Shulou(Shulou.com)06/01 Report--

This article introduces the relevant knowledge of "how to use the system parameter modification command sysctl in Linux". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Sysctl configuration and kernel parameters displayed in the / proc/sys directory. You can use sysctl to set or reset networking features such as IP forwarding, IP fragmentation, and source route checking. Users only need to edit the / etc/sysctl.conf file to perform the functions controlled by sysctl manually or automatically.

Command format:

Sysctl [- n] [- e]-w variable=value

Sysctl [- n] [- e]-p (default / etc/sysctl.conf)

Sysctl [- n] [- e]-a

The meaning of common parameters:

-w temporarily change the value of a specified parameter, such as

Sysctl-w net.ipv4.ip_forward=1

-a displays all system parameters

-p loads system parameters from the specified file, or from / etc/sysctl.conf if not specified

If you just want to change the value of a system parameter temporarily, you can do it in two ways, such as enabling IP routing forwarding:

1) # echo 1 > / proc/sys/net/ipv4/ip_forward

2) # sysctl-w net.ipv4.ip_forward=1

Both of the above methods may turn on the routing function immediately, but if the system restarts, or executes the

# service network restart

Command, the set value will be lost. If you want to keep the configuration permanently, you can modify the / etc/sysctl.conf file.

Change net.ipv4.ip_forward=0 to net.ipv4.ip_forward=1

Common usage

There are three ways to modify (configure)

Two kinds of temporary effect

The code is as follows:

# echo 1 > / proc/sys/net/ipv4/ip_forward / / enable routing

# sysctl-w net.ipv4.ip_forward=1 / / use this option to change a sysctl setting

If the system restarts, or if the service network restart command is executed, the set value will be lost

Everything in the / proc directory is temporary, so any changes will be lost after rebooting the system.

One kind of permanent effect

The code is as follows:

# vi / etc/sysctl.conf

Change the value of net.ipv4.ip_forward=0 to 1 / / to turn on packet forwarding.

The code is as follows:

# sysctl-p / etc/sysctl.conf / / reload / etc/sysctl.conf file. If no path is specified after-p, load / etc/sysctl.conf

The specified value is set after the system enters multi-user mode. Not all variables can be set in this mode.

The sysctl variable is usually set as a string, number, or Boolean. (Boolean means 1 for 'yes',' and 0 for 'no').

The code is as follows:

[root@Firewall sys] # sysctl-a / / View all parameters

[root@Firewall sys] # sysctl net.core.wmem_max / / View the specified parameters

Net.core.wmem_max = 131071

[root@Firewall sys] # sysctl net.core.wmem_max=256000 / / modify the specified parameters

Net.core.wmem_max = 256000

Example

All the parameters seen by sysctl-a come from the contents of the files in the / proc/sys/ directory. You can use the method of grep plus sort and ll to view the corresponding

The code is as follows:

[root@Firewall sys] # pwd

/ proc/sys

[root@Firewall sys] # ll

Total 0

Dr-xr-xr-x 0 root root 0 Apr 12 14:29 crypto

Dr-xr-xr-x 0 root root 0 May 10 15:53 debug

Dr-xr-xr-x 0 root root 0 Apr 12 14:28 dev

Dr-xr-xr-x 0 root root 0 Apr 12 14:28 fs

Dr-xr-xr-x 0 root root 0 Apr 12 14:28 kernel

Dr-xr-xr-x 0 root root 0 Apr 12 14:28 net

Dr-xr-xr-x 0 root root 0 May 10 15:53 sunrpc

Dr-xr-xr-x 0 root root 0 May 10 15:53 vm

The code is as follows:

[root@Firewall netfilter] # pwd

/ proc/sys/net/netfilter

[root@Firewall netfilter] # sysctl-a | grep net.net | sort

Net.netfilter.nf_conntrack_acct = 1

Net.netfilter.nf_conntrack_buckets = 16384

Net.netfilter.nf_conntrack_checksum = 1

Net.netfilter.nf_conntrack_count = 1739

Net.netfilter.nf_conntrack_expect_max = 256

Net.netfilter.nf_conntrack_generic_timeout = 600,

Net.netfilter.nf_conntrack_icmp_timeout = 30

Net.netfilter.nf_conntrack_log_invalid = 0

Net.netfilter.nf_conntrack_max = 65536

Net.netfilter.nf_conntrack_tcp_be_liberal = 0

Net.netfilter.nf_conntrack_tcp_loose = 1

Net.netfilter.nf_conntrack_tcp_max_retrans = 3

Net.netfilter.nf_conntrack_tcp_timeout_close = 10

Net.netfilter.nf_conntrack_tcp_timeout_close_wait = 60

Net.netfilter.nf_conntrack_tcp_timeout_established = 432000

Net.netfilter.nf_conntrack_tcp_timeout_fin_wait = 120

Net.netfilter.nf_conntrack_tcp_timeout_last_ack = 30

Net.netfilter.nf_conntrack_tcp_timeout_max_retrans = 300

Net.netfilter.nf_conntrack_tcp_timeout_syn_recv = 60

Net.netfilter.nf_conntrack_tcp_timeout_syn_sent = 120

Net.netfilter.nf_conntrack_tcp_timeout_time_wait = 120

Net.netfilter.nf_conntrack_tcp_timeout_unacknowledged = 300

Net.netfilter.nf_conntrack_udp_timeout = 30

Net.netfilter.nf_conntrack_udp_timeout_stream = 180

The code is as follows:

[root@Firewall netfilter] # ll

Total 0

-rw-r--r-- 1 root root 0 May 10 15:53 nf_conntrack_acct

-root root May 10 15:53 nf_conntrack_buckets

-rw-r--r-- 1 root root 0 May 10 15:53 nf_conntrack_checksum

-root root May 10 15:53 nf_conntrack_count

-rw-r--r-- 1 root root 0 May 10 15:53 nf_conntrack_expect_max

-rw-r--r-- 1 root root 0 May 10 15:53 nf_conntrack_generic_timeout

-rw-r--r-- 1 root root 0 May 10 15:53 nf_conntrack_icmp_timeout

-rw-r--r-- 1 root root 0 May 10 15:53 nf_conntrack_log_invalid

-rw-r--r-- 1 root root 0 May 10 15:53 nf_conntrack_max

-rw-r--r-- 1 root root 0 May 10 15:53 nf_conntrack_tcp_be_liberal

-rw-r--r-- 1 root root 0 May 10 15:53 nf_conntrack_tcp_loose

-rw-r--r-- 1 root root 0 May 10 15:53 nf_conntrack_tcp_max_retrans

-rw-r--r-- 1 root root 0 May 10 15:53 nf_conntrack_tcp_timeout_close

-rw-r--r-- 1 root root 0 May 10 15:53 nf_conntrack_tcp_timeout_close_wait

-rw-r--r-- 1 root root 0 May 10 15:53 nf_conntrack_tcp_timeout_established

-rw-r--r-- 1 root root 0 May 10 15:53 nf_conntrack_tcp_timeout_fin_wait

-rw-r--r-- 1 root root 0 May 10 15:53 nf_conntrack_tcp_timeout_last_ack

-rw-r--r-- 1 root root 0 May 10 15:53 nf_conntrack_tcp_timeout_max_retrans

-rw-r--r-- 1 root root 0 May 10 15:53 nf_conntrack_tcp_timeout_syn_recv

-rw-r--r-- 1 root root 0 May 10 15:53 nf_conntrack_tcp_timeout_syn_sent

-rw-r--r-- 1 root root 0 May 10 15:53 nf_conntrack_tcp_timeout_time_wait

-rw-r--r-- 1 root root 0 May 10 15:53 nf_conntrack_tcp_timeout_unacknowledged

-rw-r--r-- 1 root root 0 May 10 15:53 nf_conntrack_udp_timeout

-rw-r--r-- 1 root root 0 May 10 15:53 nf_conntrack_udp_timeout_stream

The code is as follows:

[root@Firewall core] # sysctl-a | grep net.core | sort

Net.core.dev_weight = 64

Net.core.message_burst = 10

Net.core.message_cost = 5

Net.core.netdev_budget = 300

Net.core.netdev_max_backlog = 1000

Net.core.optmem_max = 10240

Net.core.rmem_default = 111616

Net.core.rmem_max = 131071

Net.core.somaxconn = 8192

Net.core.warnings = 1

Net.core.wmem_default = 111616

Net.core.wmem_max = 131071

Net.core.xfrm_acq_expires = 30

Net.core.xfrm_aevent_etime = 10

Net.core.xfrm_aevent_rseqth = 2

Net.core.xfrm_larval_drop = 1

The code is as follows:

[root@Firewall core] # ll

Total 0

-rw-r--r-- 1 root root 0 May 10 15:53 dev_weight

-rw-r--r-- 1 root root 0 May 10 15:53 message_burst

-rw-r--r-- 1 root root 0 May 10 15:53 message_cost

-rw-r--r-- 1 root root 0 May 10 15:53 netdev_budget

-rw-r--r-- 1 root root 0 May 10 15:53 netdev_max_backlog

-rw-r--r-- 1 root root 0 May 10 15:53 optmem_max

-rw-r--r-- 1 root root 0 May 10 15:53 rmem_default

-rw-r--r-- 1 root root 0 May 10 15:53 rmem_max

-rw-r--r-- 1 root root 0 Apr 12 14:29 somaxconn

-rw-r--r-- 1 root root 0 May 10 15:53 warnings

-rw-r--r-- 1 root root 0 May 10 15:53 wmem_default

-rw-r--r-- 1 root root 0 May 10 15:53 wmem_max

-rw-r--r-- 1 root root 0 May 10 15:53 xfrm_acq_expires

-rw-r--r-- 1 root root 0 May 10 15:53 xfrm_aevent_etime

-rw-r--r-- 1 root root 0 May 10 15:53 xfrm_aevent_rseqth

-rw-r--r-- 1 root root 0 May 10 15:53 xfrm_larval_drop

This is the end of the content of "how to use the system parameter modification command sysctl in Linux". Thank you for reading. If you want to know more about the industry, you can follow the website, the editor will output more high-quality practical articles for you!

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.