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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7
votes
2answers
694 views

/dev/shm & /proc hardening

I've seen mention of securing /dev/shm and /proc and I was wondering how you do that and what it consists of doing? I assume this involves /etc/sysctl.conf editing of some kind right. Like these? ...
4
votes
3answers
102 views

How to determine if a Debian upgrade updated the kernel

Let's say I have just done an aptitude safe-upgrade on a Debian system, but I was not paying attention so I did not notice if the kernel was updated or not. How can I now determine if there was a ...
2
votes
2answers
2k views

How to differentiate intentional reboot and power failure from logs

One of my centos host rebooted recently unfortunately no monitoring was implemented . How can i find out what caused it to reboot. i only have ssh access to it. How can determine if the cause is due ...
-1
votes
2answers
994 views

Why does Centos 6 have an older kernel than Ubuntu 12.04 [closed]

Hi can some one help me in understanding this. On Centos 6.2 its showing kernel as 2.6.32-220.el6.x86_64 whereas on Ubuntu 12.04 its showing as 3.2.0-23-generic. 3.0 kernel is one of the latest ...
2
votes
2answers
1k views

Xserve 10.6.8: Why do `net.inet.ip.forwarding` & `net.inet.ip.fw.enable` kernel sysctl settings stay enabled even disabling?

Very bizarre situation. I have inherited a few Xservers from a previous admin that I have been charged with cleaning up on various levels. I am familiar with settings in Ubuntu & am very ...
1
vote
2answers
220 views

Different uname -a results

I am working on a multi-server system for a client. All of the servers are fresh installs (although two were installed a couple of months ago, five a couple of days ago). They are all supposed to be ...
0
votes
1answer
933 views

How to check a driver version in linux kernel update

How I can find an information about the driver version in linux kernel update for NIC: Current: # uname -r 2.6.32-279.2.1.el6.x86_64 - # ethtool -i eth0 driver: e1000e version: 1.9.5-k ...
-1
votes
1answer
311 views

Network kernel issue dst overflow

I am currently having a issue with my server, apperently after awhile, my network will slowdown and later stop working. It shows this: Dst overflow My kernel is 2.6.18-308.8.2.el5.028stab101.1 #1 ...
0
votes
1answer
134 views

Add generic rescue kernel on Gentoo

I have a Gentoo machine (64-bit) with software RAID on boot which was set up previously by someone who optimised the kernel for that machine. Now I want to shift the disks to a new machine (also ...
1
vote
0answers
704 views

“sched: RT throttling activated” KVM host - what does this mean?

Ubuntu 12.04 64bit - under a KVM parent. 32 cores. So we seem to be having some load issues. We have noticed this line in kern.log: "kernel: sched: RT throttling activated" What does this mean? Is the ...
0
votes
2answers
225 views

Solaris 11 nsswitch.conf messed up, need to edit it from an alternate kernel

Ok, so I was editing the name-service/switch service and messed up my nsswitch.conf, I overwrote the "passwd = files" with "passwd = filesasdf" so now I can't auth to the server when I boot that ...
0
votes
1answer
107 views

Cloning instance - Original kernel not available when creating AMI

I have a EC2 Ubuntu server on Amazon cloud and I'm trying to clone an instance "X" by creating a snapshot of the instance and creating an AMI from that snapshot. The problem is: When creating the AMI, ...
0
votes
1answer
108 views

Kernel panic - not syncing: BRKADRINT

One of the machines on the network started beeping continuously and was unresponsive locally as well over the network. We shut it down keeping power pressed. Upon reboot, the boot stopped with Kernel ...
2
votes
2answers
130 views

What is the latest valid release of kernel 2.4

I want to download the latest valid release of kernel 2.4. I look at ftp.kernel.org and here the highest release available is 2.4.31, while searching on others mirrors I found that ther is also ...
1
vote
1answer
107 views

saving loaded kernel modules

I did the following in command line: modprobe ipt_LOG modprobe ipt_multiport modprobe ipt_state modprobe ipt_limit modprobe ipt_recent modprobe ipt_owner modprobe iptable_nat modprobe tun/tap ...
0
votes
1answer
54 views

enabling modules for a kernel

I have a KVM/XEN VPS and would like to enable the following modules: ipt_LOG ipt_multiport ipt_state ipt_limit ipt_recent ipt_owner iptable_nat tun/tap iptable_nat ipt_MASQUERADE ipt_POSTROUTING PPTP ...
1
vote
3answers
204 views

Performance impact of running kdump

We are currently running into an issue on a RHEL 5.6 server. The server randomly becomes unstable, kernel wait messages are showing up in /var/log/messages, and we've now had it reboot twice. We've ...
-2
votes
1answer
390 views

linux + from where uname -r take the linux version information

when I type the uname -r command on linux: uname -r I get the following info: 2.6.18-274.7.1.el5PAE my question from which file uname -r read this info , or from where uname -r read the Data ? ...
0
votes
1answer
222 views

Linux initramfs read-only

In a Linux system consisting of a bootloader, the kernel and an initramfs (no block devices, no other root filesystem): Is it possible to make the initramfs read-only once expanded into memory?
3
votes
1answer
947 views

AppArmor - root: “You do not have enough privilege to read the profile set.”

I'm trying to use AppArmor on a remote hosted Xen server with a custom built kernel. AppArmor appears to be running, but not correctly. For example if I run the following command as root: # ...
-3
votes
2answers
865 views

random server reboots [closed]

Jan 6 22:43:27 HOSTkernel: [34400.406538] Firewall: *Port Flood* IN=eth0 OUT= MAC=00:25:90:33:2c:d4:00:12:7f:34:7d:bf:08:00 SRC=141.0.9.77 DST=SERVER IP LEN=60 TOS=0x00 PREC=0x00 TTL=59 ID=2055 DF ...
5
votes
2answers
2k views

Still getting aacraid: Host adapter abort request errors after following recommended steps

I am getting the infamous aacraid: Host adapter abort request error with my new Adaptec RAID Controller under high I/O. I have read several forums, even Adaptecs, that setting the ...
2
votes
1answer
323 views

/proc/<pid>/stat children CPU time

I've been running the following command on my linux box: watch -d -n 1 "cat /proc/19866/stat" The pid above is a pid of Nginx's master process - I would expect the following fields to be changing: ...
0
votes
1answer
940 views

PPTPd - configuration error?

an 5 01:09:12 vpn pptpd[1832]: GRE: read(fd=6,buffer=611860,len=8196) from PTY failed: status = -1 error = Input/output error, usually caused by unexpected termination of pppd, check option syntax ...
2
votes
1answer
102 views

at what level modprobe operates ? - linux

I have a machine with Ubuntu 12.04 64 bit, i have the need for blacklisting a module, i have blacklisted it in blacklist.conf but nothing happened; i have solved my problem passing ...
1
vote
2answers
632 views

Server freezes and suddenly load going very high

I'm on CentOS 5.7 and I get server freezes quite a lot and the logs show the following output: Dec 26 18:33:51 server kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this ...
3
votes
1answer
2k views

HPET missing from available clocksources on CentOS

I am having trouble using HPET on my physical machine. It is not available, even though I have enabled it in my bios, forced it in grub, and triple checked my kernel to include HPET in its ...
2
votes
2answers
2k views

Tune Linux kernel against SYN flood attack

I have read an article (not in English) on how to protect a server against SYN flood attacks by modifying some directives in sysctl.conf. That article has a sentence like: "it's possible to recompile ...
3
votes
1answer
382 views

overriding default scheduler for blkio requests in cgroups

I am trying to optimize a set of servers that have to reside on single machine. i.e. i can have multiple application server, a DB server and of course a samba server as well in same instance. Now I ...
1
vote
2answers
190 views

With the kernel compiled by myself, when install VMware modules, it prompts Kernel headers not found

With the kernel compiled by myself, when install VMware modules, it prompts Kernel headers not found. My kernel source code is here: /root/kernel/linux-3.7 Where is the kernel headers?
7
votes
1answer
3k views

Why OOM-killer invoked even when huge amount of RAM is free

On EC2 ebs-backed xlarge ubuntu instance, oom-killer is getting invoked. From /var/log/syslog output below, it appears that ZONE_NORMAL is running out of memory: Node 0 Normal free:11344kB ...
4
votes
4answers
1k views

Server randomly freezes

Im facing a very strange issue, my debian squeeze freezes up always at night (Berlin, time). Here is what i get from a time and after doing this a few times, it becomes frozen and must be hard-reset. ...
0
votes
1answer
3k views

end_request: I/O error, dev sda, sector xxxxxxxxx

I have a IBM server. This server contains 3 hard disk with RAID 5. It was working fine earlier. Unfortunately this machine got the following error message. After that I have rebooted the systems. ...
7
votes
4answers
24k views

In CentOS 6.x, how can I upgrade to Kernel 3.4?

I have a server with CentOS 6.2 with kernel version 2.6.32, but I need to increase my application Performance. The Kernel Version 3.4 has x32abi which can improve the performance so i want to upgrade ...
1
vote
3answers
1k views

Ext4 kernel panic

I'm getting such kernel panics: EXT4-fs error (device md2): ext4_ext_find_extent: bad header/extent in inode #97911179: invalid magic - magic 5f69, entries 28769, max 26988(0), depth 24939(0) ...
0
votes
1answer
223 views

How to log kernel panics without KVM

My server is crashing and I can't find an answer why. It all started after my datacenter upgrade RAM from 16 GB to 32 GB. I also found such logs in dmesg - they've started to show itself just before ...
1
vote
2answers
556 views

What does the FreeBSD kernel message “vnode_pager_putpages: I/O error 5” mean?

Our FreeNAS file server's /var/log/messages and dmesg logs are filling up with: Nov 28 14:50:00 chef kernel: vnode_pager_putpages: I/O error 5 Nov 28 14:50:00 chef kernel: vnode_pager_putpages: ...
-2
votes
1answer
271 views

Which will give more free RAM to linux? [closed]

Trying to avoid some issues so I've been trying to learn vm. in kernel tuning but still a little confused even after googling. The lower background_ratio is the sooner the flushes? the lower ...
0
votes
1answer
386 views

Realtek R8168 network driver 8.034.00 not compiling under CentOS 5.8 64-bit [closed]

I'm trying to compile Realtek R8168 driver 8.034.00 on CentOS 5.8 64-bit and I got this: make -C /lib/modules/2.6.18-308.16.1.el5/build SUBDIRS=/r8168-8.034.00/src clean make[1]: Wejście do ...
1
vote
1answer
167 views

EC2 kernel decision and issues with creating a new machine with my AMI

I could really use some advice. I started a new instance on EC2 using Amazon's AMI and during the deployment process I selected a Kernel ID of "Use Default". I then configured my server the way that ...
1
vote
3answers
1k views

“postgres blocked for more than 120 seconds” - is my db still consistent?

I am using an iscsi volume on an Open-E storage system for several virtual machines running on a XenServer host. Occasionally, when there is a very high disk I/O load on the virtual machines (and ...
0
votes
1answer
662 views

Issue with kernel boot [OVH SERVER]

Trying to install OpenVZ kernel on Centos 6.3, Yes my kernel is installed i can see it in the /boot folder, yes it is Rhel6 and yes it is all up to date, i checked this with yum update. My issue ...
1
vote
2answers
2k views

FreeBSD Listen Queue Overflows - can't increase max queue size

I have a decently high trafficked FreeBSD Nginx server, and I'm starting to get a large number of listen queue overflows: [root@svr ~]# netstat -sp tcp | fgrep listen 80361931 listen queue overflows ...
1
vote
2answers
863 views

Refresh /dev/sdx list

I've been messing around with my storage array (in that case 2xMD3000 SAS) and between the scans/rescans/delete/add my /dev/sdx block devices are all messed up. Some of them are non existent and using ...
3
votes
1answer
501 views

Linux Kernel IRQ Routing with irqbalance / kernel options

I'm trying to get my Xen Dom0 distributing the irqs in an smp enviroment. As far as I know there are 2 Options: Use irqbalance Configure the kernel without cpu hotplug support My System is Debian ...
1
vote
0answers
200 views

what does setting kernel.shmall too high do?

I'd like to know what the kernel does when the value of kernel.shmall works out to being larger than the total amount of available memory (main memory + swap space). Is the value ignored and the ...
1
vote
2answers
555 views

yum update kernel without removing old?

When I yum update it wants to remove the oldest of the 3 kernel I have and upgrade to a new. Is it possible to get yum not to remove old kernels?
2
votes
1answer
1k views

Scientific Linux won't boot after yum updates kernel

I just updated kernel for my Linux: [root@localhost ~]# cat /etc/redhat-release Scientific Linux release 6.1 (Carbon) [root@localhost ~]# uname -a Linux localhost.localdomain ...
1
vote
2answers
702 views

debian kernel upgrade to 2.6.32-5-amd64 but uname still shows 686

I'm try to upgrade a debian system to 2.6 64 bit kernel with the command aptitude install linux-image-2.6.32-5-amd64 which works fine. The system reboots, /vmlinuz -> boot/vmlinuz-2.6.32-5-amd64 ...
2
votes
1answer
7k views

How to force Debian to boot new Kernel?

I'm running Debian 6, Debian GNU/Linux, with Linux 2.6.32-5-amd64 under Grub2 ( 1.98+20100804-14+squeeze1) on a remote system (no possibility to view the pre-boot messages). I compiled and installed a ...