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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2answers
790 views

Linux server resend SYN ACK

I am troubleshooting a connection timeout problem between two Linux boxes, where it seems the ACK to SYN-ACK was lost on the server's stack. The tcpdump is done on the server side. The client got ...
0
votes
2answers
2k views

CentOS 6 Xen guest fails to boot after 'yum update'. Kernel?

I Seem to be having an issue with a Xen guest not booting after a yum update. DomU Configuration: #kernel = '/boot/solus-vmlinuz' #ramdisk = '/boot/solus-initrd.img' bootloader = ...
3
votes
1answer
165 views

firewall output flooding dmesg

I log all dropped packets using following iptables rule: -A INPUT -j LOG --log-prefix "FW_DROP: " --log-level 7 and then in rsyslog.conf, I redirect this output to a separate file, so that my ...
0
votes
1answer
197 views

Effects of IW10 (initcwnd 10 initrwnd 10) on high speed LAN based TCP/IP communications?

What does changing the number of packets sent during the initial congestion window to 10 have on LAN connections? Via: ip route change default via GATEWAY dev INTERFACE initcwnd 10 initrwnd 10 Is ...
1
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0answers
267 views

UDP socket receive buffer size change on RHEL6.3

Our system used to work on RHEL5.3 And the socket receive buffer size is 64k. And that works fine. We can get message size up to 64k on UDP socket. But after system upgrade, it is running on RHEL6.3 ...
0
votes
2answers
530 views

Why does my server boot the old debian kernel?

I got a vServer with Debian installed (important because I have no idea of how Debian was installed and/or built). Output of ~# uname -r: 2.6.26-2-xen-amd64. After execution of (first some other ...
8
votes
4answers
3k views

How can I troubleshoot high Kernel time?

I have unusually high Kernel time on my CPUs as shown in task manager. What are some ways I can troubleshoot this?
0
votes
1answer
352 views

mpt2sas1: log_info(0x31120303): Disks dropped from RAID

In my syslog I get loads of: Mar 1 11:20:07 franklin kernel: [72947.878407] Waking error handler thread Mar 1 11:20:07 franklin kernel: [72947.878415] Error handler scsi_eh_1 waking up Mar 1 ...
0
votes
2answers
294 views

Is the latest kernel mainline release stable [closed]

Looking at kernel.org the latest mainline release is 3.8. Zhe site also states the latest stable release is 3.7.9. Now looking at http://en.wikipedia.org/wiki/Linux_kernel inside the version history ...
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1answer
161 views

btrfs balance kernel bug? [closed]

After getting a little annoyed with no space left errors when deleting files I started a btrfs balance process and 2-3 times the following appeared. Is this serious for my data or can I just ignore it ...
2
votes
3answers
350 views

How to install packages with APT without user interaction?

I have a script that downloads and replaces kernel headers in Debian squeeze. function fixHeaders(){ #Replace the kernel headers from OVH with standard kernel headers... aptitude -y install ...
2
votes
1answer
2k views

Kernel Errors Present: EXT4-fs

Logwatch is giving me the following error: WARNING: Kernel Errors Present EXT4-fs (sda1): error count: 4 ...: 1 Time(s) EXT4-fs (sda1): initial error at 1350482172: e ...: 1 Time(s) EXT4-fs ...
7
votes
2answers
525 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
92 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
1k 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
885 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
779 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
168 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
402 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
178 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
113 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 ...
0
votes
0answers
540 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
199 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
95 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
86 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
100 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
79 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
0answers
50 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
151 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
282 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
156 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
815 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: # ...
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votes
2answers
457 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 ...
4
votes
2answers
1k 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
271 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
584 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
92 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
473 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
1k 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
1k 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
308 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
179 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?
3
votes
1answer
2k 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
975 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
2k 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. ...
5
votes
4answers
20k 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
803 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
191 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
390 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: ...
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votes
1answer
207 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 ...