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

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Unable to install new kernel in ubuntu server. “gzip: stdout: No space left on device” error even though abundant disk space

I am trying to install a new kernel on Ubuntu Server and I am unable to complete it due to a "gzip: stdout: no space left on device" error. The full error was produced after running sudo make ...
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1answer
24 views

Is it possible to delay booting the system after the user has pressed the power button? [on hold]

I want to delay the time after the user has pressed the power button by 10 seconds. Reasons for this is a specific machine we have built which requires other components to start sending data to the ...
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2answers
21 views

Uboot pass arguments to kernel!

How uboot can pass command line argument to kernel? I did some googling and got to know that it uses bootargs environment variable.There it was mentioned that setenv bootargs key=value.Since I am ...
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1answer
24 views

Recompile kernel without modules that are not currently in use

Is there a neat way of stripping the Linux kernel to only support the devices that are currently in use. After NVIDIA complaining about GCC version mismatch, I decided to recompile the kernel with the ...
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What is the Linux scsi mid-layer

In the Linux storage stack there are 3 levels: upper, mid and lower. Therefore, I know what it is in that sense. What I'm hoping someone will know is, what files in the Linux source tree actually ...
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23 views

Kernel address space layout

Userland address space is well documented, which includes segments like heap, stack, .text, .bss, etc. But there is not enough documentation on kernel address space. Since certain virtual address is ...
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How to send signal from kernel to user space [migrated]

My kernel module code needs to send signal [def.] to a user land program, to transfer its execution to registered signal handler. I know how to send signal between two user land processes, but I can ...
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21 views

Kernel config diffs - better way to maintain

I maintain one Linux distro (LEAF) with multiple kernel targets, so it needs to have multiple kernel configs (one reference config + usual patch files for other targets). But this adds headache on ...
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what's difference between src version 3.* and 3.*-generic

In my local Linux/Ubuntu, I have two directories for Linux src /usr/src/linux-3.16.0 /usr/src/linux-3.16.0-generic I found the code in 3.16.0 is much more than that in 3.16.0-generic. I am ...
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2answers
35 views

Wrong eUID in `/proc/PID/status` when SETUID is used

While doing a wargame challenge, I ran into an issue with permissions. The info given by /proc/PID/status is not in adequation with the permissions that should be given to the processus. I am user ...
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17 views

CPU Handling with Delayed Work [migrated]

Hey so I'm looking at this function in the kernel source code. I'm trying to figure out how Linux handles the situation where a task cannot be scheduled on the local CPU. /** * queue_delayed_work - ...
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Debian instance has two Kernels after installing Intel PCIe SSD drivers - one with Black screen

I am using Debian 8 and after installing Intel PCIe ssd drivers I noticed that the are two kernels. The kernel which has the Intel drivers installed does not display the desktop, only a black screen. ...
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76 views

RAM Disk related questions [duplicate]

there is a developed kernel subsystem that needs a chunk of memory allocated to itself that only it could manipulate this chunk. this memory should be physically contiguous and also it need the access ...
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164 views

/dev/mmcblk0 partitions limit

I've just mounted a microSD card which has 17 partitions in my laptop and I'm getting the following error in the YaST partitioner: Your disk /dev/mmcblk0 contains 17 partitions. The maximum number of ...
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1answer
25 views

Linux kernel build : shouldn't make <manufacturername>defconfig yield the same .config file?

I'm building a cross compiled 3.2.15 kernel for a Marvell Armada 370 system. The vendor's default config file for this is armada_370_v7up_defconfig. So when I perform a make ...
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How Linux kernel gets build [closed]

I am new to Linux and I would like to know how the Linux kernel gets built ? Who builds this ? I have heard that Linux gets build by programmers sitting all over the world. But it gets only released ...
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29 views

NMI received for unknown reason 20 — Do you have a strange power saving mode enabled?

I am using Debian GNU/Linux 7.8 (wheezy). While running my MATLAB program today, I got this message in terminal. Message from syslogd@sas21 at Jul 18 16:40:49 ... kernel:[1747708.091929] Uhhuh. NMI ...
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Is a disabled kernel option equivalent to not loading the corresponding module?

Suppose I set a tristate kernel configuration option to be built as a module, but I don't load the corresponding kernel module at runtime (and it doesn't get loaded automatically). Is the ...
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How to troubleshoot Fedora kernel bug

Bug 1236215, reported to the Redhat bugtracker has not gotten any attention in over 3 weeks. I'm trying to track down the cause myself, but I'm not sure how to proceed. The problem was introduced in ...
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Why does Linux scheduler have locks for run queues?

Why does Linux Kernel Scheduler code have locks for run queues? Does the scheduler spawn kernel threads, and locks are to prevent two of such threads to avoid modifying run queues at the same time?
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25 views

edit module requirements when compiling kernel

I would like to compile the realtime kernel for raspberry pi (https://github.com/emlid/linux-rt-rpi) and want to use the pi with a soundcard - the tascam us122l. The problem that I have is the ...
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5 views

Opening/Writing to a file from a KProbe handler [migrated]

I am writing a Linux kernel module using Kprobes to trace specific system calls, and I need to write to a file from within a KProbe handler (specifically, a Kretprobe). I know this is generally not ...
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26 views

Why am I able to compile kernel modules without “#include”ing the relevant header files?

Based on the common practices shouldn't I have to include <linux/stat.h> and <linux/module_param.h> in the following program? #include<linux/module.h> char str[7] = "hello"; int ...
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Giving S_IWUGO permission to module parameter results in compilation error (while S_IRUGO or S_IXUGO doesn't) - why? [migrated]

I wrote a simple kernel module to learn module_param feature of the kernel module. However, if I give the S_IWUGO, S_IRWXUGO or S_IALLUGO permissions for the perm field, I get the follwing ...
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Difference between Current and RC Kernels?

What's the difference between wget http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.2-rc1-unstable/linux-headers-4.2.0-040200rc1_4.2.0-040200rc1.201507051635_all.deb and wget ...
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38 views

Modify the graphical parts of the Android OS [closed]

I’m going through the Android kernel and Google Glass kernel, and I’m trying to find the graphical parts of the operating system. I want to modify things like the splash screen displayed while the OS ...
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1answer
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Why can the waitpid system call only be used with child processes?

The man page wait(2) states that the waitpid system call returns the ECHILD error if the specified process is not a child of the calling process. Why is this? Would waiting on a non-child process ...
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Which module utilities are the conf files in /etc/modprobe.d consulted for?

Are the conf files in /etc/modprobe.d consulted only for modprobe command or are they consulted for other module utility commands such as insmdod, rmmod, depmod etc as well? I found it mentioned in a ...
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1answer
28 views

How to confirm CONFIG setting made with make menuconfig?

I poke around make menuconfig select this, deselect that. Rebuild a linux kernel and boot up with it. How can I confirm the selection(s) I made via menuconfig exist after booting? lsmod?
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Advice on printing in kernel [closed]

What is general advice on printing in kernel level? Lately, I need to print out some internal variables in various places. However, I use a naive way using printfk to dump the stuffs I need in log ...
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Where is the RHEL7 kernel source code installed?

I install the Linux kernel source code RPM: [root@localhost ~]# rpm -ivh kernel-3.10.0-229.el7.src.rpm warning: kernel-3.10.0-229.el7.src.rpm: Header V3 RSA/SHA256 Signature, key ID f4a80eb5: NOKEY ...
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What is difference between different cpu.cfs_period_us values?

I'm reading kernel[1] docs and confused about the cpu.cfs_period_us in this part: 3. Limit a group to 20% of 1 CPU. With 50ms period, 10ms quota will be equivalent to 20% of 1 CPU. # echo ...
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Where in the kernel /dev/kmsg gets initialized?

I'm trying to figure out at which point in the boot up process /dev/kmsg gets initialized and can thus be written. On my system the first line that occurs in dmesg is printk(KERN_INFO "Initializing ...
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36 views

ACPI – how to select correct LED and LCD module

I'm facing a strange issue. I have ASUS x551ma notebook; As I can get it, after a while (20-30 min) watching LCD, I suffer eye strain. The graphics (video card) seems fine but the LED is micro-shaking ...
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How to add version number to custom kernel and rootfs?

I have a small embedded project where I had to make some minor tweaks to a linux kernel to support different hardware and minor tweaks to a debian-based operating system (my rootfs). uname -a no ...
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37 views

Custom driver for keyboard GNU/Linux 4.1.0-rc8 (Fedora)

I am writing a driver for a Logitech G110 USB keyboard for Kernel 4.1.0-rc8. My driver is perfectly loadable with insmod (Debugging message prints to dmesg that it get's initialized through ...
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1answer
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Kernel panic? After ram increase

We asked our server provider to increase ram (from 4gb to 6gb) on our server. After they increased and restarted server, it started giving these messages: Message from syslogd@www at Jul 1 14:39:04 ...
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62 views

Why does my process take too long to die?

Basically I'm using Linux 2.6.34 on PowerPC (Freescale e500mc). I have a process (a kind of Virtual Machine that was developed in-house) that uses about 2.25 G of mlocked VM. When I kill it, I notice ...
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28 views

How does rootfs.ext3 image file work?

I have a FriendlyARM mini6410 device and I have just hardly make it boot from sdcard. Now my sdcard uses "u-boot for mini" (u-boot.bin), "linux2.6.38 kernel" (zImage) and "rootfs qtopia fs" ...
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How to catch my bluetooth service events

I have usb bluetooth device which is using btusb 0.6 module (driver). The thing is I am interested to know is: how is the systemctl start bluetooth.service event invoked? I was looking info about ...
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How to determine if the kernel sources are installed?

I just bought a USB 3.0 Gigabit ethernet adapter. It uses an ASIX ax88179_178a driver. I need to build the driver and the readme says: ...you need the Linux kernel sources installed on the build ...
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64 views

Can a kernel preemption happen in the process context with `TASK_INTERRUPTIBLE` state?

If a process sets itself to the sate of TASK_INTERRUPTIBLE, can it be preempted by other kernel components? If it does, I think this process maybe lost wake-up chance due to failed to check the ...
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3answers
65 views

Legal status of an embedded Linux case

I wanted to find the source code of embedded Linux that is used in Shenzhen Apexis Electronic Co.,Ltd products. For example in this page: http://apexis.com.cn/productsdetails_244.html You see they ...
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How To Induce RO To Linux FS

I've read in several places that during I/O error to system log file most linux distributions go to read only mode. Followed by how to recover from it. This is all fine, but I'm looking for a way to ...
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64 views

4G modem on an embedded 2.6.32.9 kernel on a Parrot AR Drone 2.0

I am attempting to compile support for a Huawei E3276 usb LTE modem for an embedded Linux/BusyBox installation on a Parrot AR Drone 2.0, which is based on kernel 2.6.32; however, I am running into ...
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1answer
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How to get kernel messages on serial console on a systemd system?

I'm trying to set up an A20-OLinuXino-LIME2 as a headless fileserver with a Debian 8 image from Igor Pečovnik's builds. I would like the system to output its kernel messages to the serial console ...
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1answer
45 views

Linux process - messages from kernel [closed]

I have been learning about different IPC mechanisms present in Linux, for communication between user space processes. I want to ask what are various ways in Linux for the kernel to communicate with ...
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1answer
44 views

Booting encrypted disk kernel error: Cannot initialize device-mapper

I have Ubuntu 15.04 with a default full disk encryption installed on my chromebook Pixel with linux-samus kernel patch and everything is working fine. I've just tried compiling a newer version of the ...
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APEI Generic Hardware Error : PCIe error with ATTO SAS HBA

Recently we upgraded a remote server to a new Dell PowerEdge T630 with dual CPUs (so all PCIe slots are active). It had been running for several weeks fine before we added an IBM LTO5 tape drive that ...
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SystemTap log output to file

I want to log output from my SystemTap script to a file. But when I try to use the -o option like: stap -r $PWD --remote user@hostname -o test.txt -S 1 ./test.stp I can't find the log file. If I ...