The sysctl is a Unix interface used to modify variables that the kernel uses to determine behavior. There are two ways to work with sysctl: by directly reading and modifying files in /proc/sys and by using the sysctl program supplied with most distributions. The regedit interface is the closest parallel for Windows.
Questions tagged [sysctl]
174 questions
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"Not a directory" when writing kernel configurations
I am trying to toggle IPv6 on Linux systems using this function in Qt. The problem is that it fails opening the file and simply reports "Not a directory".
bool toggle_ipv6(const bool &enabled) {
const std::vector…
Chase
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How to set default HopLimit value for multicast in armLinux?
I'm trying to send packets via socket to multicast address. hopLimit by default == 1. I need hopLimit == 255 by default.
I can change hopLimit for all packets that was sent through this socket using IPV6_MULTICAST_HOPS setsockopt.
But I need…
YP_
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How to map block numbers to file names from the dmesg output resultant from vm.block_dump=1, if device is ext4?
tl;dr: I want to see/get the filenames that the reported block numbers on dmesg are part of, when vm.block_dump=1 example dmesg: bash(13515): READ block 5434824 on xvda3 (32 sectors)
When eg. sudo sysctl -w vm.block_dump=1 or eg. echo '1' | sudo…
user10239615
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Freebsd 11.1 - I added own sysctl - but it's not listed by sysctl -a command, when invoked manualy no value is shown and I cannot change it's value
Codebase is FreeBSD11.1
Code:
****
* Attempt on implementing own sycstl
****/
#include
#include
#include
#include
#include`
#include
int thats_my_stat_var=1; /*it…
KonFoozed
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2 answers
Kubernetes Kops - set sysctl flag on kubelet
We need to enable some sysctl parameters in kubernetes. This should be achievable with the below annotation in the Deployment.
annotations:
security.alpha.kubernetes.io/unsafe-sysctls: net.ipv4.ip_local_port_range="10240 65535"
When doing so the…
the_frank
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2 answers
Modify sysctl parameters inside docker container
I am running a 3 node swarm cluster and trying to launch services with
docker stack deploy
Below is my compose file
services:
nginx:
image: nginx:latest
networks:
- til-prod-network
volumes:
- type: bind
source:…
Abhinav Grover
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TCP: Setting retransmits to zero
I am using a linux machine.
I want to set the number of TCP retransmits to zero. I am using below command to modify:
sudo sysctl -w net.ipv4.tcp_syn_retries=0
The above command dont work and gives me below error:
error: "Invalid argument"…
ojas
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2 answers
What does docker run on an existing docker container do?
I am trying to change the value of somaxconn in a running docker container. I am using this command:
docker run --net=container:redis --sysctl net.core.somaxconn=65535 bash
I have checked that this command changes the value of somaxconn from 128 to…
Arpan Gupta
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Ephymeral ports range and tw buckets
Should value of net.ipv4.tcp_max_tw_buckets be lower than the range set with net.ipv4.ip_local_port_range?
And if no, why they doesn't conflicts?
Thanks
reisub83
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host_statistics64 become blocking under iOS 11
I used the code in Watching memory usage in iOS to get free memoty for years. But something went wrong since iOS 11 was born. The host_statistics64 will be blocked for 0 to 3 seconds if it is called from two threads simultaneously.
It won't be…
Dar Hoo
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1 answer
Why no error when setting socket send/receive buffer size higher than sysctl max?
Why no error when setting socket send/receive buffer size higher than sysctl max (as I have demonstrated below)? is no error the "expected behavior"?
My sysctl values for socket rmem_max and wmem_max are both set to 212992:
net.core.rmem_default =…
Trevor Boyd Smith
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2 answers
How to increase the open files user limit in boxfuse?
I'm receiving a "TooManyOpenFiles" exception. I already added a custom src/main/resources/sysctl.conf:
fs.file-max = 64000
But UnixOperatingSystemMXBean#getMaxFileDescriptorCount() returns still 4096
I guess I'd also have to set the user limit - is…
Jan
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Cygwin error that sysctl cannot be found in directory /usr/local/bin
Running tuning-primer.sh on Cygwin results in the error:
sysctl not in directory /usr/local/bin or Error: Needed command "sysctl" not found in PATH!
I have added sysctl code that I found on this url
and created files sysctl.c, sysctl.h using…
TEHSEEN
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/etc/sysctl.conf shmall shmmax calculation Oracle DB
I have a question about what COULD be the possible impact to a system, if we have the following kernel shmmax and shmall kernel settings:
# Controls the maximum shared segment size, in bytes
kernel.shmmax = 135456844800
# Controls the maximum number…
Delgado
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1 answer
Linux: programmatically get system shutdown time?
I am getting Linux uptime from file /proc/uptime. From where to get last shutdown time of machine. how to read it from wtmp file in "c". I don't want parse output of last -x command. can i get using sysctl?
Ravi Bhushan
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