and UDP to choose the local
- port. Contains two numbers, the first number is the lowest port,
- the second number the highest local port. Default is 1024-4999.
- Should be changed to 32768-61000 for high-usage systems.
-
-ip_no_pmtu_disc
- Global switch to turn path MTU discovery off. It can also be set
- on a per socket basis by the applications or on a per route
- basis.
-
-ip_masq_debug
- Enable/disable debugging of IP masquerading.
-
-
-IP fragmentation settings
-
-ipfrag_high_trash and ipfrag_low_trash
- Maximum memory used to reassemble IP fragments. When
- ipfrag_high_thresh bytes of memory is allocated for this purpose,
- the fragment handler will toss packets until ipfrag_low_thresh is
- reached.
-
-
-ipfrag_time
- Time in seconds to keep an IP fragment in memory.
-
-TCP settings
-
-tcp_retrans_collapse
- Bug-to-bug compatibility with some broken printers. On retransmit
- try to send bigger packets to work around bugs in certain TCP
- stacks. Can be turned off by setting it to zero.
-
-tcp_keepalive_probes
- Number of keep alive probes TCP sends out, until it decides that the
- connection is broken.
-
-tcp_keepalive_time
- How often TCP sends out keep alive messages, when keep alive is
- enabled. The default is 2 hours.
-
-tcp_syn_retries
- Number of times initial SYNs for a TCP connection attempt will be
- retransmitted. Should not be higher than 255. This is only the
- timeout for outgoing connections, for incoming connections the
- number of retransmits is defined by tcp_retries1.
-
-tcp_sack
- Enable select acknowledgments after RFC2018.
-
-tcp_timestamps
- Enable timestamps as defined in RFC1323.
-
-tcp_stdurg
- Enable the strict RFC793 interpretation of the TCP urgent pointer
- field. The default is to use the BSD compatible interpretation
- of the urgent pointer pointing to the first byte after the urgent
- data. The RFC793 interpretation is to have it point to the last
- byte of urgent data. Enabling this option may lead to
- interoperatibility problems. Disabled by default.
-
-tcp_syncookies
- Only valid when the kernel was compiled with
- CONFIG_SYNCOOKIES. Send out syncookies when the syn backlog queue
- of a socket overflows. This is to prevent against the common 'syn
- flood attack'. Disabled by default.
-
- Note that the concept of a socket backlog is abandoned, this
- means the peer may not receive reliable error messages from an
- over loaded server with syncookies enabled.
-
-tcp_window_scaling
- Enable window scaling as defined in RFC1323.
-
-tcp_fin_timeout
- How many seconds to wait for a final FIN before the socket is
- always closed. This is strictly a violation of the TCP
- specification, but required to prevent denial-of-service attacks.
-
-tcp_max_ka_probes
- How many keepalive probes are sent per slow timer run. Shouldn't be
- set too high to prevent bursts.
-
-tcp_max_syn_backlog
- Length of the per socket backlog queue. Since Linux 2.2 the backlog
- specified in listen(2) only specifies the length of the backlog
- queue of already established sockets. When more connection requests
- arrive Linux starts to drop packets. When syncookies are enabled
- the packets are still answered and the maximum queue is effectively
- ignored.
-
-tcp_retries1
- Defines how often an answer to a TCP connection request is
- retransmitted before giving up.
-
-tcp_retries2
- Defines how often a TCP packet is retransmitted before giving up.
-
-Interface specific settings
-
-In the directory /proc/sys/net/ipv4/conf you'll find one subdirectory
-for each interface the system knows about and one directory calls
-all. Changes in the all subdirectory affect all interfaces, where
-changes in the other subdirectories affect only one interface.
-
-All directories have the same entries:
-
-accept_redirects
- This switch decides if the kernel accepts ICMP redirect messages
- or not. The default is 'yes', if the kernel is configured for a
- regular host; and 'no' for a router configuration.
-
-accept_source_route
- Should source routed packages be accepted or declined. The
- default is dependent on the kernel configuration. It's 'yes' for
- routers and 'no' for hosts.
-
-bootp_relay
- Accept packets with source address 0.b.c.d destined not to this
- host as local ones. It is supposed that BOOTP relay daemon will
- catch and forward such packets.
-
- The default is 'no', as this feature is not implemented yet
- (kernel version 2.2.0-pre?).
-
-forwarding
- Enable or disable IP forwarding on this interface.
-
-log_martians
- Log packets with source addresses with no known route to kernel log.
-
-mc_forwarding
- Do multicast routing. The kernel needs to be compiled with
- CONFIG_MROUTE and a multicast routing daemon is required.
-
-proxy_arp
- Do (1) or don't (0) do proxy ARP.
-
-rp_filter
- Integer value deciding if source validation should be made.
- 1 means yes, 0 means no. Disabled by default, but
- local/broadcast address spoofing is always on.
-
- If you set this to 1 on a router that is the only connection
- for a network to the net , it evidently prevents spoofing attacks
- against your internal networks (external addresses can still be
- spoofed), without the need for additional firewall rules.
-
-secure_redirects
- Accept ICMP redirect messages only for gateways, listed in
- default gateway list. Enabled by default.
-
-shared_media
- If it is not set the kernel does not assume that different subnets
- on this device can communicate directly. Default setting is 'yes'.
-
-send_redirects
- Determines if or if not to send ICMP redirects to other hosts.
-
-
-Routing settings
-
-The directory /proc/sys/net/ipv4/route contains several file to
-control routing issues.
-
-error_burst and error_cost
- These parameters are used to limit the warning messages written to
- the kernel log from the routing code. The higher the error_cost
- factor is, the fewer messages will be written. Error_burst controls
- when messages will be dropped. The default settings limit warning
- messages to one every five seconds.
-
-flush
- Writing to this file results in a flush of the routing cache.
-
-gc_elastic, gc_interval, gc_min_interval, gc_tresh, gc_timeout
- Values to control the frequency and behavior of the garbage
- collection algorithm for the routing cache.
-
-max_size
- Maximum size of the routing cache. Old entries will be purged
- once the cache has this size.
-
-max_delay, min_delay
- Delays for flushing the routing cache.
-
-redirect_load, redirect_number
- Factors which determine if more ICPM redirects should be sent to
- a specific host. No redirects will be sent once the load limit or
- the maximum number of redirects has been reached.
-
-redirect_silence
-
- Timeout for redirects. After this period redirects will be sent
- again, even if this has been stopped, because the load or number
- limit has been reached.
-
-Network Neighbor handling
-
-Settings about how to handle connections with direct neighbors (nodes
-attached to the same link) can be found in the directory
-/proc/sys/net/ipv4/neigh.
-
-As we saw it in the conf directory, there is a default subdirectory
-which holds the default values, and one directory for each
-interface. The contents of the directories are identical, with the
-single exception that the default settings contain additional options
-to set garbage collection parameters.
-
-In the interface directories you'll find the following entries:
-
-base_reachable_time
- A base value used for computing the random reachable time value
- as specified in RFC2461.
-
-retrans_time
- The time, expressed in jiffies (1/100 sec), between retransmitted
- Neighbor Solicitation messages. Used for address resolution and to
- determine if a neighbor is unreachable.
-
-unres_qlen
- Maximum queue length for a pending arp request - how many packets
- are accepted from other layers while the arp address is still
- resolved.
-
-anycast_delay
- Maximum for random delay of answers to neighbor solicitation
- messages in jiffies (1/100 sec). Not yet implemented (Linux does
- not have anycast support yet).
-
-ucast_solicit
- Maximum number of retries for unicast solicitation.
-
-mcast_solicit
- Maximum number of retries for multicast solicitation.
-
-delay_first_probe_time
- Delay for the first time probe if the neighbor is reachable. (see
- gc_stale_time).
-
-locktime
- An ARP/neighbor entry is only replaced with a new one if the old
- is at least locktime old. This prevents ARP cache thrashing.
-
-proxy_delay
- Maximum time (real time is random [0..proxytime]) before
- answering to an arp request for which we have an proxy arp entry.
- In some cases, this is used to prevent network flooding.
-
-proxy_qlen
- Maximum queue length of the delayed proxy arp timer (see
- proxy_delay).
-
-app_solcit
- Determines the number of requests to send to the user level arp
- daemon. 0 to turn off.
-
-gc_stale_time
- Determines how often to check for stale ARP entries. After an ARP
- entry is stale it will be resolved again (useful when an IP address
- migrates to another machine). When ucast_solicit is > 0 it first
- tries to send an ARP packet directly to the known host, when that
- fails and mcast_solicit is > 0, an ARP request is broadcasted.
-
-3.10 Appletalk
-
-The /proc/sys/net/appletalk directory holds the Appletalk
-configuration data when Appletalk is loaded. The configurable
-parameters are:
-
-aarp-expiry-time
- The amount of time we keep an AARP entry before expiring
- it. Used to age out old hosts.
-
-aarp-resolve-time
- The amount of time we will spend trying to resolve an Appletalk
- address.
-
-aarp-retransmit-limit
- The number of times we will retransmit a query before giving up.
-
-aarp-tick-time
- Controls the rate at which expiries are checked.
-
-
-The directory /proc/net/appletalk holds the list of active appletalk
-sockets on a machine.
-
-The fields indicate the DDP type, the local address (in network:node
-format) the remote address, the size of the transmit pending queue,
-the size of the received queue (bytes waiting for applications to
-read) the state and the uid owning the socket.
-
-/proc/net/atalk_iface lists all the interfaces configured for
-appletalk.It shows the name of the interface, its appletalk address,
-the network range on that ad- dress (or network number for phase 1
-networks), and the status of the interface.
-
-/proc/net/atalk_route lists each known network route. It lists the
-target (network) that the route leads to, the router (may be directly
-connected), the route flags, and the device the route is via.
-
-3.11 IPX
-
-The IPX protocol has no tunable values in /proc/sys/net.
-
-The IPX protocol does, however, provide /proc/net/ipx. This lists each
-IPX socket giving the local and remote addresses in Novell format
-(that is network:node:port). In accordance with the strange Novell
-tradition, everything but the port is in hex. Not_Connected is
-displayed for sockets that are not tied to a specific remote
-address. The Tx and Rx queue sizes indicate the number of bytes
-pending for transmit and receive. The state indicates the state the
-socket is in and the uid is the owning uid of the socket.
-
-The /proc/net/ipx_interface file lists all IPX interfaces. For each
-interface it gives the network number, the node number, and indicates
-if the network is the primary network. It also indicates which device it is bound to (or
-Internal for internal networks) and the Frame Type if
-appropriate. Linux supports 802.3, 802.2, 802.2 SNAP and DIX (Blue
-Book) ethernet framing for IPX.
-
-The /proc/net/ipx_route table holds a list of IPX routes. For each
-route it gives the destination network, the router node (or Directly)
-and the network address of the router (or Connected) for internal
-networks.
FUNET's LINUX-ADM group, linux-adm@nic.funet.fi
TCL-scripts by Sam Shen (who was at: slshen@lbl.gov)