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[ikiwiki.git] / docs / handbook / handbook-configtuning-sysctl.mdwn
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5643fec9 3## 6.11 Tuning with sysctl
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7[sysctl(8)](http://leaf.dragonflybsd.org/cgi/web-man?command=sysctl&section=8) is an interface that allows you to make changes to a running DragonFly system. This includes many advanced options of the TCP/IP stack and virtual memory system that can dramatically improve performance for an experienced system administrator. Over five hundred system variables can be read and set using [sysctl(8)](http://leaf.dragonflybsd.org/cgi/web-man?command=sysctl&section=8).
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11At its core, [sysctl(8)](http://leaf.dragonflybsd.org/cgi/web-man?command=sysctl&section=8) serves two functions: to read and to modify system settings.
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15To view all readable variables:
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21 % sysctl -a
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27To read a particular variable, for example, `kern.maxproc`:
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33 % sysctl kern.maxproc
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35 kern.maxproc: 1044
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41To set a particular variable, use the intuitive `***variable***`=`***value***` syntax:
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47 # sysctl kern.maxfiles=5000
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49 kern.maxfiles: 2088 -< 5000
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55Settings of sysctl variables are usually either strings, numbers, or booleans (a boolean being `1` for yes or a `0` for no).
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59If you want to set automatically some variables each time the machine boots, add them to the `/etc/sysctl.conf` file. For more information see the [sysctl.conf(5)](http://leaf.dragonflybsd.org/cgi/web-man?command=sysctl.conf&section=5) manual page and the [configtuning-configfiles.html#CONFIGTUNING-SYSCTLCONF Section 6.10.4].
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63### 6.11.1 sysctl(8) Read-only
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67***Contributed by Tom Rhodes. ***
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71In some cases it may be desirable to modify read-only [sysctl(8)](http://leaf.dragonflybsd.org/cgi/web-man?command=sysctl&section=8) values. While this is not recommended, it is also sometimes unavoidable.
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75For instance on some laptop models the [cardbus(4)](http://leaf.dragonflybsd.org/cgi/web-man?command=cardbus&section=4) device will not probe memory ranges, and fail with errors which look similar to:
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81 cbb0: Could not map register memory
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83 device_probe_and_attach: cbb0 attach returned 12
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89Cases like the one above usually require the modification of some default [sysctl(8)](http://leaf.dragonflybsd.org/cgi/web-man?command=sysctl&section=8) settings which are set read only. To overcome these situations a user can put [sysctl(8)](http://leaf.dragonflybsd.org/cgi/web-man?command=sysctl&section=8) ***OIDs*** in their local `/boot/loader.conf`. Default settings are located in the `/boot/defaults/loader.conf` file.
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51e754f0 93Fixing the problem mentioned above would require a user to set `hw.pci.allow_unsupported_io_range=1` in the aforementioned file. Now [cardbus(4)](http://leaf.dragonflybsd.org/cgi/web-man?command=cardbus&section=4) will work properly.
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101CategoryHandbook
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103CategoryHandbook-configuration
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