Questions tagged [sysctl]

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23 questions with no upvoted or accepted answers
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Why is my `net.ipv4.ip_forward = 1`?

I just discovered accidentally that cat /proc/sys/net/ipv4/ip_forward returns 1. I can't remember having enabled net.ipv4.ip_forward anytime ago, but since my system runs for several years now, I can'...
3
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0answers
845 views

Gratuitous ARP packet gets not send out even if “arp_notify” in sysctl is set to 1 on OpenWRT

I am running a router on OpenWRT 15.05.1 and I did notice, that it does not send out Gratuitous ARP packets on a change of the IP address, nor on a reboot, nor on change of the Ethernet link state. ...
3
votes
1answer
715 views

Force local IP traffic to go through LAN WITHOUT ip address changes

I know there's some topics about forcing local IP trafic of a Linux machine to go through the LAN (over the network where a WireShark is captuting trafic) but all solutions implies IP address ...
2
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0answers
75 views

Using a large number of nullfs mounts to create a virtual FS on FreeBSD - what are the practical limits + impacts?

I have a situation where I'm possibly going to create a virtual file system on FreeBSD, comprised entirely of nullfs mounts of selected "ordinary" dirs within my various ZFS datasets (and their ...
2
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0answers
252 views

Is there an alternative for net.ipv6.ip_nonlocal_bind on FreeBSD?

On Linux (Kernel >= 4.3) I can "claim" an entire IPv6 subnet by routing it to localhost (sf#403648), and then by setting net.ipv6.ip_nonlocal_bind=1 so that I can bind on any of these addresses. I ...
1
vote
1answer
140 views

What's the purpose of use_tempaddr=1 kernel parameter?

Reading sysctl docs, I found the following: use_tempaddr - INTEGER Preference for Privacy Extensions (RFC3041). <= 0 : disable Privacy Extensions == 1 : enable Privacy Extensions, ...
1
vote
1answer
1k views

Disable core file generation in RHEL7

I'm currently running RHEL7. I haven't been able to find a definitive explanation of how to disable core dump files. I can limit to number of core files that are produced, but I don't know how to ...
1
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0answers
284 views

Can't change kernel.printk value

I want to set kernel.printk value to 5 4 1 1 for disable logging on booting but when I try sysctl -w kernel.printk="5 4 1 1" I get error: sysctl: setting key "kernel.printk": Invalid argument ...
1
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0answers
63 views

write error for rmem_max on Angstrom

I am trying to tune the UDP receive and transmit buffer size. According to my real time application needs, I need to configure the Tx buffer as 6 bytes and Rx buffer as 22 bytes. I am running Angstrom ...
1
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0answers
125 views

sysctl IPv6 funtional defaults

ip-sysctl.txt: accept_ra_defrtr - BOOLEAN Learn default router in Router Advertisement. Functional default: enabled if accept_ra is enabled. disabled if ...
1
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0answers
453 views

linux sysctl tunable knob kernel.yama.ptrace_scope

The reference lists as values 0,1,2,3. Today I tried it on two servers : kernel 3.0.0 sysctl -w kernel.yama.ptrace_scope=3 error: "Invalid argument" setting key "kernel.yama.ptrace_scope" ...
1
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0answers
533 views

change TCP_TIMEWAIT_LEN at runtime

Linux kernel defines a timeout to destroy TIME-WAIT state of a connection in include/net/tcp.h: #define TCP_TIMEWAIT_LEN (60*HZ) Is there a way to change this parameter at runtime, via sysctl or /...
1
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0answers
733 views

Linux + kernel tuning parameters

I configured the following parametersbut after restart the values return to the previews values. How to configure them as permanent? echo 500 > /proc/sys/vm/dirty_expire_centisecs echo 3 > /...
1
vote
1answer
541 views

Why remount of /proc/sys is not global or does not persist in network namespace inside LXC

I have host running RHEL-7.2. Inside that running LXC. Inside LXC creating network namespaces. Inside the namespace changing sysctl variables was failing (as root): $ ip netns add testns $ ip netns ...
1
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0answers
285 views

Can you set Linux sysctl values at compile time

I am compiling a custom linux kernel. I want to set some sysctl values at kernel compile time. Defaults I want are different to the defaults kernel sets. Is there a way to do this? Please note I ...
1
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0answers
88 views

/etc/sysctl.conf abstraction for custom usage

Is there an abstraction model for configuration files like /etc/sysctl.conf ? I find it great for a few reasons, it's humanly readable, has nestable namespaces, hierachy of settings instead of one-...
1
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0answers
663 views

UDP buffer overrun and old datagram clearing

I am reading UDP datagrams on a linux server at 700,000 per second from HDL32 LIDAR system. Interface is ipv4. Sockets are set to SOREUSADDR. I turn on the LIDAR, start up socket program, it started ...
0
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0answers
60 views

Kernel parameter about max threads not being applied

I have manually edited /etc/sysctl.conf and added this line kernel.threads-max=70000 However despite the fact that # cat /etc/sysctl.conf | grep thread kernel.threads-max=70000 what I see is that ...
0
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1answer
42 views

oracle 11g installation on ubuntu 16.04 sysctl permission denied?

I am trying to install oracle 11g on ubuntu 16.04 after setting oracle 11g xe kernel parameters successfully # Oracle 11g XE kernel parameters fs.file-max=6815744 net.ipv4.ip_local_port_range=...
0
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1answer
119 views

Disabling all devices in /proc/acpi/wakeup permanently

In an effort to weed out an acpi problem, I need to set all the /proc/acpi/wakeup device variables to disabled. For the time being I'm doing it with acpitool and a script in /etc/rc.local ... usr/...
0
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1answer
115 views

how to turn off tcp timestamps?

I tried to turn off the tcp timestamp but it didn't work. The step i performed are the following: $ sysctl -w net.ipv4.tcp_timestamps=0 $ sysctl -p $ sysctl net.ipv4.tcp_timestamps (=> to be sure ...
0
votes
1answer
470 views

Enabling rp_filter loose (#2) mode for IPv6

does anyone have a solution to make reverse path filtering work (in loose mode) also for IPv6 and not only for IPv4? The setup I am having is a machine1 connected directly to a machine2, while ...
0
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0answers
397 views

How do I make my system only use swap when RAM is totally full?

In the past, setting vm.swappiness to 0 meant the system would only swap when RAM was totally full. $ cat /etc/sysctl.d/99-sysctl.conf kernel.sysrq = 1 vm.swappiness=0 $ sysctl vm.swappiness vm....