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1
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2answers
87 views

net.ipv4.ip_forward reverting to 0 even though set in /etc/sysctl.conf

I set net.ipv4.ip_forward = 1 in /etc/sysctl.conf and ran sysctl -p which caused it to set to 1 as expected in the output of sysctl -a, but sometime between last night and now something set it back to ...
1
vote
1answer
73 views

cannot read key “net.ipv6.conf.all.stable_secret” in sysctl?

I am running kernel version as followings on an Arch Linux computer: [root@router ~ ]$ uname -a Linux router 4.2.5-1-ARCH #1 SMP PREEMPT Tue Oct 27 08:13:28 CET 2015 and I noticed that every time ...
3
votes
1answer
48 views

How to limit port range in Ubuntu 14.04?

I want to limit source port range in my ubuntu machine upto 20000 , that means no Application should be able to use port higher than that.I have this command in mind iptables -A OUTPUT -p tcp ...
0
votes
1answer
51 views

View current kernel parameters?

I saw in my syslog kernel.perf_event_max_sample_rate get changed. I was wondering if I could write a quick script to log this variable every few minutes. Currently it is: sysctl -a | grep ...
1
vote
0answers
53 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 ...
2
votes
1answer
119 views

Why am I unable to attach `strace` to a kworker process?

As root, I try to attach strace to a running kworker process, without success. root@rasal# whoami root root@rasal:/# cat /proc/sys/kernel/yama/ptrace_scope 0 ...
1
vote
1answer
39 views

Kill process instead of panic on hung_task

There are sysctl parameters for hung_task* that allow you to emit error messages or panic if a process is in the D state for some amount of time. Is there anyway way to have the kernel kill the ...
3
votes
1answer
143 views

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

I post this question on serverfault a few days ago but i think it's more accurate here. I know there's some topics about forcing local IP trafic of a Linux machine to go through the LAN (over the ...
2
votes
1answer
394 views

File descriptor limits in /etc/system vs /etc/sysctl.conf vs /etc/security/limits.conf on Solaris

Let me explain first what I understood. In Solaris 10, rlim_fd_max and rlim_fd_cur in /etc/system set the hard and soft limits at the system level. And /etc/security/limits.conf sets the limits for ...
2
votes
1answer
97 views

Managing settings from /sys directory in arch

I can manage /proc directory settings with sysctl and config files in /etc/sysctl.d but is there equivalent tool for the /sys directory? I want to change the I/O scheduler to bfq permanently. Should ...
7
votes
1answer
3k views

How to persist ulimit settings in OSX Yosemite?

Previous question about doing this on Mavericks is here and the answers there don't seem to work on Yosemite. I want to enable core dump generation by default upon reboot. Executing ulimit -c ...
1
vote
1answer
460 views

Permission denied on aio-max-nr file

I would like to edit the file aio-max-nr: root@node:~# echo 65536 > /proc/sys/fs/aio-max-nr -su: /proc/sys/fs/aio-max-nr: Permission denied Knowing that : root@node:~# ls -lrth ...
3
votes
1answer
255 views

Pernicious USB-stick stall problem. Reverting workaround fix?

There's an issue with Ubuntu that hasn't been fixed yet, where the PC freezes or gets really slow whenever it is copying to an USB stick (see Why is my PC freezing while I'm copying a file to a ...
1
vote
1answer
261 views

/etc/sysctl.conf Fedora {17-20}?

Since Fedora 16 or 17 there no longer file /etc/sysctl.conf. How do I setup net.ipv4.ip_forward = 1?
2
votes
1answer
3k views

What is the difference between all and default in kernel setting? [duplicate]

I want to enable reversed path filtering to prevent source ip spoofing on my server. I noticed that I have the following settings at current: net.ipv4.conf.all.rp_filter = 0 ...
1
vote
1answer
164 views

How to undo kernel settings?

While trying to read some kernel parameters, I think I have mistakenly set some instead: # sysctl --system -r ^net.*tcp * Applying /usr/lib/sysctl.d/00-system.conf ... * Applying ...
1
vote
1answer
181 views

Sysctl parameter change after every reboot

I have found that the value of net.netfilter.nf_conntrack_count variable change every time i reboot the system. Did any one have an explanation for that?
0
votes
1answer
230 views

Get a faster response for a ping

I noticed that the answer to my ping is slower in one debian machine that another. For the first one when i ping to 8.8.8.8: 64 bytes from 8.8.8.8: icmp_req=1 ttl=47 time=29.6 ms For the second ...
0
votes
1answer
130 views

Change network values from sysctl.conf

Can I change the value of those parameters (spoofprotect, syncookies, dynaddr_hack, notimestamps, nobroadcasticmpecho, ip_forward) from sysctl.conf file in systemd?
1
vote
1answer
379 views

Change sysctl parameters for all interfaces

How can i change a parameter for all interfaces in systemd ? For example: sysctl -w "net.ipv4.conf.eth0.rp_filter=0" sysctl -w "net.ipv4.conf.eth1.rp_filter=0" How can change it for all ...
1
vote
1answer
526 views

flashcache tuning

I installed flashcache version 3.1.1 and created a write-back cache. The performance is good as long as the percentage of dirty blocks is not too high. My application does heavy I/O at the ...
1
vote
1answer
2k views

What's the right way to set Linux kernel runtime parameters?

What's the prescribed way to set Linux kernel runtime parameters? I've seen sometimes that people will set these in files such as /etc/rc.local. Is this really the right way to do this?
30
votes
4answers
39k views

How to persist ulimit settings in OSX Mavericks?

Before Mavericks, one could use /etc/launchd.conf to persist ulimit settings, for example: limit maxfiles 16384 unlimited limit maxproc 16384 unlimited It no longer works in Mavericks. What is the ...
2
votes
1answer
1k views

Error: permission denied on key 'fs.file-nr'

# sysctl -w fs.file-nr=131072 error: permission denied on key 'fs.file-nr' Same issue when I edit /etc/sysctl.conf and try sysctl -p. Any reason why I cannot edit this value? I am on CentOS 6.5
34
votes
6answers
54k views

disable transparent hugepages

We are installing SAP HANA in a RAID machine. As part of the installation step, it is mentioned that, To disable the usage of transparent hugepages set the kernel settings at runtime with echo ...
18
votes
1answer
3k views

sysctl: /proc/sys/net/ipv[46]/conf/: what's the difference between “all”, “default” and “eth*”?

In sysctl, the /proc/sys/net/ipv[46]/conf/ keys have the following subkeys: all, default, and a key for each network interface. For example, on a machine with a single network interface eth0, it will ...
8
votes
2answers
3k views

/proc/sys vs /sys/modules/mod/parameter

I've been wondering for last few days how exactly does it work. We can set kernel runtimes parameters using sysctl or echo boolen 1> /proc/sys/module/exactParameter but in ...
3
votes
1answer
2k views

Benchmarking Apache using ab

I was doing some performance testing for Apache using ab. Apache in our case is only working as a load balancer balancing load between two Liferay servers. Initially, I did the testing for 1000 ...
2
votes
0answers
253 views

Unable to reduce core frequency freebsd

I'm working on a FreeBSD project where I need to maintain the temperature of the processor below a threshold value. In order to reduce the temperature I'm trying to dynamically change the frequency of ...
3
votes
2answers
10k views

Finding out the values of kernel options related to sysctl.conf and sysctl.d

On my Ubuntu machine, in /etc/sysctl.conf file, I've got reverse path filtering options commented out by default like this: #net.ipv4.conf.default.rp_filter=1 #net.ipv4.conf.all.rp_filter=1 but in ...
7
votes
2answers
3k views

Find out sysctl default values? (without rebooting)

I have modified the value of net.core.rmem_max with sysctl, and now I would like to set it back to its default value. If I reboot, net.core.rmem_max will go back to its default value (because it is ...
2
votes
1answer
5k views

sysctl parameter for correct ARP response

I have a server that has some VMs, but the VMs can't communicate properly with the server because the server has several interfaces, and it responds on the wrong one. Q: We know that there is a ...
61
votes
5answers
42k views

Can I configure my Linux system for more aggressive file system caching?

I am neither concerned about RAM usage (as I've got enough) nor about losing data in case of an accidental shut-down (as my power is backed, the system is reliable and the data are not critical). But ...
2
votes
1answer
718 views

Puppet problem with sysctl

Running CentOS 5.5 with Puppet 0.25.5 I have installed and am using the puppet-sysctl module. However the following error occurs: //linux_tuning/Sysctl::Value[net.core.rmem_default] ...
12
votes
1answer
10k views

Description of kernel.printk values

Between Debian 5 and 6, the default suggested value for kernel.printk in /etc/sysctl.conf was changed from kernel.printk = 4 4 1 7 to kernel.printk = 3 4 1 3. I understand that the first value ...