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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“show_signal_msg: N callbacks suppressed” then pegged at 100% and machine unresponsive

This happened on an Ubuntu 14.04 64-bit DigitalOcean Droplet: Apr 22 02:17:02 localhost CRON[32514]: (root) CMD ( cd / && run-parts --report /etc/cron.hourly) Apr 22 03:16:59 localhost ...
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Server goes into kernel panic after trying to start VG [on hold]

First of all, I am not a sysadmin but I have a dedicated CentOS server hosted at OVH that I use to host one of my sites. So far so good. The server hard-disk fails currently fails to boot. This is ...
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How linux kernel make oldconfig come to know about the new symbols in the release?

We know that to build a new custom kernel on the existing old kernel we have to run 'make oldconfig' first. This command will ask us about the new configurations options added in the latest release. ...
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375 views

Debian Jessie 8 idle on fresh install always a little too high, shows rcu_sched ksoftirqd kworker causing cpu load

Are the days of 0.0 cpu load on an "idle" server gone? I have another server (centos/redhat) 32GB ram that actually runs apache/MySQL/Lamp, mono, redmine/ruby, and other junk and its still shows me 0....
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Warning :mounting fs with errors, running e2fsck is recommended

Linux server will hang and when I restart it will take around 2 hours to come up and resume normal operations. I checked the system log files and found mounting fs with errors, running e2fsck is ...
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43 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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Linux kernel 3.14: Cannot find LILO [migrated]

I'm trying to compile linux kernel 3.14 on ubuntu 14.04. Before anyone points out, I know newer stable versions of the kernel are available but I have been asked to install 3.14 itself. So, I wrote a ...
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42 views

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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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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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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42 views

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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63 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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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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What is required to activate cgroups in Linux

I have a Debian squeeze kernel (linux-image-2.6.32-5-openvz-amd64) which according to the Doku should support cgroups. When I look into the kernel configuration, it does (or is some other kernel ...
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3answers
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ext3/ext4 physical block size view

I'm using a suse 11 server with xfs and using "xfs_info /srv" command i seen this. xfs_info /srv/ meta-data=/dev/mapper/vg01-srvvol isize=256 agcount=38, agsize=1964032 blks = ...
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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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53 views

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
41 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
91 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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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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50 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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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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1answer
52 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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198 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
47 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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Linode Kernel Headers

I am trying to install the Idera (R1soft) linux agent on a Linode running Ubuntu 12.04LTS. The agent requires a driver which in turn requires the kernel headers. Linode uses custom kernels though so ...
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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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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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2answers
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Can't update linux kernel on VPS

I recently started using VPS from OVH: http://www.ovh.co.uk/vps/vps-classic.xml This is likely problem very specific to this one provider. My goal is to install and run Docker on it, for this I need ...
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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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1answer
73 views

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 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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When does an upgrade update the Ubuntu kernel?

I'm a little confused by Ubuntu/Linux kernel updates. Coming from a Windows background I sort of expect all updates to be available via the update manager, in the case of Ubuntu apt/aptitude. Yet if ...
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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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53 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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kswapd often uses 100% CPU when swap is in use

Most of the time when my computer starts to need swap, I see a massive spike in CPU usage (kswapd0 is consistently using 99%-100% CPU). According to top, the time is spent in sy (system/kernel) not wa ...
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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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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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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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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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kswap using 100% of CPU even with 100GB+ of RAM available

I'm running a Centos 7 ESXi VM with almost 300GB of RAM and 24 vCPUs. The average load is 3 and apps almost never use more than 150GB of RAM. The rest of the available memory is used by Linux for ...
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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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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 ...