The Linux kernel is the operating system kernel used by the Linux family of Unix-like operating systems. It is one of the most prominent examples of free and open source software.

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monitor traffic at the scale of millisecond

I have several linux servers running Ubuntu 14.04, and turned them into a Spark cluster. At this point, I want to measure the network flow between the servers, at the scale of milliseconds, in order ...
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Where is PPPoE session id Stored in linux?

How can I get Session ID of my current PPPoE session I have tried Wireshark but I did get Session ID but is there any other method like file in linux ?
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How to upgrade Linux Kernel (Linux vps180 2.6.32-37-pve #1 SMP Wed Mar 18 08:19:56 CET 2015 i686 GNU/Linux)

Good Day! Im having a difficulties in upgrading this server's kernel. Since I am new to this server management. Anyone who have idea to upgrade this type of server ? Linux vps180 2.6.32-37-pve #1 ...
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Martian sources from my public IP

These days I get some Martian packets in the kern.log: Jul 7 02:28:20 box14932 kernel: [789192.798073] IPv4: martian source XXX.XXX.XXX.XXX from 10.91.12.01, on dev eth1 Jul 7 02:28:20 box14932 ...
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CentOS 7 - software raid md devices not available with new kernel

Some background. The servers I am working on currently are hosted at OVH whom uses a custom GRS kernel with some functionality I need disabled. Although they do give the option to install the native ...
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29 views

Linux no modify time (nomtime)

Is there a way to disable the mtime of an filesystem? There is an Filesystem independend noatime Option, but no "nomtime". Also in the Filesystem specific documentation for ext4 and/or btrfs i couldn'...
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Unable to create new native thread

I am using 128 GB 16 core ec2 instance after running multiple (java) applications . I got " unable to crate new native thread" error I checked issue In /etc/sysctl.conf Kernel.core_uses_pid=1 It ...
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75 views

Change kernel of Centos OVH

I'm using a server of OVH with OS centos7. OVH has its own linux kernel: 3.14.32-xxxx-grs-ipv6-64 Now I try to configure another Centos7 kernel. I installed the other kernel(s). yum install kernel ...
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1answer
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CentOS: After Kernel Update system does not boot (/dev/md2 does not exist)

after doing a kernel-update (only via yum update) my centOS 7 (64bit) does no longer boot. I now booted into rescue-mode and tried to mount /dev/md2 - this worked fine: Any ideas what I could do ...
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60 views

How to I reconfigure grsecurity patch on Debian kernel

I installed the linux-image-4.4.0-1-grsec-amd64 on Jessie from the Debian package repo. Having issues with LXD and grsec Chroot restrictions, I went to make adjustments to /etc/sysctl.d/grsec.conf ...
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cgroup same process with different resources

I have a Jboss application server installed through source and running multiple instances(say 3) of JBoss as a same user in a single machine on different ports. Using cgroups, I'm trying to do ...
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85 views

Kernel headers not found in Cent OS 7

I was trying to install ixgbevf drivers. # dkms build -m ixgbevf -v 2.14.2 Error! echo Your kernel headers for kernel 3.13.0-74-generic cannot be found at /lib/modules/3.13.0-74-generic/build or /lib/...
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Building CentOS kernel from RPM with patches (but missing files that are in the SRPMs)

I have a hardware system that I am running CentOS 7 on. I would like to add some patches to the default CentOS kernel, since I have some custom hardware to support, but I also want to track the ...
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84 views

Configuring vxlan unicast in linux

I want to try vxlan unicast and configured following configurations in Fedora 23 VM1(enp0s8) ========= (enp0s8)VM2 ip address add 100.1.1.1/24 dev enp0s8 ifconfig enp0s8 up ip link add name vxlan42 ...
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1answer
37 views

Large percentage of identical systems hang on soft reboot

Reaching out for any other ideas after banging my head against this problem for a week. We have approximately 100 identical systems using the AAEON PICO-ITX BT01 motherboard with J1900 Celeron ...
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kernel: OUT setsockopt exception observed in syslogs

We are facing the issue of sudden reboot of the machine. There are no errors in the iLO logs. We are observing below exception repeatedly in the syslog, which I am unable understand. kernel: ###OUT ...
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26 views

Why is my scaling_max_freq stuck at 1GHz (on a Core Duo processor)

I recently setup an old Thinkpad T60 as a secondary desktop (via a docking station), but when I tried it, it was feeling sluggish and I soon figured that it was somehow stuck at 1GHz, even tho its ...
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mdadm - stuck reshape operation

I have a 3 disk RAID 5 array that I tried to add a 4th disk to. mdadm --add /dev/md6 /dev/sdb1 mdadm --grow --raid-devices=4 /dev/md6 This operation started successfully and proceeded until it hit ...
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1answer
44 views

Can I extract a private key out of Tomcat's memory?

I'm running Tomcat 6. I was messing around with my keystore in order to try to fix some certificate chain problems, and I accidentally rm'd the production version instead of the .new file I was ...
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1answer
123 views

How to use pNFS in NFSv4.1

As I know, pNFS is an extended protocol over NFSv4.1. So, I have two questions: How to use pNFS in NFSv4.1? Is there any special requirement for kernel version in server side?
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ksoftirqd/0 hit ~100% cpu usage led network lag

I run an app on CentOS6(e5-2667v2 x2 with 128GB RAM, 1000M network interface), When network load up to ~300Mbit/s, the ksoftirqd/0 process hit ~100% cpu usage, and begin loss packet. How can I do?
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185 views

Segfault in libc-2.19.so with Webmin

I recently upgraded the kernel one of my Debian 8 servers which has Webmin+Virtualmin installed on it. The server had usual Virtualmin backups setup which used to work fine before the upgrade, but ...
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Kernel Crash - kernel: BUG: unable to handle kernel paging request at 00000000ff8179b9

One of my Oracle Linux 6.5 Server running Oracle ASM/GRID experienced a kernel crash, it didn't respond i have performed a hard reboot. Server is Oracle Linux 6.5, kernel 2.6.39-400.214.3.el6uek....
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Install kernel modules during an ParaVirtual to HVM AWS instance upgrade

I am trying to create a clone of a PV AMI to an HVM one. The PV AMI is an Ubuntu 12.04 and I cannot upgrade that version. I do have a base Ubuntu 12.04 that is HVM enabled with Enhanced Networking. ...
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Logging In as a root user to a remote machine using SSH

My problem is similar to this one , I am trying to automate the portion where I can access the remote machine and run a command as super user. It works fine till it logs-in , like from here :- $ ssh-...
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53 views

How do you run a script when a kernel oops occurs?

I would like to run a custom script when a kernel oops occurs. Is this possible, and if so how?
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254 views

How to compile drivers for Centos 7 with mainline kernel 4.5.0.0-1 from @elrepo-kernel

When using CENTOS 7 with Kernel 4.5, I can not yum install kernel-headers with the same kernel version. I am stuck on 3.10, which is what Centos comes with. How can I install Kernel-headers 4.5 and ...
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2answers
53 views

system unresponsive after soft lockup

We observed frequent soft lockup issues on Ubuntu 12.04 (kernel: 3.8.0-29-generic) and found system unresponsive after that. Here are kern.log message just before soft locks occurred. Any help would ...
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How to handle this warning: The Linux source in /lib/modules/3.19.0-25-generic/build has not been configured

I am trying to install a Sangoma PRI card on a Ubuntu 14.04 LTS. During installation of the drivers, it gives me this warning, followed by other errors which are a consequence of this issue (or so I ...
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Linux Mint Stuck at “nm-dispatcher.action: Disconnected from the system bus, exiting.” when shutting down

As the title implies, whenever I try and shutdown my Linux Mint Aspire-ES1-111M 3.13.0-37-generic laptop it hangs at "nm-dispatcher.action: Disconnected from the system bus, exiting." I never get the ...
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Linux vm.vfs_cache_pressure affect page cache or not?

I want to limit page cache in linux. Some documents say increase vm.vfs_cache_pressure to control the kernel reclaim memory. I try, but not work. Linux/Documentation/sysctl/vm.txt say "Decreasing ...
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How to build configfs kernel module externally

I've used the standard make -C /usr/src/$(uname -r) M=$(pwd) modules invocation to build many out of tree modules before (ath, e1000e, etc). Despite being defined as a tristate (tristate "Userspace-...
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1answer
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Oracle invoked oom-killer even when RAM and SWAP is plenty free?

Can you please tell me what cause this Oracle process killed? Seems like plenty of RAM free, and plenty of SWAP free. There followed few other oracle processes killed. The VM has the 16G of vMem and 8 ...
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How to troubleshoot strongswan error: “unable to allocate SPIs from kernel”?

I am trying to setup an IPsec tunnel to a Juniper security gateway using a strongswan client on a Linux machine and preshared keys. This is what I get when trying to bring the connection up: root@...
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57 views

TCP sockets dying on LTE

I have about 25 audio streaming clients built on an i.mx6 arm platform, running linux version 4.3.0-rc2-00019-gbcee19f-dirty #36 SMP Tue Feb 9 15:27:51 EST 2016 armv7l I find on two specific units ...
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tcp receive buffer size min value seems not work

I tried to increase tcp min receive buffer size to 87380, so in my test it would OOM quickly with a little connections. net.ipv4.tcp_rmem = 87380 87380 6291456 net.ipv4.tcp_wmem = 87380 87380 ...
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memory usage reporting by kernel in log when task is killed due to OOM

My task inside docker container are getting killed due to OOM. Here is a log from /var/log/messsages. Feb 17 19:01:24 ip-10-0-1-85 kernel: [16211.346602] uwsgi invoked oom-killer: gfp_mask=0xd0, ...
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Why takes CLEARING swap soo long?

Why is moving from RAM to swap fast and from swap to RAM very slow? When I run program that needs more memory that is available, I see that the RAM is prety quickly "cleaned" by moving unsused (=the ...
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1answer
62 views

Unmount a rbind mount without affecting the original mount

There is another question discussing about umounting rbind mounts, but the solution has unwanted effect. Consider the following directory layout: . ├── A_dir │ └── mount_b ├── B_dir │ └── ...
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1answer
66 views

Segmentation fault on dd command

I ran this command on Ubuntu to resize the /tmp and after that there is segmentation fault coming. dd if=/dev/zero of=/dev/xvda1 bs=1024M count=2 Its our live server. Is there any way to get it ...
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1answer
416 views

How to properly permanent enable ip forwarding in Linux with systemd?

I try to enable ip forwarding (between enp0s3 and tun0 interfaces) and write net.ipv4.ip_forward = 1 in /etc/sysctl.conf. After restart I have $ cat /proc/sys/net/ipv4/ip_forward 1 But forwarding ...
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Recovery action for reserved kernel page: Failed

In a fresh install of 15.10 server, kernel 4.2.0-16-generic, I'm seeing the following entries in my kern.log file: Feb 1 11:49:30 Client-5 kernel: [ 117.847487] MCE 0x1182: reserved kernel page ...
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Xen VGA passthrough w/ XEN_PCIDEV_BACKEND kernel option

Xen's webpage ( http://wiki.xenproject.org/wiki/Xen_VGA_Passthrough ) says this is a requirement for VGA passtrough: "dom0 Linux kernel needs "XEN_PCIDEV_BACKEND" option enabled." I'm running ...
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Easy way to send local configuration to server

Pretend I have setup a server hosting for a website locally (on my Linux laptop), it all works perfectly. It has all of the files for the website, firewall has been setup, apache install etc... For ...
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How to reliably capture Linux kernel log messages in case of a system debilitating crash (BUG, panic)?

I'd like to have access to the lines/tracebacks/whatever whispered by the kernel right before dying. This has proven problematic, because all interfaces I have access to become disabled. Post-reboot, ...
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159 views

Debian Preseed: Installation process stuck at 18 % at finishing-installation

My Preseed installation of Debian is stuck at 18 % and i don't know what's wrong. Can you help me please? Here is syslog screen: Syslog Here is my preseed file: #C ontents of the preconfiguration ...
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Troubleshooting with kernel call trace and underlying root cause with XFS

How to determine the root underlying cause of an error when looking through a Linux kernel call trace, and in which order should I read the call trace? From my understanding, the call trace should ...
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Linux route unexpected mtu

i'm observing rather strange (at least for me) behaviour for few routes in my network. i use gre interfaces on top of ipsec tunnels. these gre interfaces have mtu 1400 on my entire network. normally i ...
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Memory Hotplug in Linux is supported?

Does someone know, if the underlying hardware supports memory hotplug, in Linux is supported without reboot? Especially in Centos 6.x(x86_64). Thanks
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Strange messages in my syslog on Debian

I am getting strange messages on my /var/log/syslog that aren't usual. I am running a Debian Jessie LXC Container inside of a Debian Wheezy machine. But I believe this is not the problem. An example ...