Everything about UNIX kernels: development, configuration, compilation, design, etc.

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Could the Kernel stack of a process be empty, when a process is swapped out to a disk?

I am just curious to know whether the Kernel stack could be empty when a process is swapped out to a disk or not?
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6answers
3k views

Can Linux “run out of RAM”?

I saw several posts around the web of people apparently complaining about a hosted VPS unexpectedly killing processes because they used too much RAM. How is this possible? I thought all modern OS' ...
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1k views

How can I install perf 3.4.25?

By installing perf using sudo apt-get install linux-tools-common sudo apt-get install linux-tools-3.2.0.23 gave me perf version 3.2.14 How can I install perf 3.4.25? Is it related to kernel ...
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1answer
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ACPI Errors/Exeptions, why they spam, how to know and fix it?

I've been having these errors pollute my dmesg: [21720.400079] ACPI Error: [\_TZ_.THRM] Namespace lookup failure, AE_NOT_FOUND (20130328/psargs-359) [21720.400093] ACPI Error: Method parse/execution ...
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2answers
2k views

Linux Mint Debian quits on boot

I just upgraded Linux Mint Debian Edition with the up7 package. The update manager failed initially (can't remember where...) so I ran sudo apt update, sudo apt dist-upgrade, sudo apt upgrade and ...
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2answers
182 views

Linux process “scheduling”

I've seen it written many times that the Linux scheduler schedules processes. I'm teaching a course on multithreaded programming, and would like to get my terminology straight. I have one thing I ...
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1answer
399 views

TUN/TAP Will not load

I have an OpenVZ server but can't seem to get the tun/tap module to load. I ran modprode tun on the hostnode but when I go under the VM I get: Tue Sep 24 03:08:36 2013 Note: Cannot open TUN/TAP dev ...
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92 views

Confusion with Linux kernel [closed]

I am really confused with the kernel concepts. I came to know that the kernel is between application and hardware, and that the kernel takes input from the applications and it will send the ...
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2answers
3k views

What's the difference between a kernel oops and a kernel panic?

I know what a kernel panic is, but I've also seen the term "kernel oops". I'd always thought they were the same, but maybe not. So: What is a kernel oops, and how is it different from a kernel panic? ...
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1answer
2k views

How to fix unreliable Realtek Wireless card on Ubuntu 13.04

I have a Realtek RTL8188CE wireless card and it works fine when I have a strong signal, but if I get even slightly away from the wifi I lose connectivity even though there is a strong Rx signal. I ...
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1answer
248 views

What changed between kernels 3.2 and 3.9 that affect MiniDLNA?

I'm using Debian testing, and I've problems with MiniDLNA on kernel > 3.2. The DLNA client works about 30 min, after that it lost the connection with the minidlna server and can't discover the server ...
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1answer
1k views

Features that Linux kernel has and Windows does not? [closed]

What are the significant technical features the Linux kernel has that the Windows does not? Something that I might find on a kernel feature list, which is conceptually an advantage, or significantly ...
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2answers
68 views

Is there kernel patch to prevent load files into RAM for LiveCD?

Is there kernel patch to prevent load files into RAM for LiveCD? I mean, if I'm use LiveCD with "boot to Ram" option, there is no needs for kernel to load executable binaries to RAM from RAM. It ...
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2answers
531 views

Linux kernel with absolutely no virtual memory [duplicate]

I am interested in obtaining (or building myself) a version of the Linux kernel that has absolutely no virtual memory and none of its attendant overhead. No swap file, no nothing. What are my ...
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1answer
126 views

Server pinning one core

I'm working on a server using Vert.x in Java and I'm noticing some performance problems when running on a dedicated server running Ubuntu 12.04. The server picks up the incoming HTTP requests, does ...
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1answer
1k views

How can a user run a program in kernel mode?

Is it possible for a user to run their own program in kernel mode? How could a user accomplish this? What weakness in the system's protection mechanism would they have to bypass? I'm thinking that a ...
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3answers
15k views

How to disable USB autosuspend on kernel 3.7.10 or above?

I've updated my HTPC from kernel 3.7.10 to 3.10.7 and it seems CONFIG_USB_SUSPEND is now gone from the kernel options and included in PM. The main problem I'm facing is that I have an external HDD ...
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2answers
219 views

What does it mean to install a kernel?

What does it mean to install a new version of the kernel. My Linux box gave me this message when I was updating, NOTE, 3.8.13 was the last maintained maintenance release by Greg Kroah-Hartman. ...
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2answers
187 views

Why should I build a custom kernel? [closed]

Several of my coworkers have been building custom kernels for their workstations and servers. What advantages/disadvantages are there to building a custom kernel? Why should I build a custom kernel? ...
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1answer
174 views

Using qemu to boot OpenSUSE (or any other OS) with custom kernel

I want to run OpenSUSE as guest with a custom kernel image which is on my host machine. I'm trying: $ qemu-system-x86_64 -hda opensuse.img -m 512 -kernel \ ...
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2answers
4k views

How does Linux load the 'initrd' image?

I've been trying to understand the booting process, but there's just one thing that is going over my head.. As soon as the Linux kernel has been booted and the root file system (/) mounted, ...
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4answers
3k views

How to compile the C compiler from scratch, then compile Unix/Linux from scratch

Let's say I work for a large services organisation outside the US/UK. We use UNIX and Linux servers extensively. Reading through this article it mentions that it would be easy to insert a backdoor ...
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2answers
886 views

Kernel freezes on loading ramdisk. How to find out what's wrong?

I'm using an Ubuntu Server (13.04) Minimal installation (with the Xubuntu Metapackage as a desktop environment, if that matters) on x86_64 on my Samsung notebook. I'm currently forced to use the ...
107
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3answers
8k views

What does the Windows flag in the Linux logo of kernel 3.11 mean?

I've just installed kernel-3.11.0-1.fc20 for my Fedora 19 installation. During the rebooting progress, I saw the Linux logo with a Windows flag in it, what does it mean? The Fedora 19 is installed ...
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3answers
2k views

Boot my kernel in a Virtual Machine?

I'm learning now how to compile and boot linux kernels. Is there a way to boot kernels in a virtual machine, rather than messing my system? I use VMWare Workstation on Windows 8. Can I use that to ...
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1answer
436 views

Some keys keep getting randomnly ignored when typing on my laptop keyboard

Currently, I have Arch Linux 64-bit installed on the Razer Blade Pro laptop. The only problem I have is that some keystrokes get randomly ignored when typing at normal-fast speed (above 5 keys/sec ...
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2answers
2k views

/proc/sys vs /sys/modules/mod/parameter

I've been wondering for last few days how exactly does it work. We can set kernel runtimes parameters using sysctl or echo boolen 1> /proc/sys/module/exactParameter but in ...
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2answers
17k views

Why is swappiness set to 60 by default?

I just read some stuff about swappiness on Linux. I don't understand why the default is set to 60. According to me this parameter should be set to 10 in order to reduce swap. Swap is on my hard ...
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1answer
82 views

init 0 process is not starting

Yesterday I have encountered one problem, when I turn on my PC it took a long time to boot. After booting it reached to command line with <initramfs> (It is unknown to me what it is) I thought ...
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2answers
81 views

Find or create kernel configuration of kernel binary

I've downloaded a kernel binary which I am using now. In order to use the watchdog on my system I must recompile the kernel with watchdog support. Is it possible to obtain the current kernel ...
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1answer
436 views

Kernel module blacklist not working

I'm trying to figure out how to blacklist modules, and I'm trying it on the usb storage. Unfortunatelly it seems ot have no effect, and I get the module in even if it's not used (apparently). My ...
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1answer
96 views

Booting failing in different Debian and Debian derivated distros?

I've tried Ubuntu, Linux Mint and Debian, even though all have worked great for me I'm keeping with Ubuntu, I tested 12.04, 12.10 and even 13.04. The 12.04 LTS is the one I work with. There's one ...
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4answers
100k views

How do you empty the buffers and cache on a Linux system?

Prior to doing some benchmarking work how would one free up the memory (RAM) that the Linux Kernel is consuming for its buffers and cache?
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Virtual address of Global variables in Kernel code

If my understanding is not wrong, every process has a Kernel Address space associated with it (which is typically 1GB). As far as local variables are concerned, they are assigned on the kernel stack ...
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1answer
13k views

What is difference between User space and Kernel space?

Is Kernel space used when Kernel is executing on the behalf of the user program i.e. System Call? Or is it the address space for all the Kernel threads (for example scheduler)? If it is the first ...
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2answers
1k views

busybox initramfs loop mount

I'm trying to loop mount my root filesystem (a loop file) within a busybox initramfs. I try to run the command: mount /rootfs.raw /root ... which works on my Ubuntu laptop, however, I simply get ...
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1answer
641 views

Kernel Panic after Fedora 19 Update

After installing updates on Fedora 19 (kernel 10.3.7-200.fc19.x86_64) the DE freezes whenever I log in. Using the virtual consoles doesn't work. One time I even got this kernel panic: ...
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1answer
424 views

Is “zero-copy networking” implemented by default on Linux?

I saw this article: http://lwn.net/2001/0419/kernel.php3 Zero-copy networking will be in 2.4.4. This patch, by David Miller, Alexey Kuznetsov, and others, has been in development and testing ...
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2answers
302 views

How to build my own kernel ? Where should I start? [closed]

I have completed my graduation recently. And I have only basic knowledge in C. But I would like to work on the Linux Kernel, and customize it according to my needs. Not only customize I would also ...
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1answer
393 views

How to enable VESA framebuffer as default in NetBSD 6.1

When booting NetBSD, the old Tecra 720CDT that I have, works quite nicely in 1024x768x15 mode with vesa fb. I always have to activate VESA when booting the system: > vesa on > vesa 0x116 > ...
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2answers
170 views

Linux Kernel limit access to root with a button?

Is it possible to limit the access to a root account from within the kernel? I mean that if I press a button then the system detects the button being pressed and then allows access to the root ...
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1answer
104 views

Upgrade kernel for linux system without upgrading user apps/libs?

I built a custom Linux "recovery-cd" image that consists of a compressed initrd and boots via bcdedit (like Ubuntu Wubi) instead of a physical CD. It has various recovery tools for partition editing, ...
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1answer
5k views

Messages from syslogd, what do they mean and what do I do?

Recently, these messages started popping up straight into my prompt when I'm connected to the OpenSUSE system in question via PuTTY: Message from syslogd@host at Aug 5 11:04:03 ... kernel:[ ...
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3answers
683 views

Intentional kernel panic under Linux?

Is there any way to cause a kernel panic under Linux? I've heard of echo c > /proc/sysrq-trigger but it seems to just freeze, and I'm not sure it's a kernel panic. Is there any C program I can ...
0
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1answer
374 views

Linux distro with PREEMPT_RT patch

I want to know if there is any Linux distribution with PREEMPT_RT kernel patch? If not, is there any good tutorial on how to patch and compile a kernel with RT patch and how can I create kind of a ...
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0answers
198 views

Linux server crash (kernel NULL pointer dereference + soft lockup - CPU#1 stuck)

I have a Linux 3.2.0-4-amd64 #1 SMP Debian 3.2.46-1 x86_64 GNU/Linux server that keeps crashing, usually once every 24-72 hours. I'm running lighttpd, mysql, haproxy and a couple of always-running ...
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2answers
663 views

Why CONFIG_NO_HZ is not set by default

In the Linux Kernel CONFIG_NO_HZ is not set. But an initial reading suggests that setting that option would be nice from a performance point of view. But reading some posts like this made me think ...
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1answer
176 views

Efficiency of Linux Kernel [closed]

In a documentary, Linus Torvalds says that even in the future, if anyone wishes to make a new OS from the scratch, they could use the Kernel which he wrote. It was very inspiring. Is it true that ...
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1answer
2k views

Running make with vermagic kernel string with parentheses causes /bin/sh syntax error

I am on Ubuntu Server 12.04 x86_64 and I need to build Android CyanogenMod 7.2 kernel module. My phone has custom ROM and a patched kernel: adb shell cat /proc/version yields Linux version ...
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1answer
173 views

proc/sys/vm/flush_mmap_pages missing in 3.9 kernel, how to get it?

There was an option in redHat 5.2 called flush_mmap_pages, I could set this to zero and that would turn of writing dirty pages from a mapped memory file (so I can do it myself when I want to). However ...