What's the prescribed way to set Linux kernel runtime parameters? I've seen sometimes that people will set these in files such as
Is this really the right way to do this?
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You can use
sysctl to set some of the kernel parameters, specifically the ones under
/proc/sys. These can be set in the file
/etc/sysctl.conf or added to a single file (the preferred method on some distro's such as Fedora) in the directory
/etc/sysctl.d. On distros that have this directory it's meant for customization's.
excerpt from sysctl's man page
sysctl - configure kernel parameters at runtime
You can get a partial list of what kernel parameters are currently set using this command:
$ sudo sysctl -a | head -5 abi.vsyscall32 = 1 debug.exception-trace = 1 debug.kprobes-optimization = 1 dev.cdrom.autoclose = 1 dev.cdrom.autoeject = 0
Simply add rules to the file
# sysctl.conf sample # kernel.domainname = example.com ; this one has a space which will be written to the sysctl! kernel.modprobe = /sbin/mod probe
You can also use the
sysctl.conf command line to make edits to this file without having to edit it directly.
$ sysctl -w kernel.domainname="example.com"
After making any changes be sure to make them active.
$ sysctl -p
To add your override of this parameter simply put it in a file named similarly to the files that are already present in the
$ ls -l /etc/sysctl.d total 40 -rw-r--r-- 1 root root 77 Jul 16 2012 10-console-messages.conf -rw-r--r-- 1 root root 490 Jul 16 2012 10-ipv6-privacy.conf -rw-r--r-- 1 root root 726 Jul 16 2012 10-kernel-hardening.conf -rw-r--r-- 1 root root 1184 Jul 16 2012 10-magic-sysrq.conf -rw-r--r-- 1 root root 509 Jul 16 2012 10-network-security.conf ...
In a file named something like
$ more 10-console-messages.conf # the following stops low-level messages on console kernel.printk = 4 4 1 7
Where the name of the parameter is on the left, and it's corresponding value is on the right.
sysctl's man page for more details.