In computing, the kernel is the main component of most computer operating systems; it is a bridge between applications and the actual data processing done at the hardware level. The kernel's responsibilities include managing the system's resources (the communication between hardware and software ...

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180 views

Enable IP forwarding inside an OpenVZ container but disable it on host

Is it possible to enable IP forwarding inside an OpenVZ container but keep it disabled in host system? I understand that OpenVZ containers and host share kernels, but I can use sysctl to set ...
3
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0answers
239 views

BUG message on xenserver 6.5 - bad memory?

Several times a day I receive the following error in /var/log/messages. The server hangs and requires a reboot to respond again: Feb 1 13:44:54 xenserver-abfuqvrs kernel: [35023.166776] BUG: unable ...
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1answer
117 views

What does the tcp_fastretrans_alert error mean?

I found this error a couple of times in /var/log/messages after experiencing some odd TCP behavior: For some reason, if I connect to for example SSH for the first time in say an hour, the connection ...
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vote
1answer
64 views

Which is the physical device behind the logical /dev/___ device

From time to time I get myself dealing with this same problem: from a linux logical block device (something below /dev/), I need to find the actual hardware behind it (something probably being listed ...
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0answers
74 views

make linux kernel read swap back into memory [closed]

Occasionally, I run a script that uses the majority of the 16GB of physical memory on my workstation. The kernel then swaps out the rest to swap partitions on multiple disks. After the script is ...
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votes
3answers
5k views

VMware ESXi error upon boot “Relocating modules and starting up the kernel”

Coming back from a 4-day weekend, I noticed the A/C had been turned off for the duration of the long weekend and the heat was around 80-82 degrees. The HP ProLiant DL185G5 was running but the system ...
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vote
1answer
88 views

Influence of kernel code execution to Load average in top?

I'm trying to tests the amount of CPU that iptables use for NAT. Perhaps it will be more accurate to say "the amount of CPU that the netfilter kernel module" uses. The approach i took was to try and ...
3
votes
1answer
186 views

How to keep specific old kernels around after a yum update

I know that in CentOS 6.x, you can put the following line in /etc/yum.conf which tells yum to keep the last N kernels (by default this is set to five): installonly_limit=5 However, there are cases ...
22
votes
2answers
9k views

Does the “bs” option in “dd” really improve the speed?

Every now and then, I'm told that to increase the speed of a "dd" I should carefully choose a proper "block size". Even here, on ServerFault, someone else wrote that "...the optimum block size is ...
1
vote
1answer
42 views

Kernel dependency error on Ubuntu 12 server

I was doing my quarterly updates of an Ubuntu 12 server. After an apt-get update succeeded I'm getting this error running apt-get anything. Depends: linux-image-server (= 3.2.0.72.86) but it is not ...
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0answers
39 views

How does a kernel patch propagate into distribution updates?

I have been affected by, and helped to debug, a kernel bug. A patch has been created by the maintainer of the module, and submitted. I am interested to know how the patch propagates through to binary ...
4
votes
3answers
249 views

Modifying kernel cmdline in Ubuntu

I have a number of systems on which I need to modify the kernel cmdline, adding a few options. At the moment I do it using the following procedure: Open /etc/default/grub Modify ...
2
votes
0answers
1k views

OpenVPN ERROR: could not insert 'tun': Unknown symbol in module, or unknown parameter (see dmesg)

I'm trying to configure OpenVPN on my Debian 7 VPN but I'm getting the following error ERROR: could not insert 'tun': Unknown symbol in module, or unknown parameter (see dmesg) I tried the ...
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vote
1answer
292 views

dspam crashes with “general protection” kernel error [closed]

I use DSpam with Postfix. Recently DSpam started to crash with the following error in syslog: Nov 16 14:10:55 home kernel: [ 133.042190] traps: dspam[1692] general protection ip:7f63a493f3b0 sp:...
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votes
1answer
123 views

General protection fault by __d_drop following SMTP attack

The SMTP port (Postfix) of my box running 3.16.5 is being hammered. The log repeats this over and over: Nov 14 09:16:25 [postfix/smtpd] lost connection after UNKNOWN from unknown[177.43.41.74] Nov 14 ...
4
votes
1answer
247 views

Solaris kernel parameter equivalence to Linux

I have set the following tcp kernel parameters in Solaris ndd -set /dev/tcp tcp_ip_abort_interval 120000 ndd -set /dev/tcp tcp_rexmit_interval_max 15000 ndd -set /dev/tcp tcp_rexmit_interval_min ...
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votes
3answers
336 views

Why I should prevent yum from update kerneI?

I was googling about yum and reading some articles when I stumbled on bunch of articles about disabling yum from update kernel packages. Now I'm wondering why I should do that. When I update system I ...
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vote
3answers
190 views

delete millions of files within a directory [duplicate]

The other day I ran bleachbit on my system. I had enabled wipe disk space option in it. It took several hours and my disk space filled up completely (100GB or so). After waiting forever, I decided to ...
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0answers
198 views

How will updating kernel affect everything else?

I'm new to Linux and I'd like to try to upgrade kernel on my little NAS, but I don't really know how it will affect installed packages and user files, and do I really need to upgrade it? Plus the ...
1
vote
1answer
589 views

Command apt-get -t wheezy-backports install linux-image-amd64

I have a server with Debian wheezy and kernel vmlinuz-3.2.0-4-amd64, hosted at OVH. I would like to upgrade the kernel. Normally at ovh, you can find some kernel already configured. but the files I ...
3
votes
1answer
411 views

Linux Network tuning to prevent tcp rcvpruned and backlogdrop?

My datanodes in my hbase cluster are triggering some tcp rcvpruned and backlog drops from time to time: It seems to be there are at least two angles to approach this at: Tune HBase/HDFS etc... so ...
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votes
1answer
2k views

dummy network interface in Linux

When i create a dummy network interface and then bring it up it show up being in UNKNOWN state: root@5b8dd2855a9c:# ip l a boom type dummy root@5b8dd2855a9c:# ip l show boom 58: boom: <BROADCAST,...
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votes
1answer
1k views

What is the unit of “mem” and “memory” in /proc/net/sockstat

What is the unit of mem and memory in /proc/net/sockstat? Bytes, KBytes, Pages? [kbrandt@ny-kbrandt01: ~] cat /proc/net/sockstat sockets: used 153 TCP: inuse 7 orphan 0 tw 0 alloc 8 mem 1 UDP: inuse ...
2
votes
1answer
427 views

CPU error messages shown in console during boot — “CPU1: Stuck ??”

I recently installed a second CPU into a server. The CPU is identical to the first and I verified that the CPU is in good working order prior to the installation. The server booted up and I installed ...
0
votes
1answer
131 views

Upgrading Linux kernel module without reboot

Is there any way to upgrade linux driver module without rebooting the system ?
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votes
3answers
9k views

CentOS 6.5 new Kernel not active after reboot

Today I was running some yum updates and wanted to verify that everything went through fine by making sure I had a new kernel. To my surprise I noticed that CentOS was still running 2.6.32-431.5.1.el6....
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vote
1answer
2k views

How to check if Ubuntu 14.04 Kernel has TPROXY

I'm using Digital Ocean's Ubuntu 14.04 image and needs the kernel to be compiled for TPROXY. Is there a way to check whether the current kernel supports TPROXY?
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2answers
516 views

CentOS 6 - Kernel 3 from CentOS 7 Repo?

i want to run kernel 3 on centos 6. I found out, that it cant get installed over yum and i would need to compile it by my own. My question: Could i use the centos 7 repo to install kernel 3.x from ...
1
vote
2answers
118 views

When a socket switch to TIME_WAIT state, why I can't see its inode number?

I'm developing a program in python that parses /proc/net/tcp informations, but unfortunately, while I was doing this, I saw a strange thing. Practically, when a socket change in TIME_WAIT state, ...
-1
votes
2answers
619 views

Can you use CGroups inside an OpenVZ Container?

just a quick question, which i have had trouble finding the answer to: The OpenVZ Authors have been contributing a large amount of code to the linux kernel, in order to get virtualization features ...
5
votes
4answers
8k views

GRUB “Some modules may be missing from core image” Error

one HDD crashed from my RAID and I added a new HDD. Now I wanted to install GRUB to the new HDD: with grub-install /dev/sdb. I get these errors: Installing for i386-pc platform. grub-install: warning:...
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0answers
183 views

Verify architecture of kernel file

Note: I am NOT interested in the currently running kernel, but on a kernel that I am going to boot and which is in a file in the filesystem. I am going to boot a new kernel. I have prepared grub.conf ...
2
votes
1answer
221 views

Kernel Compile crashing on Hyper-V due to memory issues

This is on a Hyper-V machine. I've set the min RAM to 512 and the max to 2048. The host machine has more then enough RAM. Does Linux have an issue with Dynamic RAM on Hyper-V? I can't seem to figure ...
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vote
0answers
667 views

OpenVZ - updating kernel and all containers

Last night I upgraded to the latest kernel of openvz. I rebooted the host node. It came up with the latest kernel. However, the containers are still running the old kernel. What I did on the host ...
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votes
1answer
26 views

Is there anyway to specify the version of kernel update with apt-get? Debian 7 [closed]

Is possible to select the version of Kernel I need in apt-get? Actually, I need to update it but I had lot of configurations problems with 3.2. Or the only way is compiling the kernel? Thank you
2
votes
1answer
437 views

Linux read disk cache and NFS

I am interested in the impact of the read disk cache on accessing a file through NFS. Lets say I have a file on NFS. I access it (do "cat myfile") from a linux host "A". If there's enough RAM a file ...
1
vote
2answers
3k views

grub.conf missing initrd path after kernel update

I updated a server this morning and the latest kernel panics during boot. Upon review of the grub.conf file I found the initrd path was missing. Is there a way to fix this issue? Or should I remove ...
1
vote
3answers
2k views

Error installing new OpenVZ kernel

Seem to have an error when updating the kernel on a OpenVZ server when running "yum update" im getting the below Loaded plugins: fastestmirror Loading mirror speeds from cached hostfile * base: ...
0
votes
1answer
303 views

FTP server suddenly down

Suddenly I can not use anymore my FTP server and I get via ssh the following kernel report. I'm running on Debian 7.0 with ISPconfig3 kernel:[801112.466009] nf_ct_ftp: dropping packetIN= OUT=venet0 ...
1
vote
1answer
391 views

CentOS only detecting 50% of ram on IBM Server

I have IBM server with 16 GB RAM installed. Initially it showed 16 GB with free | grep Mem | awk '{print $2}' but now it shows only 8116136 but it must show 16439208 When I do dmidecode -...
21
votes
1answer
21k views

How does vm.overcommit_memory work?

When I use the default settings: vm.overcommit_memory = 0 vm.overcommit_ratio = 50 I can read these values from /proc/meminfo file: CommitLimit: 2609604 kB Committed_AS: 1579976 kB But ...
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votes
1answer
1k views

Healthy Linux machine immediately went down

This is the last log entry in /var/log/messages and after this the machine has been stopped. How can I debug why the machine has been stopped? I am not sure but maybe the system stops comes from the ...
13
votes
2answers
6k views

Kernel stack trace to source code lines

Given a kernel stack trace as below, how do you determine the specific line of code where the issue occurred? kernel: [<ffffffff80009a14>] __link_path_walk+0x173/0xfb9 kernel: [<...
2
votes
1answer
762 views

Is it possible to configure the Linux kernel I/O scheduler for an NFS mount?

On a normal block device you can change the i/o scheduler like this: # cat /sys/block/hda/queue/scheduler noop anticipatory deadline [cfq] # echo anticipatory > /sys/block/hda/queue/scheduler # ...
5
votes
1answer
2k views

Some questions about kernel.random.* parameters

I'm trying to understand the linux kernel parameters which are under /proc/sys/kernel/random/, but I have some troubles. Could you help me figure some things out? What is the boot_id parameter used ...
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0answers
368 views

collect previous kernel logs in linux after reboot

how to collect previous kernel logs in linux after reboot and how to search the old logs? Initially when system is rebooted the logs are not captured and found rest of the log's.But there is an error ...
1
vote
2answers
9k views

Server won't boot, kernel panic - not syncing

After a reboot of a CentOS 6.2 server we are getting a kernel panic with the following error: Kernel panic - not syncing: Attempted to kill init! Panic occurred, switching back to text console ...
0
votes
1answer
251 views

Initrd and Initramfs

I have read about the differences between the two from stackoverflow. But I am still finding it difficult to understand tmpfs and the real advantages of initramfs over initrd. I find that on RedHat ...
4
votes
1answer
747 views

Linux cgroups cpuset w/ subs causes cgconfig not to start

I am having a problem trying to separate 2 groups using cpuset subsystem. This works fine, however if i go to add a subgroup to that group (in this case -- user1), cgconfig will fail to start with "...
2
votes
1answer
348 views

Ubuntu 14.04 / Apache 2.4 causes kernel fault on Amazon EC2 medium instance

Got a disturbing crash while performing 'apachectl stop'. General system: $ uname -a Linux www.example.com 3.13.0-24-generic #47-Ubuntu SMP Fri May 2 23:30:00 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux ...