The software described in this documentation is either in Extended Support or Sustaining Support. See https://www.oracle.com/us/support/library/enterprise-linux-support-policies-069172.pdf for more information.
Oracle recommends that you upgrade the software described by this documentation as soon as possible.
Some virtual files under /proc, and under
/proc/sys in particular, are writable and you
can use them to adjust settings in the kernel. For example, to
change the host name, you can write a new value to
/proc/sys/kernel/hostname:
# echo www.mydomain.com > /proc/sys/kernel/hostname
Other files take value that take binary or Boolean values. For
example, the value of
/proc/sys/net/ipv4/ip_forward determines
whether the kernel forwards IPv4 network packets.
#cat /proc/sys/net/ipv4/ip_forward0 #echo 1 > /proc/sys/net/ipv4/ip_forward#cat /proc/sys/net/ipv4/ip_forward1
You can use the sysctl command to view or
modify values under the /proc/sys directory.
Even root cannot bypass the file access
permissions of virtual file entries under
/proc. If you attempt to change the value
of a read-only entry such as
/proc/partitions, there is no kernel code
to service the write() system call.
To display all of the current kernel settings:
# sysctl -a
kernel.sched_child_runs_first = 0
kernel.sched_min_granularity_ns = 2000000
kernel.sched_latency_ns = 10000000
kernel.sched_wakeup_granularity_ns = 2000000
kernel.sched_shares_ratelimit = 500000
...
The delimiter character in the name of a setting is a period
(.) rather than a slash
(/) in a path relative to
/proc/sys. For example,
net.ipv4.ip_forward represents
net/ipv4/ip_forward and
kernel.msgmax represents
kernel/msgmax.
To display an individual setting, specify its name as the argument to sysctl:
# sysctl net.ipv4.ip_forward
net.ipv4.ip_forward = 0To change the value of a setting, use the following form of the command:
# sysctl -w net.ipv4.ip_forward=1
net.ipv4.ip_forward = 1
Changes that you make in this way remain in force only until the
system is rebooted. To make configuration changes persist after
the system is rebooted, you must add them to the
/etc/sysctl.conf file. Any changes that you
make to this file take effect when the system reboots or if you
run the sysctl -p command, for example:
#sed -i '/net.ipv4.ip_forward/s/= 0/= 1/' /etc/sysctl.conf#grep ip_forward /etc/sysctl.confnet.ipv4.ip_forward = 1 #sysctl net.ipv4.ip_forwardnet.ipv4.ip_forward = 0 #sysctl -pnet.ipv4.ip_forward = 1 net.ipv4.conf.default.rp_filter = 1 ... kernel.shmall = 4294967296 #sysctl net.ipv4.ip_forwardnet.ipv4.ip_forward = 1
For more information, see the sysctl(8) and
sysctl.conf(5) manual pages.