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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296 views

/proc/self/mountinfo per-mount-options vs per-super-options

I am trying to check for the current status of a mounted partition, rw/ro. On Cent6 /proc/self/mountinfo has some interesting info. One of the items contained in the output for each mount point is ...
1
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1answer
347 views

bad page map bug during snapshot

I ran the following command to create a snapshot volume. But the kernel received a bug and the kvm hypervisor stopped responding. Why is the error and how to fix it? lvcreate -L20G -s -n ...
3
votes
1answer
2k views

Centos 6.5 crashing with kernel panics

I recently built a small cluster for running Solr. The cluster consists of 12 Supermicro Blades running E3-1270V2 with 32GB of ram. 11 of these servers are running fine. One of them crashes on me ...
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0answers
165 views

iptables xt_recent change in kernel without modules

is it possible to change xt_recent module parameters when it is compiled into kernel ? most of the info on internet suggest setting it by modprobe but that is not the case in my setup as I have ...
1
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2answers
110 views

/sys/kernel/debug/tracing/per_cpu shows way more cpus than I have

I have 8 logical CPUs in my linux box. (As seen from /proc/cpuinfo). When I look in /sys/kernel/debug/tracing/per_cpu it shows 32 CPUs. Why the difference? If it matters, I have hyperthreading ...
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1answer
58 views

packaging current linux kernel as a rpm

I have just built a custom kernel from source (obtained from kernel.org). I can boot from it fine on my local box. I now want to make it easy for a colleague to try this kernel out. Is there an easy ...
5
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1answer
1k views

“kernel: Cannot read proc file system: 1 - Operation not permitted” — millions of such messages each minute in kern.log on OpenVZ VPS? [closed]

I'm seeing repeated never ending such messages in kern.log on my OpenVZ ubuntu 12.04 server. Mar 2 06:23:33 localhost kernel: Cannot read proc file system: 1 - Operation not permitted. Mar 2 ...
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2answers
444 views

No advantage from SSD boot drive for 24/7 server? [closed]

Since my OS and applications are loaded into memory upon boot, isn't there no advantage from having my OS on an SSD boot drive for a server that is kept up 24/7? I know there are several assumptions ...
2
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2answers
4k views

Kernel: Uhhuh. NMI received for unknown reason 31 on CPU 3

I'm receiving this error on "Linux Debian-70-wheezy-64-minimal 3.2.0-4-amd64 #1 SMP Debian 3.2.46-1+deb7u1 x86_64": Message from syslogd@hostname at Feb 14 02:54:51 ... kernel:[81927.464687] Uhhuh. ...
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3answers
171 views

freebsd 7.2 kern.threads.max_threads_per_proc doesn't change after reboot

I have some multithread apps on my server machine based on FreeBSD 7.2, so because of this I need to increase kern.threads.max_threads_per_proc to 4000 (default value is 1500). I changed it using ...
0
votes
0answers
132 views

Java causing kernel panic

I'm running quite a lot of computations on Ubuntu 12.04 (3.8.0-35-generic), application is written in Java (Oracle 1.7.0_45-b18) on a server which has 12 AMD cores. Typically the computations uses 10 ...
2
votes
1answer
2k views

Taskset not working over a range of cores in isolcpus

To preface I'm using Debian Wheezy with kernel 3.2 on an AMD64 chipset. My machine has two Xeon E5-2690 cores. I set up the boot parameters so that all the cores on one CPU are dedicated to a single ...
0
votes
1answer
111 views

Does EC2 need Xen kernel?

I am on to creating a new AMI image for CentOS 6.4. Until now I was on CentOS 5.6. I started with the CentOS market place image, and what I noticed is that it is running a regular kernel and not xen ...
4
votes
1answer
3k views

What is creating the generated/autoconf.h?

We're trying to build a piece of software that demands the kernel source, not just the headers. So we downloaded the kernel source via the centos src rpm. However the autoconf.h is missing. We tried ...
0
votes
2answers
656 views

Server shutting down for no reason, kernel errors. Please advice [closed]

My server has being shutting down by itself for the last 3 days after a power related problem. It's a KVM virtual machine. It stays on for no longer than about 20 minutes then it turns off. Note that ...
0
votes
1answer
270 views

arpd does not send ARP requests

Sometimes a botnet (or whatever) tries to port scan pretty much all IPs in the internal network (two /21 subnets) in one second. As a result the router sends out a lot of ARP requests and some slower ...
1
vote
1answer
402 views

Why Kernel Low memory zone is less then 896 MB?

In my system Lowmem of kernel (NORMALZONE) is 597424 kb length. As far as I learn, it should be about 890 MB at max. Why this system uses ~590 MB? Is it tunable? I a asking this because, I'am facing ...
3
votes
2answers
6k views

How to remove old kernels on CentOS 6 (to free up boot partition)? [duplicate]

How does one determine which kernels to remove in order to free up some space on /boot partition. Here is a scenario (some background info). 1. Parititon info (in case it helps) # df -h Filesystem ...
1
vote
2answers
101 views

How can it be that mounting and unmounting takes hours to complete?

I am running an Ubuntu server 10.10 machine with 24 hard disks (and two OS drives). I am using a script to mount all the drives to their desired mountpoints. This works pretty fast, as expected, ...
4
votes
1answer
8k views

How to find out the reason(s) why the network interface is dropping packets?

Is there a way on Linux to get statistics about the various reasons packets were dropped? On all network interfaces (openSUSE 12.3) on several servers, ifconfig and netstat -i are reporting dropped ...
1
vote
1answer
112 views

Not seeing kernel messages in syslog

I'm trying to track down a process that kills my mysql server on my CentOS box. I have the following setting in /etc/syslog.conf: *.*;mail.none;authpriv.none;cron.none /var/log/messages I ...
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votes
1answer
348 views

Debug: Cisco VPN Router runs 100% CPU

I've turned logging on and all I am currently getting are Debug/Kernel logs. Nothing above debug. This was also during offsite hours when hardly any traffic was going on. I have also upgraded to the ...
3
votes
1answer
1k views

CentOS Tuned Equivalent For Debian

Running a few systems, a few are Debian which have been great. I have on the CentOS boxes tuned(tuned-adm) installed and setup for throughput. I searched all over Google and only found some articles ...
2
votes
2answers
2k views

Multiple NIC arp issue

I'm troubleshooting an issue on Centos 6.4. I have a few systems setting up for greenplum. Each one has two "interconnect" interfaces connecting to an isolated subnet. It is like a cluster ...
5
votes
1answer
304 views

Linux Kernel lowmem usage

I am debugging an issue where we are running out of kernel low memory and I am trying to identify who is using the kernel low memory thats contributing to the problem. Following is the meminfo ...
6
votes
1answer
2k views

Linux arp cache timeout values

I'm trying to configure sane values for the Linux kernel arp cache timeout, but I can't find a detailed explanation as to how they work anywhere. Even the kernel.org documentation doesn't give a good ...
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votes
1answer
62 views

Differences between UNIX and Linux Drivers [closed]

I've been trying to find an answer to this, been on a wild goose chase. Since UNIX and Linux have different system architectures. My question is on the differences between the drivers for the SPARC ...
0
votes
1answer
2k 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
285 views

Does the initramfs image file need to be updated whenever grub.conf is modified?

I am trying to puzzle out a linux boot configuration problem involving legacy grub (0.97), LVM2, and dracut and trying to eliminate a few red herrings. My trial and error process goes like so: ...
2
votes
2answers
792 views

Best way to upgrade FreeBSD with non generic kernel (XENHVM)

Since manually upgrading from source (cvsup) is deprecated and the recommendation is to use freebsd-update: What's the best way to upgrade (e.g. 9.1 to 9.2) while keeping a non-generic (XENHVM) ...
2
votes
1answer
608 views

Idera ServerBackup / R1soft Kernel Modules

We currently have virtual (xen) servers from a host here in the UK and back up to an Idera R1Soft / ServerBackup system in the US. One of our servers absolutely refuses to compile the kernel module. ...
0
votes
3answers
846 views

Using Proxmox Kernel on Wheezy without proxmox system

I'm going to run two servers with OpenVZ on Wheezy. Since there are sadly no OpenVZ kernels in debian anymore I want to use the Proxmox kernel instead. I'm doing all replication with scripts I have ...
0
votes
0answers
131 views

Why does firehol generate an iptables ACCEPT rule on top?

Firehol generates iptables rules from a convenient configuration file. In my /etc/firehol/firehol.conf I have the following very simple configuration to allow incoming connections on http, https and ...
2
votes
1answer
102 views

How to tell which device in /dev a kernel module added?

I have just compiled the QLogic qla2xxx FC driver on a CentOS6.4 host, and done echo 'alias scsi_hostadapter qla2xxx' >> /etc/modprobe.d/modprobe.conf cd /boot cp initramfs-$(uname -r).img ...
0
votes
1answer
274 views

Server hangs after typing reboot command

I have a Debian Wheezy installation with Xen in kernel. All is fine but ... when I type a reboot command or shutdown -r now, my server is stuck and I see only that info on screen: INFO: task ...
5
votes
2answers
723 views

Optimal kernel configuration and patches for KVM host

I have a server (single socket Nehalem w/ 24GB RAM) acting primarily as a KVM host containing a bunch of Windows Servers and a few (tickless) Linux instances. I usually compile my desktop kernels ...
3
votes
1answer
536 views

What does nf_conntrack.acct really do?

I've found the kernel parameter nf_conntrack.acct interesting, in that the kernel documentation merely says "Enable connection tracking flow accounting". I've appended this to grub and rebooted and I ...
1
vote
0answers
236 views

FreeBSD XEN kernel not booting in XenServer 6.2

I have a XenServer 6.2 host, and I am trying to get a FreeBSD-9.1-i386 guest to run in PV mode. The installation of the guest is fine, but after a reboot with the new kernel the system does not boot. ...
8
votes
2answers
555 views

Why “lsmod | wc -l” not equal “ls /sys/module | wc -l”

Why do these two commands return different results? lsmod | wc -l 100 ls /sys/module | wc -l 138
4
votes
1answer
5k views

Unexpectedly shrunk window

I run a major media upload/download site and I noticed these: Is this serious or background noise due to the big file sizes and is there any tweaks I can add to /etc/sysctl.conf to improve and ...
1
vote
1answer
391 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
682 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 ...
0
votes
1answer
539 views

What kernel module to compile for getting QOS service on Linux

We are developing on Linux system whose kernel had been compiled without QOS service years ago. Currently we want the QOS service back and plan to compile only the QOS-related kernel modules and ...
0
votes
1answer
412 views

Linux kernel option to force video card to stay on

I just installed Debian Wheezy 7.1.0 on an Intel vPro System (Intel Core i5-2520M, SuperMicro MBD-X9SCV-Q-O). Intel AMT's KVM works perfectly until Debian has completed booting and shows the login ...
2
votes
0answers
162 views

Redhat 6.4 configured to log Martian packets but is not logging ll header

I am trying to investigate the source of martian packets I have been seeing on several servers connected to the same subnet. The logging of martian packets has been enabled in /etc/sysctl.conf. ...
0
votes
1answer
124 views

Xen: what are domU kernel config requirements for live migration?

We recently added iSCSI storage to two Xen servers running a mix of Gentoo and Ubuntu 10.04 and 12.04 domUs. When trying out live migration of domU I found that I can migrate just fine the Ubuntu ones ...
0
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2answers
195 views

continous kernel EIP errors

I am getting the following error time to time. Process is different at each time. What do you think about the error? What do you suggest? Kernel is Linux version 3.5.3 (developer@devel) (gcc ...
1
vote
1answer
171 views

Slackware 10.1 hangs at boot with kernel 3.x

In Slackware 10.1, what happens between rc.S and rc.M during boot? Trying to boot kernel 3.x (tried 3.4 and 3.10) on this box and it hangs right after rc.S finishes execution. 2.6 kernels boot up just ...
0
votes
1answer
52 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 ...
0
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2answers
452 views

Moving a process to and from swap [closed]

I've got serveral processes (game servers) on my linux server that use up 50MB of RAM. They are not constantly being used, and I'd like to be able to run more instances than my RAM capacity allows. I ...