The linux-kernel tag has no wiki summary.
225
votes
7answers
19k views
Understanding the Linux kernel source
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 ...
44
votes
4answers
2k views
Why isn't Linux embraced as the official GNU kernel?
While I knew for quite some time the existence of Hurd, and its mission as the official GNU Operating System kernel, I was wondering how come Linux is not embraced as the official GNU kernel over the ...
26
votes
7answers
1k views
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 ...
24
votes
1answer
405 views
What would be the best way to work around this glibc problem?
I administer a Gentoo Hardened box that uses file capabilities to eliminate most of the need for setuid-root binaries (e.g. /bin/ping has CAP_NET_RAW, etc).
Infact, the only binary I have left is ...
22
votes
1answer
1k views
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 ...
18
votes
7answers
9k views
Linux Kernel: Good beginners' tutorial
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 ...
18
votes
1answer
372 views
How to get started writing drivers?
I have a throw-away cheap laptop I'd like to twiddle around, a Thinkpad SL 500.
What bothers me are two leds, the one for wireless connectivity, and the one for hibernation, which don't light up at ...
13
votes
2answers
389 views
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 ...
11
votes
4answers
373 views
Linux on a 286?
I don't own a 286 nor do I intend to run Linux on one. However since the 286 has protected mode, why is it frequently stated that Linux requires a 386 CPU or higher?
From ...
9
votes
1answer
907 views
What happens in each step of the Linux kernel-building process?
I've read many tutorials about how to build custom kernels and boot Ubuntu using those kernels, and successfully followed the guides and booted custom kernels, but I have no understanding about what ...
9
votes
3answers
2k views
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?
8
votes
2answers
525 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. ...
8
votes
2answers
1k views
minimal TCP MSS in Linux
The TCP MSS in Linux must be at least 88 (include/net/tcp.h):
/* Minimal accepted MSS. It is (60+60+8) - (20+20). */
#define TCP_MIN_MSS 88U
My question is: where did they come up with ...
8
votes
1answer
2k views
Isolating cause of higher CPU usage on RHEL 6 vs RHEL 5
I'm currently looking to move our system from RHEL 5 to RHEL 6, but I've run into a snag with unexpectedly high CPU usage on the RHEL 6 machines. It appears that this may be due at least in some part ...
7
votes
3answers
359 views
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 ...
6
votes
1answer
2k views
Does Android really use the same kernel as Linux?
I read from somewhere that Android uses the Linux Kernel. Is it really true? I thought the Linux Kernel was meant for desktop operating systems.
6
votes
2answers
647 views
An oom killer thats baffling me
I am not able to understand why would kernel issue this oom killer when I see enough memory is available:
Also why are there so many kernel cache pages allocated?
I say enough memory is available ...
6
votes
4answers
611 views
Difference between bootable and non-bootable partitions
What is the difference between a bootable and non-bootable partition? I know that a user cannot boot a system from a partition marked non-bootable and can from one marked bootable.
I want to know ...
6
votes
2answers
3k views
How to boot EFI kernel using QEMU (kvm)?
Hey guys I'm trying to emulate a EFI enviroment using QEMU (kmv), virtualbox takes 15 minutes to boot in EFI mode using archboot.
Using legacy BIOS mode I can boot using this command:
...
6
votes
2answers
5k views
Where is the struct task_struct definition in the 2.6.30.5 Linux Kernel?
In the version 2.6.15 kernel, I got that I can rewrite the task_struct in the file (include/linux/sched.h)，like:
struct task_struct {
unsigned did_exec:1;
pid_t pid;
pid_t tgid;
...
6
votes
1answer
704 views
How to debug system freeze?
I'm experiencing strange bug when I close lid of my laptop - system freezes (no reaction on keys, no response form ssh) hard and displays some strange colour effects. The kernel log (after reboot) ...
6
votes
1answer
76 views
How should I solicit feedback from a tree maintainer for patches sent to the lkml?
I have submitted a patch to the linux kernel that has gotten several reviews and gone through a couple iterations on the mailing list. It has been ACKed and reviewed by two developers, but they say ...
5
votes
1answer
1k views
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 ...
5
votes
1answer
2k views
Why does Linux show both more and less memory than I physically have installed?
I know about swap - this question isn't about that. In dmesg, the Linux (x86-64) kernel tells me this about how much memory I have:
[ 0.000000] Memory: 3890880k/4915200k available (6073k kernel ...
5
votes
5answers
320 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 ...
5
votes
3answers
248 views
Disadvantages of linux kernel module?
I am trying to understand the disadvantages of using Linux kernel modules. I understand the benefits of using them: the ability to dynamically insert code into a running system without having to ...
5
votes
1answer
726 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?
5
votes
3answers
4k views
mptscsih: ioc0: task abort: SUCCESS (rv=2002) causes 30 seconds freezing
I/O to my software RAID6 often freezes for around 30 seconds after which everything is back to normal.
After the freeze is over this is put into syslog:
Mar 14 18:43:57 server kernel: [35649.816060] ...
5
votes
2answers
1k views
how is the file /proc/net/dev filled?
So, I'm writing a kernel module that needs stats about local network interfaces and I came up with the following code ... everything works fine except for the part where I try to read wireless device ...
5
votes
3answers
377 views
Why is the theoretical RAM limit for RHEL 6 128 TB and how is this determined?
I'm studying for RHCSA and am confused by a statement I came across in some training material:
There is no practical maximum RAM, as theoretically, you could run 128 TB of RAM on RHEL 6. But ...
5
votes
1answer
230 views
Does the kernel delete entries in /dev on an initramfs?
I have a fully custom, minimal, embedded Linux (vanilla, 3.3.8, i486, Vortex86dx) system that boots from an initramfs image. No standard distribution scripts are used, just a single rcS file that does ...
5
votes
2answers
884 views
What is the appropriate value of vm.swappiness when using zram?
I'm using zram on my computer as a compressed RAM-backed swap. When the system needs to swap something out, swapping it to a zram-backed swap file is more or less equivalent to compressing that data ...
5
votes
1answer
165 views
Linux /proc/sys/kernel: where are the files sysrq-sticky, sysrq-key, and sysrq-timer?
Documentation for Red Hat Enterprise Linux 3 (section 5.3.9.3) mentions these files in /proc/sys/kernel/:
sysrq
sysrq-key
sysrq-sticky
sysrq-timer
The documentation for RHEL 5 also mentions them.
...
5
votes
1answer
246 views
Loading speedstep_centrino kernel module
Because of a noisy fan in my laptop, I need to change CPU frequency and for this task I need to load the appropriate kernel module.
The CPU in my laptop Acer TravelMate 4002WLMi is:
$ cat ...
4
votes
4answers
1k 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 ...
4
votes
3answers
332 views
Does the linux kernel (specifically 2.6 onwards) have any recursive function?
Given the limited fixed size of kernel stack, my guess is that although theoretically we might have a recursive function if its recursion doesn't go too deep, pragmatism would suggest to do away with ...
4
votes
1answer
285 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 ...
4
votes
2answers
270 views
How is a Linux kernel capable of accessing its assigned initramfs/initrd?
I'm trying to understand the boot process of a machine as a whole from the time you hit the power button. There's this one piece from bootloader to initramfs stage I don't quite understand among some ...
4
votes
3answers
383 views
How to compile my own linux kernel?
I want to learn about compiling a kernel from scratch. How can I download the latest stable Linux kernel from http://kernel.org/, compile it, and install it in a VMware virtual machine? This is just ...
4
votes
2answers
220 views
c++ programming on a Real-time linux OS
Is there any gotcha's programming RealTime C++ applications (user space and linux drivers) on RT linux kernel compare to a std linux kernel?
The Linux RT patch applies changes to kernel scheduler, ...
4
votes
3answers
661 views
How to tell of whether the kernel parameter [passed at command line] is a valid kernel parameter?
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 plasticDuck
After booting up a ...
4
votes
2answers
199 views
Why won't my Linux install boot?
It's my first time compiling a Linux kernel. Everything went well until I hit this problem. After I edit my /etc/fstab:
and edit etc/lilo.conf:
I want to set the info about crux in lilo, so I ...
4
votes
1answer
1k views
How do I convert a kernel .config file from 32-bit to 64-bit?
At this page you can download a configuration file that lets you target a particular notebook architecture during the compilation of a new 32-bit Linux kernel.
I need a 64 bit version.
What do I ...
4
votes
1answer
699 views
What is the difference between /proc/self/stack and output from pstack?
I have been looking through the documentation for /proc and the "stack" object being a new'ish object in proc, I have also looked through the kernel commit to create it -- however the documentation ...
4
votes
2answers
488 views
can't initialise/detect 16550A UART at unusual io port address
I've got a board based on the Vortex86DX CPU which is an x86 based microcontroller. It has five 16550A UARTS, four (COM1-COM4) of which are at the usual io port addresses (0x3f8, 0x2f8, 0x3e8, 0x2e8) ...
4
votes
1answer
59 views
User Mode Linux compile fails
I am trying to compile User Mode Linux on a 64 bit machine with defconfig and getting the following error.
arch/x86/um/user-offsets.c:1: sorry, unimplemented: code model "large" not supported yet
...
4
votes
1answer
120 views
How/why can Firefox packages work on all Linuxes?
How/why can a Firefox 64bit (or 32bit) package work on different Linux distributions since each Linux distribution has a different version for gcc, glibc, linux kernel, etc. ?
4
votes
1answer
183 views
After re-compiling the kernel, my grub stop after the bios
After recompiling my kernel, I copied the corresponding files to /boot, and my /boot directory looks like:
Then, I inserted a new item in grub, and /boot/grub/menu.lst now looks like:
After ...
3
votes
1answer
367 views
What does this Linux kernel trace mean?
I’m running a linux server at home which is mostly a file and e-mail server and a digital video recorder.
All the data goes on an ext4 partition on a software raid-6.
Every now and then (sometimes ...
3
votes
2answers
989 views
Adding a new System call to Linux 3.2.x with a loadable kernel module [closed]
I want to add a particular new system call in the linux kernel 3.2.x but as a loadable kernel module (as I don't want to recompile the kernel again and again)
I read through many posts on internet ...
