Editing Sysctl
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The [https://www.freebsd.org/cgi/man.cgi?query=sysctl&apropos=0&sektion=0&manpath=FreeBSD+12.1-RELEASE+and+Ports&arch=default&format=html sysctl] utility retrieves kernel state and allows processes with appropriate privilege to set kernel state. The state to be retrieved or set is described using a “Management Information Base” (“MIB”) style name, described as a dotted set of components.<br/> | The [https://www.freebsd.org/cgi/man.cgi?query=sysctl&apropos=0&sektion=0&manpath=FreeBSD+12.1-RELEASE+and+Ports&arch=default&format=html sysctl] utility retrieves kernel state and allows processes with appropriate privilege to set kernel state. The state to be retrieved or set is described using a “Management Information Base” (“MIB”) style name, described as a dotted set of components.<br/> | ||
− | == | + | ==Usage== |
The information available from sysctl consists of integers, strings, and opaque types. The sysctl utility only knows about a couple of opaque types, and will resort to hexdumps for the rest. The opaque information is much more useful if retrieved by special purpose programs such as [https://www.freebsd.org/cgi/man.cgi?query=ps&sektion=1&apropos=0&manpath=FreeBSD+12.1-RELEASE+and+Ports ps(1)], [https://www.freebsd.org/cgi/man.cgi?query=systat&sektion=1&apropos=0&manpath=FreeBSD+12.1-RELEASE+and+Ports systat(1)], and [https://www.freebsd.org/cgi/man.cgi?query=netstat&sektion=1&apropos=0&manpath=FreeBSD+12.1-RELEASE+and+Ports netstat(1)]. | The information available from sysctl consists of integers, strings, and opaque types. The sysctl utility only knows about a couple of opaque types, and will resort to hexdumps for the rest. The opaque information is much more useful if retrieved by special purpose programs such as [https://www.freebsd.org/cgi/man.cgi?query=ps&sektion=1&apropos=0&manpath=FreeBSD+12.1-RELEASE+and+Ports ps(1)], [https://www.freebsd.org/cgi/man.cgi?query=systat&sektion=1&apropos=0&manpath=FreeBSD+12.1-RELEASE+and+Ports systat(1)], and [https://www.freebsd.org/cgi/man.cgi?query=netstat&sektion=1&apropos=0&manpath=FreeBSD+12.1-RELEASE+and+Ports netstat(1)]. | ||
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Some of the variables which cannot be modified during normal system operation can be initialized via [https://www.freebsd.org/cgi/man.cgi?query=loader&sektion=8&apropos=0&manpath=FreeBSD+12.1-RELEASE+and+Ports loader(8)] tunables. This can for example be done by setting them in [https://www.freebsd.org/cgi/man.cgi?query=loader.conf&sektion=5&apropos=0&manpath=FreeBSD+12.1-RELEASE+and+Ports loader.conf(5)]. Please refer to [https://www.freebsd.org/cgi/man.cgi?query=loader.conf&sektion=5&apropos=0&manpath=FreeBSD+12.1-RELEASE+and+Ports loader.conf(5)] for more information on which tunables are available and how to set them. | Some of the variables which cannot be modified during normal system operation can be initialized via [https://www.freebsd.org/cgi/man.cgi?query=loader&sektion=8&apropos=0&manpath=FreeBSD+12.1-RELEASE+and+Ports loader(8)] tunables. This can for example be done by setting them in [https://www.freebsd.org/cgi/man.cgi?query=loader.conf&sektion=5&apropos=0&manpath=FreeBSD+12.1-RELEASE+and+Ports loader.conf(5)]. Please refer to [https://www.freebsd.org/cgi/man.cgi?query=loader.conf&sektion=5&apropos=0&manpath=FreeBSD+12.1-RELEASE+and+Ports loader.conf(5)] for more information on which tunables are available and how to set them. | ||
− | + | ===Retrieve Kernel Information=== | |
+ | |||
+ | |||
+ | Use '''sysctl''' plus the following sysctl variable NAME: | ||
<code>sysctl NAME</code> | <code>sysctl NAME</code> | ||
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|} | |} | ||
− | ==Categories of Kernel information== | + | ===Categories of Kernel information=== |
The kernel information are organized in a tree format, called as ''management information base (MIB) with several categories. Compare the following list with the NAMEs above. | The kernel information are organized in a tree format, called as ''management information base (MIB) with several categories. Compare the following list with the NAMEs above. | ||
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'''Example:''' the category ''kern'' and its subcategory ''hostname'' give you: ''kern.hostname'' a unique sysctl variable. | '''Example:''' the category ''kern'' and its subcategory ''hostname'' give you: ''kern.hostname'' a unique sysctl variable. | ||
− | ==Retrieve Definition of a sysctl Variable== | + | ===Retrieve Definition of a sysctl Variable=== |
If you like to know how is the sysctl variable defined, you have to use the following command: | If you like to know how is the sysctl variable defined, you have to use the following command: | ||
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More variables than in [https://www.freebsd.org/cgi/man.cgi?query=sysctl&apropos=0&sektion=0&manpath=FreeBSD+12.1-RELEASE+and+Ports&arch=default&format=html sysctl(8)] exist and the best and likely only place to search for their deeper meaning is undoubtedly the source where they are | More variables than in [https://www.freebsd.org/cgi/man.cgi?query=sysctl&apropos=0&sektion=0&manpath=FreeBSD+12.1-RELEASE+and+Ports&arch=default&format=html sysctl(8)] exist and the best and likely only place to search for their deeper meaning is undoubtedly the source where they are | ||
defined. | defined. | ||
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[[Category:How To]] | [[Category:How To]] | ||
[[Category:Kernel]] | [[Category:Kernel]] |