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.

learn more… | top users | synonyms

1
vote
1answer
2k views

Linux Kernel complaining about TSC when selected clock source is Hyper V

We are running RHEL 6 boxes on HyperV with Windows Server 2012. On a few on our RHEL boxes, I am seeing this error in /var/log/messages kernel: Clocksource tsc unstable (delta = -62519781 ns). ...
0
votes
1answer
363 views

Linux Cannot change tx-checksumming

On a Linux 3.2 kernel: Linux 3.2.0-4-686-pae #1 SMP Debian 3.2.46-1+deb7u1 i686 GNU/Linux on VmWare, i get checksum errors on ipv6 tcp packets. So I can ping6, but not connect by ipv6 to ssh, smtp, ...
0
votes
1answer
111 views

Make a bridge with two ports behave like a veth pair

I have a linux bridge with two ports, namely p0 and p1, and I would like to modify the bridge behavior so that every frame showing up in one port is relayed to the other port and viceversa, i.e. the ...
0
votes
1answer
390 views

LVM RAID 1 for root

I have LVM RAID 1 (not mdadm RAID 1, but exactly LVM2 RAID 1) for my root partition. I would like to make my system boot without either of the HDDs where the underlying PVs of the root LVM partition ...
1
vote
2answers
55 views

find out which memory pages are owned by kernel

I can obtain a wonderful memory map of all processes with the Linux command pmap $(ps -A | awk '{print $1}'|grep -v PID) | sort | grep \^0 It looks like ... 00007fd6dbf45000 4K rw--- ...
1
vote
0answers
105 views

ext3 option on error doesn't work

I have a redhat server 5.8 with ext3 on top of lvm, i noticed ext3 has setting "Errors behavior: Continue" in the fs super block, from the man page of mount command i readed this ...
4
votes
2answers
570 views

Linux: echo 3 > /proc/sys/vm/drop_caches takes hours to complete

I have a Thecus N8900 NAS, which is a Linux based file server, providing files via NFS to six clients. For some reason that Thecus support has yet to explain, it runs a script that checks ...
-1
votes
1answer
232 views

esxi 5 VMKernel and linux driver compatability mode [closed]

Many peoples around the web say, the esxi 5 kernel isn't based on linux kernel, but in the same times they say "ESX(i) includes a Linux driver compatability mode (drivers still have to be compiled ...
0
votes
1answer
384 views

12.04 Migration Process time delay

We have an issue in our server that is the migration process in taking time and also the load in the server is getting high due to that. No LSB modules are available. Distributor ID: Ubuntu ...
10
votes
2answers
368 views

Linux kernel detecting wrong processor frequency

After a cold boot of a 6.0.8 Debian server (HP ProLiant), ntpd played havoc with system time: offset and jitter with respect to the usual and reliable reference time servers growing without limit. ...
2
votes
1answer
65 views

Linux Kernel setup: is it good idea to enable everything in Cryptographic API?

There are several implementations for some algorithms, which use CPU instructions which may or may not be available on current system. Is it good idea to just enable (in kernel, not as modules) all of ...
0
votes
1answer
297 views

What are Linux shared memory 'segments' vs. 'pages'?

The Linux kernel docs say: shmall: This parameter sets the total amount of shared memory pages that can be used system wide. Hence, SHMALL should always be at least ...
3
votes
1answer
82 views

Linux kernel thread dependency graph?

I'm trying to benchmark a system with a software RAID-10 volume, backed by Fusion IO cards. Is it possible to display a Linux kernel thread dependency graph? I would like to know how all the ...
3
votes
1answer
73 views

How to force logging all terminal actions on Ubuntu 12.04 server?

I believe my server has just got compromised interactively. As this server will go to thrash anyway, I wonder if I can get a better insight of what the villain is doing by forcing logging of all ...
2
votes
0answers
360 views

Should I set rto_min for a route inside data center?

We have a few dedicated server rented in a data center with debian 7, kernel 3.2. We use one of those servers as a database server. The network between our application server and database server is ...
4
votes
1answer
680 views

linux initcwnd and initrwnd via /etc/sysctl.conf

Folks, As we know, the 3.x kernels have higher TCP default connection values, such as initcwnd and initrwnd. For 2.x friends, is there a way to set these in /etc/sysctl.conf instead of the ip route ...
1
vote
1answer
269 views

What is the purpose of /proc/config.gz

Please what is the purpose of the /proc/config.gz file in my Linux server filesystem? Is it some backup file, or it is an updated file by the Linux system? Can I change it?
1
vote
3answers
480 views

High CPU usage in random IP/Port UDP DDoS

I have been getting these UDP floods with random IPs and ports. randomip:randomport -> myip:randomport 0 byte payload For some reason it is using a lot of CPU. Here is the results of perf top -e ...
-1
votes
2answers
683 views

Can't resolve issue: iptables: No chain/target/match by that name

So I am trying to setup shorewall firewall on my linux vps. The vps is running ubuntu 12.10. When I type $ shorewall check I get this error. iptables: No chain/target/match by that name. ERROR: ...
1
vote
2answers
807 views

/var/log/messages showing lots of CE Err=0x2000 even on unused banks (slots)

I recently had to upgrade an old server (HP ML350G5) with used FBDIMM DDR2 RAM (could not get new ones where I live). After rebooting /var/log/messages has been plagued with CE Err=0x2000 errors but ...
1
vote
1answer
76 views

Fixed TCP payload Size [closed]

I have an aplication that need to have a fixed (516 byes) payload size in the TCP packet. The application itself can't be modified to adjust it settings, therefore i need to tune the TCP Buffer Size ...
7
votes
5answers
895 views

MySQL 5.5 degraded performance in linux kernel 3.2 compared to 2.6

Our database servers (mainly based on the Debian stable packages (=currently Wheezy) seem to have about 4 times more load for the same workload in kernel 3.2.0-4-amd64 then in it's previous ...
1
vote
0answers
162 views

Capturing on loopback device on Ubuntu LTS: 15 Mbit of traffic and “x dropped packets”

I am trying to capture about 15 Mbit of traffic on the loopback device on Ubuntu LTS using tcpdump, and I am seeing dropped packets. The CPU is a freaking i7, and i have yet to see CPU usage go above ...
0
votes
1answer
50 views

forcing linux kernel 3 to recognize cdrom as hdX

I have a problem with older version of anaconda linux installer. I have upgraded kernel in my distro, however, when this anaconda boot with this 3.4.52 kernel, can NOT find cdrom. As far as I ...
5
votes
2answers
340 views

Linux (non-transparent) per-process hugepage accounting

I've recently converted some java apps to run with linux manually-configured hugepages, as desribed here. I point out "manually-configured" because they are not transparent hugepages, which gave us ...
2
votes
1answer
416 views

Kernel panic - not syncing: VFS: Unable to mount root

I uploaded a centos 6.2 VMDK to s3 and then converted it to volume using ec2 import volume. Then i took the snapshot of the volume and deleted it.Now I am trying to create a instance from the snapshot ...
0
votes
1answer
594 views

What is required to activate cgroups in Linux

I have a Debian squeeze kernel (linux-image-2.6.32-5-openvz-amd64) which according to the Doku should support cgroups. When I look into the kernel configuration, it does (or is some other kernel ...
1
vote
1answer
488 views

please explain my fio results - is O_SYNC|O_DIRECT misbehaving on linux?

I'm going mad over figuring out what the problem could be with one of our storage boxes. With a simple fio script I'm testing random writes using bs=1M and direct=1. The SSD is a Samsung 840pro ...
0
votes
1answer
58 views

Debian squeeze kernel update under Security Updates

Can someone explain what squeeze1 and squeeze3 designate at the end of a kernel name? For instance 2.6.32-48squeeze3 is showing up under Security Updates in Aptitude.
1
vote
0answers
152 views

linux kernel configuration to filter multicast traffic based on interface

I have two virtual interfaces (eth0.2, eth0.3) in my PC. I am sending multicast data from eth0.2 to eth0.2. Multicast data is received in eth0.2 but also received in eth0.3, the other virtual ...
-2
votes
1answer
350 views

How to enable CONFIG_PREEMPT option in Linux kernel? [closed]

I am a new bee in Linux kernel programming, trying to work with an old kernel Linux 2.6.32 on x86_64. I want to enable the CONFIG_PREEMPT option in it but can not find information about how can I do ...
2
votes
0answers
53 views

Sun Fire V40z, big gap between memory reported by dmidecode and what the Linux kernel sees

I'm looking after a V40z (a loaner), running RHEL 4.8 (no, I can't update it, it's a loaner) that according to dmidecode has 8 DIMMs of 2048M each, which makes for 16GB RAM as far as I'm concerned. ...
0
votes
1answer
146 views

Linux not freeing the file buffer when we execute rm or > (redirection) operator

I have one router which has embedded-linux with kernel version 2.4.22 running on it. I know its very old version but i have to deal with it. Please take a look at the free command output when i run it ...
1
vote
1answer
870 views

RHEL 6.0 upgrading kernel from 2.6.32-71.el6.x86_64 to 2.6.32-358.2.1.el6.x86_64

[root@localhost ~]# rpm -ivh kernel-2.6.32-358.2.1.el6.x86_64.rpm error: Failed dependencies: bfa-firmware < 3.0.3.1 conflicts with kernel-2.6.32-358.2.1.el6.x86_64 [root@localhost ~]# rpm ...
2
votes
2answers
2k views

Kernel 3.8, Apache2 with WSGI : INFO: task apache2 blocked for more than 120 seconds

We have upgraded our Kernel from 2.6.32 to 3.8.7 on a Debian system. We have a sharing with NFS to get the data for Apache2. And Nginx serves only static files as a proxy. Since we have installed the ...
32
votes
5answers
2k views

Intentionally cause an I/O error in Linux?

Is there anyway, with Linux, to purposely cause a block device to report an I/O error, or possibly simulate one for testing purposes?
-1
votes
1answer
105 views

How to check/set linux’s “security level”? [closed]

I got recommended here to check the kernel's security level—how can I print it out on a linux machine? (SLES?) If it’s set too low, how can I increase it? If I set it too high, can I ever set it ...
0
votes
1answer
701 views

Linux KVM: Troubleshooting dropped packets on a Windows Guest

virsh 0.9.10 Enterprise Linux 6.3 I have a Windows 7 guest running on the KVM host and am frequently seeing 25% loss when pinging other boxes on the same subnet. The first ping request times out, and ...
-1
votes
1answer
336 views

understanding ip route show command on linux [closed]

I have a Windows 7 PC as host.The network details of my Windows PC are as follows. IP ADDRESS - 192.168.1.70 DEFAULT GATEWAY - 192.168.1.254 I have installed Virtual Box ...
0
votes
1answer
248 views

Issues with Xen Kernel and Debian

My Xen installation has gone weird on me and I am trying to get back to normal. I overflowed the base partition and in my haste to delete unused files I think I deleted something important, so now ...
0
votes
2answers
627 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 ...
3
votes
1answer
1k views

Cannot find network subsystem in cgroup on Ubuntu 12.04 LTS

I'm trying to use cgroups to limit a process's network bandwidth, as described in this answer. However, I am unable to find the "files" they refer to. I am using Ubuntu 12.04 LTS with cgroup-bin ...
2
votes
0answers
465 views

netmap issue with wheezy linux kernel 3.2.0.4 and Intel Corporation 82599EB 10-Gigabit card

I have compiled the netmap drivers on debian wheezy with kernel 3.2.0.4 and ixgbe patched module from netmap drivers code. When I insert the modules after removing default ixgbe module I get the ...
0
votes
1answer
664 views

Centos 6.3 DRBD / OpenVZ kernel/userland issue

When I start my Centos 6.3 server's drbd service I get the following error: Starting DRBD resources: DRBD module version: 8.3.13 userland version: 8.4.2 preferably kernel and userland versions ...
0
votes
1answer
613 views

Debian Wheezy No longer booting. Freezes after setting kernel variables

My Debian (Wheezy) server has been running smoothly for a very long time with no indications of any problems. I had it running 24/7 so it was always on. The other day my power went out and when I ...
2
votes
2answers
430 views

Linux process swap usage is greater than the overall system swap usage

I have a strange problem that when I run top command it shows that some processes are using around 1.5GB of swap space but then the overall usage of the system swap is way to less to something around ...
1
vote
4answers
663 views

Linux high load with ImageMagick convert utility and server freezes (blktrack output attached)

I'm using ImageMagick to convert a JPG to TIF file, and I'm using the limit options for Imagemagick as below: /usr/bin/convert -limit memory 256 -limit map 512 subjectfile.jpg -colorspace Gray -depth ...
0
votes
1answer
372 views

CentOS server high load and server freezes

My server seems to get sudden high loads within second and when I run dmesg, following logs appear: INFO: task auditd:2185 blocked for more than 120 seconds. "echo 0 > ...
0
votes
2answers
927 views

XEN kernel shows less memory 32g

I have installed Oracle Enterprise Linux 64bit on the server with 64g of RAM. But the system detects just 32b of memory, here are the details: [root@oracle-node2 ~]# uname -a Linux ...
1
vote
1answer
239 views

Scientific Linux: soft lockup on quad opteron system

After an impressive uptime of 550 days without trouble our quad opteron system turned into a corrupted system a few days after I mounted an nfs-share from a FreeNAS-box. Ongoing sessions remained ...