Questions tagged [sysctl]
For questions pertaining to sysctl, a utility used to read and modify, at runtime, the attributes of the system kernel such as its version number, maximum limits, and security settings. Use this tag for questions about sysctl itself or questions about issues arising from using the sysctl command-line utility.
160 questions
2
votes
1
answer
80
views
OpenBSD process maps
I am using OpenBSD 7.7.
So I know that procfs is not mounted on /proc, and I need to use sysctl to fetch process maps. But this fails as I am not running as a root user. The secure level is set to 1 ...
0
votes
0
answers
151
views
In my Linux yocto-base distribution is not istalled the file sysctl.conf by the procps recipe
On my Linux Yocto-base distribution I don't find any sysctl.conf file. The proof of this is the execution of the command:
> find / -name "sysctl.conf"
which has an output empty.
On my ...
- 690
1
vote
0
answers
119
views
Using overcommit_memory = 2 crashes a Postgres container
I have a device that has Debian 11 installed, on which Docker is running.
On boot, it starts the Docker Daemon and the nine containers.
Eight of them are executing a C# program and the last one is a ...
- 111
0
votes
1
answer
440
views
What other subsystems are responsible for enabling IPv6 in when it has been disabled in sysctl.conf, and how can I track which one is enabling it?
Although I have disabled IPv6 in sysctl.conf (Debian 11), connecting my main switch to an IPv6 enabled router results in IPv6 addresses being allocated on Debian interfaces and I can ping and SSH to ...
- 7,919
0
votes
0
answers
844
views
OOM invoked regularly by PHP-FPM
I'm using EC2 instance t4g.micro which is arm64, with 1gb ram of the latest ubuntu.
I'm using nginx with PHP-FPM for upload and convert pictures using latest image.intervention with GD.
My PHP_FPM ...
0
votes
1
answer
223
views
systemctl --type=service and systemctl list-unit-files do not show all services
I have wireguard installed on a Manjaro host, and Debian Server host
The following commands show wireguard in the results on Manjaro, but nothing on the Debian server, yet the wireguard is definitely ...
- 23
0
votes
1
answer
159
views
Difference between sysctl options to set system parameters
I see on the web two different commands to load sysctl custom parameters:
sysctl --system
sysctl -p
Is there any difference between the two commands? I know the second one I posted can take the path ...
- 103
0
votes
1
answer
247
views
What if kernel parameter conflicted in grub and sysctl?
For example, if I set oops=panic in grub command and I also set kernel.panic_on_oops=0 in sysctl config? ex: in /etc/sysctl.d/
What would happen?
Are these two parameters mapping to the same function/...
- 975
2
votes
0
answers
467
views
How to change the permission of /dev/hugepages?
I have an app that open() a file under /dev/hugepages to allocate a huge page.
For now, it requires root.
How can I change the permissions?
It's automatically mounted by F38 with:
#/usr/lib/systemd/...
- 741
-1
votes
1
answer
758
views
kernel parameters + what is the right way to refresh the kernel parameter from custom.conf after reboot
we set the following kernel parameters in file 99-custom.conf
more /etc/sysctl.d/99-custom.conf
net.ipv4.tcp_low_latency = 1
net.ipv4.tcp_adv_win_scale = 1
net.ipv4.tcp_max_syn_backlog = 30000
net....
- 14k
2
votes
1
answer
4k
views
Why does setting the vm.watermark_scale_factor property increase ram consumption?
When I configure the vm.watermark_scale_factor property in /etc/sysctl.conf which is the property in charge of indicating to the kernel when the kswapd daemon starts to activate for paging from ram to ...
2
votes
1
answer
580
views
strange issue, worst network speed and worst ping latency on linux
I cannot explain this, I will start by listing these speed test results
this one is the linux host running mxlinux latest version
this one is the windows 10 running inside vmware on the same computer
...
- 131
0
votes
1
answer
278
views
Difference between fstab commit and sysctl for writing back dirty data to disk
For reducing the number of disk writes, what is the difference between using fstab to change the disk commit frequency and using sysctl for controlling when dirty data is written back to disk?
26
votes
2
answers
11k
views
kernel 5.10.119 caused the values of /proc/sys/kernel/random/entropy_avail and poolsize to be 256
After update to kernel 5.10.119, /proc/sys/kernel/random/entropy_avail became stuck to 256 and does not change when moving the mouse. It used to be greater than 3000.
# cat /proc/sys/kernel/random/...
- 263
4
votes
1
answer
556
views
Does writing a newline character into a sysctl (/proc/sys) file have any effect?
Today I ran into some code that's writing a newline character explicitly into a sysctl file. See moby/docker source code. My first thought is that the author has diligently copied the shell's ...
- 21k
2
votes
2
answers
1k
views
Linux Page Cache Performance versus memcpy
I am benchmarking the write performance in the case that Linux writes the data to the page cache without throttling the process or syncing the data to the disk. The simple experiment I am doing looks ...
- 53
0
votes
0
answers
1k
views
Can't set fs.nr_open limit via sysctl
I'm trying to set fs.nr_open via sysctl (for learning purpose) to different value, other than default 1048576
These are sysctl settings after system was booted:
vud@ubuntu:~$ sudo sysctl -a | grep -E '...
- 1
1
vote
0
answers
196
views
Setting TCP window size on older kernel
I have this:
Linux 3.10.0 #1 SMP Thu Apr 22 16:18:59 MSK 2021 x86_64 x86_64 x86_64 GNU/Linux
Trying to set this in sysctl.conf
net.core.wmem_max = 12874368
net.ipv4.tcp_rmem = 4096 42380 12874368
net....
- 111
1
vote
1
answer
421
views
Disabling IPv6 leads to black screen on reboot
I tried disabling IPv6 using /etc/sysctl.conf and after a reboot I cannot get into any of the two DE that I have installed (I am using Pop! OS 20.04). Tried both Pop Desktop and KDE Plasma. The SSDM ...
- 13
0
votes
0
answers
369
views
Limit of connections between unix sockets and tcp/ip
I have a server with the following sysctl settings:
net.ipv4.ip_local_port_range = 1024 65535
net.core.netdev_max_backlog = 65535
net.ipv4.tcp_max_syn_backlog = 50000
net.ipv4.tcp_max_tw_buckets = ...
- 1,396
1
vote
1
answer
151
views
what is the meaning of backslash in /etc/security/limits.conf
/etc/security/limits.conf looks like this
#<domain> <type> <item> <value>
#
#* soft core 0
#* hard rss ...
- 14k
2
votes
1
answer
519
views
Where to get offline documentation/descriptions of individual sysctl kernel tunable parameters?
The NOTES section of $ man 5 sysctl.conf states: The description of individual parameters can be found in the kernel documentation.
But is there a way for me to find this kernel documentation offline? ...
- 145
3
votes
2
answers
1k
views
sysctl -p failed on /proc/sys/pcie_aspm
when we run the sysctl -p on our rhel 7.2 server1 we get
sysctl -p
fs.file-max = 500000
vm.swappiness = 10
vm.vfs_cache_pressure = 50
sysctl: cannot stat /proc/sys/pcie_aspm: No such file or directory
...
- 14k
1
vote
1
answer
272
views
sysctl disable_ipv6 value gets modified during bootup. How to find out who is modifying it
In /etc/sysctl.conf I have setting net.ipv6.conf.eth0.disable_ipv6=1.
I can see after during init.d calling sysctl the value is set. Confirmed by reading sysctl net.ipv6.conf.eth0.disable_ipv6 to a ...
- 11
0
votes
2
answers
3k
views
Is there any long-term side effect of setting vm.dirty_ratio to 0?
When I used to copy a data over a thumb-drive, even if the writing speed can't exceed 2 MiB/s to the thumb-drive, Linux first copies 600 MB data to it in one second - it just writes to the RAM as ...
- 2,169