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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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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27 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
37 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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20 views

Which Linux kernel versions are the most prevalent? [closed]

I am gearing up to do some scientific experiments that involve modifying the linux kernel to collect data on the internal runtime states of certain modules. We want to do the experiments over a ...
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1answer
33 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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1answer
14 views

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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16 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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18 views

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 ...
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10 views

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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84 views

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 :- $ ...
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49 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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1answer
55 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
20 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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10 views

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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1answer
40 views

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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46 views

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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15 views

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 ...
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1answer
52 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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39 views

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: ...
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46 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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20 views

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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36 views

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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2answers
31 views

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
39 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
38 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
163 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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1answer
42 views

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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50 views

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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20 views

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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29 views

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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79 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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45 views

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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1answer
54 views

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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1answer
38 views

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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35 views

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 ...
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39 views

TCP buffer sizes and ethernet bonding

(This question was originally posted on stack overflow; Andy told me that I could get faster help here, so it is re-posted here now.) I am experimenting with TCP buffer size tuning on Linux, but ...
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1answer
22 views

Clearing cached memory of uploaded file

On my system, I have a log file that is being rotated and uploaded every hour. This file is heavy on writes and only needs to be read when rotated and uploaded. The cached memory on my system is ...
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1answer
121 views

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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2answers
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patch lists for Redhat linux 5.9 -64 bit

Can any one update the lists of kernel patches released for Linux 5.9 Redhat and what is the current patch level. Thanks Mohan
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2answers
25 views

Using the output of a program as the contents of a file, dynamically

In Linux, I would like to create a file where the contents of the file are dynamically generated by the output of a program. The examples which already exist are /dev/random /dev/urandom, /dev/zero, ...
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60 views

How to increase the amount of memory used for caching on 32 bit Linux?

I have a server with 64 GiB RAM running 32 bit Debian GNU/Linux v7.9: # uname -a Linux srv1 3.2.0-4-686-pae #1 SMP Debian 3.2.68-1+deb7u5 i686 GNU/Linux # free -m total used ...
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0answers
66 views

Unusually high dentry cache usage leads to PHP performance degradation

We have lots of servers serving lots of requests with apache and php accessing remote memcacheds. But we are experiencing degradation from php side accessing memcached and obtaining lots of memcached ...
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2answers
60 views

For php webserver, what is faster, 1x 24-core server or 3x 8-core servers? [closed]

Pricing at Dell, it seems I can either get a single R430 or 3x R220's. The R220's would have 4C/8T processors, giving 24 threads. The R430 would have 2x 6C/12T processors giving again 24 threads. For ...
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1answer
218 views

Difference between net.core.rmem_max and net.ipv4.tcp_rmem

What's the difference between net.core.rmem_max and the third value of net.ipv4.tcp_rmem? Which has the higher priority for tcp connections? For below two examples, what's the max buffer for tcp ...
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95 views

Auto-Reboot on Kernel BUG (not tainted, “fixing recursive fault but reboot is needed”)

I'm running a sometimes highly loaded Debian 7 VM with the latest 3.2.x kernel on a XenServer 6.2 host. Sometimes this VM runs into the following state: Ping is okay, All Services unreachable ...
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1answer
131 views

Centos iptables: No chain/target/match by that name [duplicate]

I had a CentOS6.7 with OpenVZ. Now, I just uninstalled OpenVZ and start using Plain CentOS6.7. Due to some difficulties for using cPanel in OpenVZ. I noticed one problem when install csf in my plain ...
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1answer
45 views

Linux OOM-killer disabling woes

I have a Linux machine with no swap, which has vm.overcommit_memory=2 and vm.overcommit_ratio=100 set. However these settings seem to have no effect. Some newly-started processes which attempt to ...
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1answer
113 views

Ubuntu 14.04 TCP established hash table entries

A bit of background I am running two servers under high traffic one with ubuntu 12.04 (linux 3.2.0-69-generic) and one with ubuntu 14.04 (linux 3.13.0-52-generic). I am now trying to secure both. ...
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40 views

Empty fstab on Debian 7 and up. Possible side effects?

When I was checking a machine set up by our sysadmin team, I encountered an completely empty fstab. In fact it was the default fstab installed by a debootstrap. # UNCONFIGURED FSTAB FOR BASE SYSTEM ...
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99 views

Hide kernel messages in plymouth

I am running Ubuntu 14.04 server for Kiosk application. The problem is when kiosk is starting , kernel shows some debug messages about stuff like USB port error and such things, and those ugly ...