The kernel of operating systems popularly known as Linux, or sometimes GNU/Linux.

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Configuring, compiling and installing a custom Linux kernel

I'd like to try using a kernel other than the one provided by my distro -- either from somewhere else, or as customized by me. Is this difficult or dangerous? Where do I start?
320
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7answers
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How can I find the implementations of Linux kernel system calls?

I am trying to understand how a function, say mkdir, works by looking at the kernel source. This is an attempt to understand the kernel internals and navigate between various functions. I know mkdir ...
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3answers
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kernel: Namespaces support

I am wondering what exactly the “Namespaces support” feature in the Linux kernel means. I am using kernel 3.11.1 (the newest stable kernel at this time). If I decide to disable it, will I notice any ...
5
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2answers
878 views

mount options shown in /proc/mounts

IIRC then the mount options shown in /proc/mounts have changed. Some time ago acl and user_xattr were shown, now it seems that only noacl and nouser_xattr are shown if these features are turned off. ...
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7answers
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Linux Kernel: Good beginners' tutorial [closed]

I'm interested in modifying the kernel internals, applying patches, handling device drivers and modules, for my own personal fun. Is there a comprehensive resource for kernel hacking, intended for ...
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4answers
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How to tell Linux Kernel > 3.0 to completely ignore a failing disk?

I am asking this question here in the hope that some Linux-kernel guru can have an answer. This question has been asked on AskUbuntu and on SuperUser without answers: thinking better, it is really ...
14
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3answers
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Given a git patch id, how to find out which kernel release contains it?

Assume I have some issue that was fixed by a recent patch to the official Linux git repository. I have a work around, but I’d like to undo it when a release happens that contains my the fix. I know ...
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5answers
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Kernel can't find /dev/sda file during boot

I configured a gentoo kernel (kernel-2.6.36-gentoo-r5), but when I boot it can't mount /dev/sda1: ALERT! /dev/sda1 does not exist . Dropping to a shell . I use the shell to go to the /dev ...
5
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1answer
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Running bzImage in QEMU: Unable to mount root fs on unknown-block(0.0)

I compiled the kernel by doing make menuconfig and make. I was trying to run the bzImage in qemu, by doing qemu -kernel bzImage but it didn't work out with the error message: Unable to mount root fs ...
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3answers
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Linux: How to find the device driver used for a device?

If my target has one device connected and many drivers for that device loaded, how can I understand what device is using which driver?
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7answers
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Is it possible to install the linux kernel alone?

I'm just curious if it's possible to install the linux kernel alone, or if you need to use one of the flavours. If it were possible, how would you do it? I don't need a detailed tutorial. I just want ...
24
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1answer
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How to display kernel command line parameters?

In the grub.conf configuration file I can specify command line parameters that the kernel will use, i.e.: kernel /boot/kernel-3-2-1-gentoo root=/dev/sda1 vga=791 After booting a given kernel, is ...
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1answer
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Linux: What is a tainted kernel?

Under certain conditions, the Linux kernel may become tainted. For example, loading a proprietary video driver into the kernel taints the kernel. This condition may be visible in system logs, kernel ...
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2answers
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Running Linux kernel in Virtualbox

I just built a Linux kernel on Ubuntu and now I want to make it run on VirtualBox. I wanted it to be in an img format. I created a hard drive image by doing the commands: $ qemu-img create disk.img ...
39
votes
7answers
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Why does mount require root privileges?

Why does Linux require that a user be root/using sudo/specifically authorized per mount in order to mount something? It seems like the decision as to whether to allow a user to mount something should ...
14
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1answer
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How is nice working?

sched_setscheduler says : All scheduling is preemptive: if a process with a higher static priority becomes ready to run, the currently running process will be preempted and ...
6
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5answers
521 views

Which tasks to learn and which books to read to become more skilled at Unix/Linux internals? [closed]

I recently interviewed at a major company and did well on programming questions such as: "What is the time complexity of quicksort? What is the opposite in C of malloc? What is the opposite in ...
10
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1answer
5k views

Load Linux bzImage in QEMU?

I compiled a Linux by doing make menuconfig then make and now I have compiled the most recent version of Linux. How can I load the kernel into QEMU?
9
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2answers
4k views

How to set OOM killer adjustments for daemons permanently?

Running some Linux servers with single or just a few vital system service daemons, I would like to adjust the OOM killer for those daemonized processes in case something odd happens. For example, ...
6
votes
4answers
7k views

cp vs. cat to copy a file

cp a b and cat a > b, what's the difference? In x86 install script of linux kernel's source tree (arch/x86/boot/install.sh), both are used: cat $2 > $4/vmlinuz cp $3 $4/System.map Why don't ...
5
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2answers
3k views

How to build a custom kernel? [duplicate]

I want to test an (upstream) custom kernel on Fedora. The plan so far is: use a recent fedora config as starting point, e.g. /boot/config-3.6.6-1.fc17.x86_64 lookup build dependencies lookup right ...
10
votes
2answers
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Why does Linux have poor battery life by default compared to Windows?

Is there something inherent to Linux operating systems that makes them poor managers of battery power by default? I would have thought a light distro like Lubuntu would have a clear battery life ...
7
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2answers
476 views

Strange temporary network outage in Linux

I'm facing a very annoying problem that I noticed a week from now and for which I can't find an answer: my network suddenly stops responding, usually coming back exactly 25 seconds later. I was using ...
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2answers
3k views

Change kernel parameters at runtime

While trying to fix an obscure hardware bug, it was suggested that adding a couple of parameters to the kernel might resolve the issue. I can of course do that, but I was wondering whether I can make ...
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3answers
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Can anyone explain the output of mount?

I'm getting the following output when the mount command is executed. [root@]# mount /dev/sda2 on / type ext4 (rw) proc on /proc type proc (rw) sysfs on /sys type sysfs (rw) devpts on /dev/pts type ...
7
votes
1answer
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Which Debian kernel should I install?

I've started installing Debian testing on amd64 and I've come to a screen asking me to install a kernel. It gives me a choice between linux-image-3.16-2-amd64, linux-image-amd64, and none. What is ...
7
votes
2answers
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How to compile extra files into the root directory of an Android ROM

I'm building a custom Android kernel based on the Cyanogenmod ROM's kernel source code. I'd like to add folders and files into the root folder of the OS (/). For instance, after having compiled my ...
7
votes
2answers
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What does “INFO: task XXX blocked for more than 120 seconds” exactly mean on Linux?

I had this message in my kernel log : INFO: task XXX blocked for more than 120 seconds. I would like to know what it means technically: under what conditions does the kernel display this message about ...
6
votes
1answer
565 views

What are the main differences between Unix and Linux kernels today?

I know that many of the same programs run flawlessly on top of both kernels. I know that historically, the two kernels came from different origins. I know philosophically too that they stood for ...
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2answers
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Linux kernel is not finding the initrd correctly

I had compiled a linux kernel and I wanted to debug it in QEMU. I created a file to boot from by doing the commands $ qemu-img create -f raw disk.img 200M $ mkfs.ext2 -F disk.img # mkdir /mnt/rootfs ...
3
votes
1answer
221 views

Linux kernel action upon init process exiting

Say I am writing my own init program running on a Linux kernel. What happens when my init program exits with return value 0 ? Additionally is the behaviour different if the return value is non-zero? ...
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vote
1answer
523 views

system went unresponsive and had to hard reboot

without not much load on the machine, it suddenly went busy and went unresponsive. it could not respond to keyboard or mouse movement or neither would move to another other tty's. there is some log ...
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0answers
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Building Linux driver for a network card remotely, while being connected via the same card

I realize that the title alone sounds confusing, so let me provide the context. My current Linux machine configuration is Debian 7.9 (I need this specific version) with the default kernel 3.2, which ...
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3answers
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After removing linux Grub error

I have a dual boot Windows & Linux system. I removed the Linux partition, but after that I am not able to go in to Windows XP. It is not booting. It gives me a GRUB error.
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2answers
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Entry point of linux kernel [closed]

In the linux kernel is there a file that I can start to add my code, ex. load libraries? thanks
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3answers
5k views

Does the kernel have a main() function? [closed]

I am learning device drivers and Kernel programming. According to Jonathan Corbet's book, there is no main() function in device drivers. So I two questions: Why don't we need a main() function in ...
18
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6answers
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Can ps display only non kernel processes on Linux?

How can I ask ps to display only user processes and not kernel threads? See this question to see what I mean...
12
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5answers
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Enabling IOMMU in the kernel for graphics card pass-through

Short question: How can I turn on the intel_iommu setting in the Linux kernel? I run a Debian host, using the grub2 bootloader. Documentation I've seen says to edit /boot/grub/menu.lst, which seems ...
24
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1answer
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High CPU usage with CFS?

I asked a previous question to try and isolate the source of an increase in CPU usage when moving an application from RHEL 5 to RHEL 6. The analysis that I did for that seems to indicate that it is ...
17
votes
2answers
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The UEFI & SecureBoot impact, how severe?

I'm planning to buy a new laptop in the coming days, and I'm quite impressed with new, cool Ultrabooks. As a long-time GNU/Linux user, I'll of course install a distro of my choice on it. Chances are ...
15
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1answer
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Setting CPU governor to on demand or conservative

I'm struggling with cpupower on ArchLinux. I want to set governor to ondemand or even to conservative. First if I do $ sudo cpupower frequency-info --governors, I only get performance powersave. So ...
14
votes
2answers
3k views

How many actual developers work on the Linux Kernel

For a study I am doing I was asked how many actual developers commit on a typical kernel version. I know there is Linus Torvalds as the main developer, followed by many second main developers. ...
12
votes
2answers
2k views

What does a niceness value of (-) mean?

According to the man page, and wikipedia; nice ranges from -20 to 20. Yet when I run the following command, I find some processes have a non numerical value such as (-). See the sixth column from ...
11
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4answers
10k views

Are FIFO, pipe & Unix domain socket the same thing in Linux kernel?

I heard that FIFOs are named pipes. And they have exactly the same semantics. On the other hand, I think Unix domain socket is quite similar to pipe (although I've never made use of it). So I wonder ...
9
votes
2answers
3k views

How can I know if the current kernel was compiled with a certain option enabled?

Is there a way to know if the kernel was compiled with a certain option activated (i.e. CONFIG_PROC_EVENTS=y) without having to pull out the kernel sources package and looking in the config file?
7
votes
1answer
199 views

How to enable random PIDs on Linux?

I'm currently comparing random PID implementation on OpenBSD, FreeBSD and Linux from security perspective. As long as OpenBSD and FreeBSD are concerned, my work is done. However, while the answer ...
11
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3answers
4k views

How do I get a linux kernel patch set from the mailing list?

I don't subscribe to the linux-kernel mailing list, but I want to get a set of patches that were posted a few weeks ago and apply them to my kernel for testing. I'm very familiar with patching, ...
6
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1answer
280 views

show parameters of running kernel

I would like to see with what parameters the running kernel has been started. i.e., I mean those parameters that are specified with the append option, such as ipv6.disable=1 or rootfstype=ext2 Is ...
5
votes
2answers
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File handles and filenames

I read this post. Are file descriptors the same as file handle? While trying to configure the linux kernel, it asks open by fhandle syscalls (FHANDLE) [Y/n/?]. Why is this option provided? Does ...
5
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1answer
4k views

Is it possible to run any distro from RAM from within an .iso saved on an NTFS file system?

Running entirely from RAM been done on various distros such as Slax, DamnSmallLinux, and newer Ubuntu versions, and since I have 8GB it seems reasonable that I could run many distros entirely from RAM ...