TEXT   53

kernel

Guest on 30th July 2022 12:40:45 AM

  1. Documentation for /proc/sys/kernel/*    kernel version 2.2.10
  2.         (c) Rik van Riel <riel@nl.linux.org>
  3.  
  4. For general info and legal blurb, please look in README.
  5.  
  6. ==============================================================
  7.  
  8. This file contains documentation for the sysctl files in
  9. /proc/sys/kernel/ and is valid for Linux kernel version 2.2.
  10.  
  11. The files in this directory can be used to tune and monitor
  12. miscellaneous and general things in the operation of the Linux
  13. kernel. Since some of the files _can_ be used to screw up your
  14. system, it is advisable to read both documentation and source
  15. before actually making adjustments.
  16.  
  17. Currently, these files might (depending on your configuration)
  18. show up in /proc/sys/kernel:
  19. - acct
  20. - ctrl-alt-del
  21. - dentry-state
  22. - domainname
  23. - hostname
  24. - htab-reclaim                [ PPC only ]
  25. - java-appletviewer           [ binfmt_java, obsolete ]
  26. - java-interpreter            [ binfmt_java, obsolete ]
  27. - l2cr                        [ PPC only ]
  28. - modprobe                    ==> Documentation/kmod.txt
  29. - osrelease
  30. - ostype
  31. - overflowgid
  32. - overflowuid
  33. - panic
  34. - powersave-nap               [ PPC only ]
  35. - printk
  36. - real-root-dev               ==> Documentation/initrd.txt
  37. - reboot-cmd                  [ SPARC only ]
  38. - rtsig-nr
  39. - rtsig-max
  40. - sg-big-buff                 [ generic SCSI device (sg) ]
  41. - shmmax                      [ sysv ipc ]
  42. - version
  43. - zero-paged                  [ PPC only ]
  44.  
  45. ==============================================================
  46.  
  47. acct:
  48.  
  49. highwater lowwater frequency
  50.  
  51. If BSD-style process accounting is enabled these values control
  52. its behaviour. If free space on filesystem where the log lives
  53. goes below <lowwater>% accounting suspends. If free space gets
  54. above <highwater>% accounting resumes. <Frequency> determines
  55. how often do we check the amount of free space (value is in
  56. seconds). Default:
  57. 4 2 30
  58. That is, suspend accounting if there left <= 2% free; resume it
  59. if we got >=4%; consider information about amount of free space
  60. valid for 30 seconds.
  61.  
  62. ==============================================================
  63.  
  64. ctrl-alt-del:
  65.  
  66. When the value in this file is 0, ctrl-alt-del is trapped and
  67. sent to the init(1) program to handle a graceful restart.
  68. When, however, the value is > 0, Linux's reaction to a Vulcan
  69. Nerve Pinch (tm) will be an immediate reboot, without even
  70. syncing its dirty buffers.
  71.  
  72. Note: when a program (like dosemu) has the keyboard in 'raw'
  73. mode, the ctrl-alt-del is intercepted by the program before it
  74. ever reaches the kernel tty layer, and it's up to the program
  75. to decide what to do with it.
  76.  
  77. ==============================================================
  78.  
  79. domainname & hostname:
  80.  
  81. These files can be used to set the NIS/YP domainname and the
  82. hostname of your box in exactly the same way as the commands
  83. domainname and hostname, i.e.:
  84. # echo "darkstar" > /proc/sys/kernel/hostname
  85. # echo "mydomain" > /proc/sys/kernel/domainname
  86. has the same effect as
  87. # hostname "darkstar" > /proc/sys/kernel/hostname
  88. # domainname "mydomain" > /proc/sys/kernel/domainname
  89.  
  90. Note, however, that the classic darkstar.frop.org has the
  91. hostname "darkstar" and DNS (Internet Domain Name Server)
  92. domainname "frop.org", not to be confused with the NIS (Network
  93. Information Service) or YP (Yellow Pages) domainname. These two
  94. domain names are in general different. For a detailed discussion
  95. see the hostname(1) man page.
  96.  
  97. ==============================================================
  98.  
  99. htab-reclaim: (PPC only)
  100.  
  101. Setting this to a non-zero value, the PowerPC htab
  102. (see Documentation/powerpc/ppc_htab.txt) is pruned
  103. each time the system hits the idle loop.
  104.  
  105. ==============================================================
  106.  
  107. l2cr: (PPC only)
  108.  
  109. This flag controls the L2 cache of G3 processor boards. If
  110. 0, the cache is disabled. Enabled if nonzero.
  111.  
  112. ==============================================================
  113.  
  114. osrelease, ostype & version:
  115.  
  116. # cat osrelease
  117. 2.1.88
  118. # cat ostype
  119. Linux
  120. # cat version
  121. #5 Wed Feb 25 21:49:24 MET 1998
  122.  
  123. The files osrelease and ostype should be clear enough. Version
  124. needs a little more clarification however. The '#5' means that
  125. this is the fifth kernel built from this source base and the
  126. date behind it indicates the time the kernel was built.
  127. The only way to tune these values is to rebuild the kernel :-)
  128.  
  129. ==============================================================
  130.  
  131. overflowgid & overflowuid:
  132.  
  133. if your architecture did not always support 32-bit UIDs (i.e. arm, i386,
  134. m68k, sh, and sparc32), a fixed UID and GID will be returned to
  135. applications that use the old 16-bit UID/GID system calls, if the actual
  136. UID or GID would exceed 65535.
  137.  
  138. These sysctls allow you to change the value of the fixed UID and GID.
  139. The default is 65534.
  140.  
  141. ==============================================================
  142.  
  143. panic:
  144.  
  145. The value in this file represents the number of seconds the
  146. kernel waits before rebooting on a panic. When you use the
  147. software watchdog, the recommended setting is 60.
  148.  
  149. ==============================================================
  150.  
  151. powersave-nap: (PPC only)
  152.  
  153. If set, Linux-PPC will use the 'nap' mode of powersaving,
  154. otherwise the 'doze' mode will be used.
  155.  
  156. ==============================================================
  157.  
  158. printk:
  159.  
  160. The four values in printk denote: console_loglevel,
  161. default_message_loglevel, minimum_console_level and
  162. default_console_loglevel respectively.
  163.  
  164. These values influence printk() behavior when printing or
  165. logging error messages. See 'man 2 syslog' for more info on
  166. the different loglevels.
  167.  
  168. - console_loglevel: messages with a higher priority than
  169.   this will be printed to the console
  170. - default_message_level: messages without an explicit priority
  171.   will be printed with this priority
  172. - minimum_console_loglevel: minimum (highest) value to which
  173.   console_loglevel can be set
  174. - default_console_loglevel: default value for console_loglevel
  175.  
  176. Note: a quick look in linux/kernel/printk.c will reveal that
  177. these variables aren't put inside a structure, so their order
  178. in-core isn't formally guaranteed and garbage values _might_
  179. occur when the compiler changes. (???)
  180.  
  181. ==============================================================
  182.  
  183. reboot-cmd: (Sparc only)
  184.  
  185. ??? This seems to be a way to give an argument to the Sparc
  186. ROM/Flash boot loader. Maybe to tell it what to do after
  187. rebooting. ???
  188.  
  189. ==============================================================
  190.  
  191. rtsig-max & rtsig-nr:
  192.  
  193. The file rtsig-max can be used to tune the maximum number
  194. of POSIX realtime (queued) signals that can be outstanding
  195. in the system.
  196.  
  197. Rtsig-nr shows the number of RT signals currently queued.
  198.  
  199. ==============================================================
  200.  
  201. sg-big-buff:
  202.  
  203. This file shows the size of the generic SCSI (sg) buffer.
  204. You can't tune it just yet, but you could change it on
  205. compile time by editing include/scsi/sg.h and changing
  206. the value of SG_BIG_BUFF.
  207.  
  208. There shouldn't be any reason to change this value. If
  209. you can come up with one, you probably know what you
  210. are doing anyway :)
  211.  
  212. ==============================================================
  213.  
  214. shmmax:
  215.  
  216. This value can be used to query and set the run time limit
  217. on the maximum shared memory segment size that can be created.
  218. Shared memory segments up to 1Gb are now supported in the
  219. kernel.  This value defaults to SHMMAX.
  220.  
  221. ==============================================================
  222.  
  223. zero-paged: (PPC only)
  224.  
  225. When enabled (non-zero), Linux-PPC will pre-zero pages in
  226. the idle loop, possibly speeding up get_free_pages. Since
  227. this only affects what the idle loop is doing, you should
  228. enable this and see if anything changes.

Raw Paste


Login or Register to edit or fork this paste. It's free.