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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FreeBSD Established Connections Maxing out at 300

We've previously had issues in our environment where it seemed we were reaching FreeBSDs max connection limit. We took action demonstrated by http://nginx.org/en/docs/freebsd_tuning.html and bumped up ...
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37 views

kvm hypervisor kernel panic

My kvm hypervisor had been running with 20+ vps guests for a few months. But a few days ago it went to kernel panic. There were no abnormal operation that I found would cause the problem, except that ...
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Linux kernel module “Unknown parameter” stops module from loading. How to load module anyway?

The following is happening on a Ubuntu 10.04 system I'm working on: The kernel is shipped with e1000 driver module version 7.3.21-k5-NAPI. This version of the module is causing problems. To fix, the ...
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1answer
28 views

Error during the kernel booting

After kernel update I've got a problem with booting linux, does anyone know how to fix this problem ?? I am pretty sure that everything was OK during kernel compilation. Here is a picture with the ...
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1answer
28 views

Kernel Upgrade with grsecurity - Debian

I would like to upgrade kernel on my server from version 2.6.32 to the newest with Grsecurity. But after restarting the server there is still old version of kernel, can you tell me what I have done ...
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35 views

yum update leads kernel error

When I do 'yum update', the following error is shown. Before running the suggested command, I shall better understand, what the cause is. Any advice? --> Finished Dependency Resolution Error: ...
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1answer
83 views

RHEL6 Keeping 1 old kernel and security

I have my RHEL 5&6 servers set to keep 1 old kernel after updates, I do this in case I need to recover the system for any number of reasons. My question is related to security of the system when ...
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3answers
48 views

Yum update problems on AWS with missing requirements and duplicate sendmail

I am running an AWS VM and tried: sudo yum update Result: Error: Protected multilib versions: sendmail-8.14.4-8.12.amzn1.x86_64 != sendmail-8.14.4-7.9.amzn1.i386 You could try using ...
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1answer
167 views

How to check if a process is non-blocking in linux without using a stack tracer?

A multi-cpu server is running several processes. One process has a thread that should always be in a spinning state, using 100% of the CPU it's been assigned. My current method (besides asking the ...
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0answers
67 views

TCP packet being retransmitted 7 times when sysctl tcp_retries1 is set to 3 - why?

Ubuntu 12.04 I am trying to better understand how many times TCP will attempt to retransmit a packet when it does not receive confirmation the destination received it. After reading the tcp man page ...
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14 views

Not enough host controller resources for new device state [migrated]

I have a debian mint based system where I plug in 16 usb devices. The Kernal is: 3.11.0-12-generic After about 10 or so devices I start to experience problems with connecting new ones. There error ...
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15 views

Process identifier mask in z/OS

I've noticed a curious pattern to process identifier numbers on the z/OS system I'm working on (uname reports it as OS/390), they're either 1-4 digits long or 8 digits long but never in between. The ...
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0answers
40 views

Server crash : “unable to handle kernel paging request”

My fresh new Ubuntu webserver randomly crashes with the following error in the syslog. It doesn't respond anymore and I have to do a hard reboot. It happens almost one time a day. Server kernel is : ...
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1answer
49 views

backup files to a remote server with multiple versions using rsync hardlink option

To use rsync hard link option to backup files remotely so that remote backup server could keep multiple versions of the backups, both the link-dest directory and the target directory have to be on the ...
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1answer
36 views

Ubuntu 13.10 server has no kernels

Something has gone wrong and now we no longer have a Linux kernel (not even recovery mode) installed. GRUB is still there, but it runs the memory test. How can I fix this? Everything I've looked at ...
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1answer
22 views

In sysctl.conf settings, what is the difference between 'all' & 'default'?

In context of sysctl.conf settings, what is the difference between (all vs. default) like net.ipv4.conf.all.accept_source_route & net.ipv4.conf.default.accept_source_route in sysctl settings ? ...
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1answer
34 views

Modifications to sysctl.conf in openVZ container, do they even take effect?

I'm following a security guide(http://www.thefanclub.co.za/how-to/how-secure-ubuntu-1204-lts-server-part-1-basics) to strengthen my OpenVZ based VPS webserver running Ubuntu 12.04 , a part of that ...
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16 views

demonstrate Automatic Hardware Clock Synchronization By the Kernel (11 minute mode) without ntpd

From the man page of hwclock: This mode (we'll call it "11 minute mode") is off until something turns it on. The ntp daemon xntpd is one thing that turns it on. You can Ok, I have a ...
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1answer
20 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 ...
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1answer
54 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 ...
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1answer
1k 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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20 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 ...
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2answers
51 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
36 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 ...
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1answer
78 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
53 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 ...
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2answers
97 views

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

I'm receiving on "Linux Debian-70-wheezy-64-minimal 3.2.0-4-amd64 #1 SMP Debian 3.2.46-1+deb7u1 x86_64" this error: Message from syslogd@hostname at Feb 14 02:54:51 ... kernel:[81927.464687] Uhhuh. ...
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3answers
56 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 ...
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0answers
12 views

NFS: failed to create MNT RPC client status = -101

I am trying for network file system (nfs) booting between two systems. I am using dhcp server to assign ip-address for client. And my kernel and root file system are present in server. My client is ...
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0answers
29 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 ...
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1answer
172 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 ...
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1answer
39 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 ...
3
votes
1answer
73 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 ...
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2answers
164 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 ...
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1answer
130 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 ...
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1answer
119 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 ...
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2answers
248 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 ...
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2answers
78 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, ...
3
votes
1answer
282 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 ...
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0answers
38 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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1answer
73 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 ...
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0answers
121 views

Error: NETDEV WATCHDOG: eth0 (igb): transmit queue 2 timed out

Today, suddenly one of the network interface went down with kernel log saying: [5859423.746817] NETDEV WATCHDOG: eth0 (igb): [5859423.746818] Modules linked in: ipmi_si [5859423.746842] Pid: 0, comm: ...
0
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0answers
31 views

Process created by proc_open() is being signaled 9

Not sure if this question is appropriate for this forum but my problem is that I'm trying to run Julia interpreter using PHP proc_open() function. I'm trying to access this interpreter online using ...
2
votes
1answer
160 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
261 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 ...
3
votes
1answer
51 views

Avoid recompiling kernel modules when updating a kernel package

I currently maintain a bunch of kernel modules on my CentOS-6-like system. Suppose I want to recompile the same kernel version (Currently 3.4.56-1) to enable CONFIG_VM_EVENT_COUNTERS (or another ...
5
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1answer
128 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 ...
5
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1answer
361 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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1answer
46 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
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1answer
406 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 ...