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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rm on a directory with millions of files

Background: physical server, about two years old, 7200-RPM SATA drives connected to a 3Ware RAID card, ext3 FS mounted noatime and data=ordered, not under crazy load, kernel 2.6.18-92.1.22.el5, uptime ...
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3answers
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Turn off the Linux OOM killer by default?

The OOM killer on Linux wreaks havoc with various applications every so often, and it appears that not much is really done on the kernel development side to improve this. Would it not be better, as a ...
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votes
2answers
7k views

Linux Kernel crash mutex_lock_slowpath “blocked for more than 120 seconds”. What to do?

I have out-of-the box Debian Lenny with non-custom kernel 2.6.26-2-amd64. Brand new server that is used to 5% of it's potential, CPU and Disk-wise. Meaning it probably not crashing because of ...
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vote
4answers
691 views

ps aux as non-root doesn't show all processes

i'm using an ubuntu 10.04 server... when i run ps aux as root i see all processes when i run ps aux as nonroot i see JUST the processes of the current user after a bit of research i found the ...
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votes
3answers
4k views

Interpreting cryptic kernel “page allocation failure” messages

I have a multi-user CentOS 6.1 database system running an application named ABC. The server is 64-bit, 8GB RAM and 6 vCPU (on VMWare ESXi 4). We get frequent dumps into the dmesg and the system logs ...
3
votes
4answers
954 views

Reloading a kernel “live” in CentOS / RHEL 6

When upgrading the kernel package on CentOS or RHEL 6, is it possible to load the new kernel without rebooting? My gut tells me it's not, but if it were, it'd be handy - especially when compiling ...
2
votes
1answer
1k views

Under what circumstances will Linux ignore the route table when choosing the MAC address for an outbound frame?

While debugging a problem with the networking configuration for a set of virtual machines running under KVM, I discovered a circumstance where the kernel in the guest VM has decided to stamp the ...
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1answer
1k 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 ...
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vote
3answers
9k views

How long does it take to fsck a volume?

We are running website which is currently serving 3-5 million page views. Our site is file sharing site and so it contains 250,000 files and few thousand symbolic links. The hard disk is a 1500GB ...
0
votes
1answer
1k views

How do i view / enable kernel logs on an ec2 instance (amazon linux)?

I've got a amazon ec2 server that i'm playing around with TCP settings in the sysctl.conf to increase the number of concurrent TCP connections it can handle, and i want to be able to view the kernel ...
18
votes
3answers
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Improving TCP performance over a gigabit network with lots of connections and high traffic of small packets

I’m trying to improve my TCP throughput over a “gigabit network with lots of connections and high traffic of small packets”. My server OS is Ubuntu 11.10 Server 64bit. There are about 50.000 (and ...
14
votes
3answers
53k views

“Possible SYN flooding” in log despite low number of SYN_RECV connections

Recently we had an apache server which was responding very slowly due to SYN flooding. The workaround for this was to enable tcp_syncookies (net.ipv4.tcp_syncookies=1 in /etc/sysctl.conf). I posted a ...
5
votes
3answers
5k views

How can I find out what is causing interrupts on Windows?

Occasionally I come across servers (Windows 2003 and 2008) with high processor % interrupt time. Is there a way to see what program or device is causing the interrupts?
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votes
3answers
4k views

Kernel Log “TCP: Treason uncloaked!”

On one linux server (Gentoo hardened), we are experiencing bursts of the following messages in dmesg from time to time: TCP: Treason uncloaked! Peer xx.xx.xxx.xxx:65039/80 shrinks window ...
12
votes
8answers
2k views

Is it important to reboot Linux after a kernel update?

I have a few production Fedora and Debian webservers that host our sites as well as user shell accounts (used for git vcs work, some screen+irssi sessions, etc). Occasionally a new kernel update will ...
5
votes
4answers
19k 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 ...
4
votes
3answers
625 views

Compiling kernel version >= 2.6.34 on CentOS 5: RAID set “ddf1_foo” was not activated?

I want to mount a Ceph FS on some CentOS 5 servers. Since the ceph-fuse failed with below errors: # ceph-fuse --no-fuse-big-writes -m 192.168.2.15:6789 /mnt/ceph/ ceph-fuse[7528]: starting ceph ...
2
votes
5answers
13k views

possible SYN flooding on port 80. Sending cookies

I recently had a server downtime. I looked everywhere and the only thing I found in my log files is: Feb 17 18:58:04 localhost kernel: possible SYN flooding on port 80. Sending cookies. Feb 17 ...
5
votes
2answers
7k views

Can I increase inode count in Linux?

Sorry for my poor English. I have a Linux MIPS router with 2.4.17 kernel. Root fs is a tmpfs and /rom is a cramfs. There is 4MB free memory and 3MB free on tmpfs. I can create a few new empty ...
4
votes
2answers
9k views

How do I upgrade the kernel in Ubuntu Server 10.04?

I'm running Ubuntu Server 10.04 LTS. When I login I see the message: 39 packages can be updated. 18 updates are security updates. The usual formula of sudo apt-get update sudo apt-get upgrade ...
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vote
1answer
1k views

Unable to mount fat drive in linux

This is sort of a continuation from How to mount a .bin image file in linux but it morphed into a different problem altogether, so I figured I'd ask a new question with the relevant info rather than ...
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votes
3answers
2k views

how do I convert a live root ext3 filesystem to ext4?

I have a root filesystem thats live and mounted and I'd like to convert it to ext4. All the howto's i've read deal with booting off a live CD but thats not an option.
2
votes
1answer
282 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 ...
2
votes
3answers
3k views

Compiling realtime kernel from RHEL 6 MRG sources on CentOS 6

I'm trying to compile kernel-rt-2.6.33.9-rt31.75.el6rt.src.rpm from RHEL6 MRG source RPMs on Centos 6 x86_64 system. It's first time I'm doing this, so I did research on how to do this properly. From ...
1
vote
1answer
101 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 ...
1
vote
2answers
1k 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 ...
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2answers
2k views

Log - Server kernel: INFO: task httpd:000000 blocked for more than 120 seconds

Almost everyday my server is crashing due to hight server load, and even restarting apache or mysql can't solve the problem. I need to reboot the server to solve, or it crash again due to the high ...
1
vote
2answers
254 views

Error: Can't alloc conntrack

What does the message in kernel.log: nf_conntrack_alloc: Can't alloc conntrack
0
votes
1answer
790 views

Why is Linux choosing the wrong source ip address

and what to do to let it choose the right one? This all happens inside an OpenVZ container: The Host is Debian/Wheezy with Redhat/OpenVZ Kernel: root@mycl2:~# uname -a Linux mycl2 ...
0
votes
2answers
1k views

Compiling linux kernel - `make install` asks for LILO. Now what?

So I am following this guide to compile my custom kernel - http://library.linode.com/linode-platform/custom-instances/pv-grub-custom-compiled-kernel#sph_compile-and-install-the-kernel So far so good, ...
0
votes
2answers
1k views

Kernel update without reboot [duplicate]

Possible Duplicate: Reloading a kernel “live” in CentOS / RHEL 6 How can i update kernel on Centos without reboot .? I found ksplice but it is not supported for Centos. ...
0
votes
1answer
724 views

Xen Kernel on Debian Squeeze making 1GB memory 'absent'

Possible Duplicate: Fresh Debian Squeeze (6) Installation - Very High Ram Usage We have a Dell Poweredge R210 server with 8GB of installed RAM. This is a fresh install of Debian Squeeze, ...