View Source: SysctlNotes - Waikato Linux Users Group

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!!How to Edit Kernel Parameters During Runtime

!List all available kernel parameters and their values:
Note : They are all listed under /proc/sys

*sysctl -a

!Modify the value of a kernel parameter:

*sysctl -w variable=value

For example say I do not want my host to respond to pings (note that this is recommended):
This can be done by telling the kernel to ignore all ICMP ECHO_REQUEST's

*sysctl -w net.ipv4.icmp_echo_ignore_all=1

OR

*sysctl -w net/ipv4/icmp_echo_ignore_all=1

Notes :

1. Setting this variable to 1 (or anything other than 0) will make the kernel ignore ICMP echo request's.

2. The 'net.ipv4.icmp_echo_ignore_all' part above specifies the path inside /proc/sys/ to the file corresponding to the kernel parameter. If you use cat to take a look inside this file you will see that all in contains is '1' (the value of the kernel variable)

If you want to save these in a file it's usually in /etc/sysctl.conf (see [sysctl.conf(5)])

There is also another filesystem full of kernel parameters in called SysFs, normally mounted at /sys. SysFs has more details.
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CategoryNotes
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See also [sysctl(8)], [sysctl(2)], SysControls, SysFs

One page links to SysctlNotes:

SysControls

Last edited on Thursday, June 14, 2007 10:20:25 am by JamieCurtis

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