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

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Getting correct perf version

I'm trying to run perf on my Ubuntu Precise box, which I recently upgraded to kernel 3.11.10-03111002 (manual install). The problem is that perf and kernel versions must match, and the requested ...
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140 views

Kernel 3.13 on Ubuntu ARM + Android kernel options compatibility

I've installed ubuntu 12.04 LTS with the kernel 3.13 on my ARM Samsung / Google Chromebook,using this tutorial : http://www.virtualopensystems.com/en/solutions/guides/kvm-on-chromebook/ I have to ...
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3answers
157 views

Why does boot from SD card with my custom kernel result in “VFS: Cannot open root device”?

I'm using an embedded board ARM9 SAM9G25. I want to boot from SD card. When I build a linux kernel with a built-in rootfs (initramfs) then it boots. I want to separate the kernel from rootfs and I ...
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1k views

kernel: “echo 0 > /proc/sys/kernel/hung_task_timeout_secs”

I got this errors in syslog. Any idea what does it mean? The system is running on Ubuntu 12.04, kernel: 3.8.0-35-generic #52~precise1 It looks to me like failure when trying to write to disk... ...
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90 views

Having difficulties mounting a rootfs for an embedded Linux

I want my Kernel to start a squashfs rootfs for an embedded Linux. The squashfs file is on a sdcard, therefor i put these parameters on it's command line: console=ttyS0,115200 root=/dev/sdb1 rw ...
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1answer
89 views

Does using noatime on modern Linux make sense?

Starting from version 2.6.30 (which was released 5 years ago), Linux has the option relatime enabled by default. It means updates of file access time are very infrequent and prudent. But I still see ...
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2answers
128 views

What is the difference between a patch which reverts a commit and a “reversed patch”?

Before May 6th, 2013, the fs/eventpoll.c file in the Linux kernel had the following line #1605: if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS)) On May 6th, a commit changes this to ...
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1answer
61 views

What is not accessible from userspace?

I read somewhere (3.1.3) that there's a high ring (supervisor mode) and a low ring (user mode) and that some "things" can be run only from the highest ring. What do they mean by "things"? I'd guess ...
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663 views

“Memory corruption detected in low memory” kernel messages?

I have some memory corruption detected in low memory messages. I have read about it here, but I'm afraid I can't really make anything out of the discussion. It does indeed happen when I ...
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63 views

How long do dentries stay in the dcache?

On Linux, when I create a new file and open it, an entry about it is created in the dcache's hash table, right? How long does that entry stay there? Does it get removed when nothing is currently using ...
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123 views

ck patch for Linux 3.13 [closed]

Does anyone have any news about the -ck patches for Linux 3.13 kernel tree? I've checked here but there's nothing yet...
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41 views

RHEL6: Failed Dependencies when installing a package

Hi I'm getting errors when forcing to install unixODBC package on RHEL 6 here is the following error: http://flic.kr/p/jBEFvP I don't know where to get the following packages that were needed by the ...
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81 views

Issue with Hugepage reservation in linux

I have reserved hugepages for my process using below commands: #echo 64 > /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages #mkdir -p /mnt/huge && mount -t hugetlbfs nodev /mnt/huge ...
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47 views

Recommendation for kernel config UEVENT_HELPER_PATH?

I use Gentoo Linux. Historically the kernel configuration UEVENT_HELPER_PATH to hotplug, then later to udevadm. Mine has been set to /path/to/udevadm, but I've had problems in the past on Gentoo ...
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1answer
71 views

Embedded Linux: Which machine directory to pick in /arch/arm?

I am just starting out with embedded Android drivers, so any help would be great. I haven't found a lot of resources online. At the moment, I am working through a tutorial on porting a driver, and ...
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1answer
2k views

What do the kernel parameters acpi_osi=linux and acpi_backlight=vendor do?

I had troubles with the screen brightness control in my laptop and I fixed it by adding the acpi_osi=linux and acpi_backlight=vendorparameters to the filegrub.cfg. I'd like to know what these ...
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2answers
84 views

why do I need to patch linux kernel to use pandaboard's spi?

I believe this question is a bit more general but here is how it goes : I have read this article about using pandaboard's SPI, especially the part "Configuring and patching the kernel". It says that ...
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199 views

Resolving executable user stack trace addresses in ftrace

I'm trying to obtain a user stack trace in ftrace, but for some reason, only my user program cannot resolve the addresses to symbols. First, the OS I'm using is: $ uname -a Linux mypc ...
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700 views

Observing a hard-disk write in kernel space (with drivers/modules)

Apologies in advance if this post is a bit dense/messy, but I'm having a hard time formulating it better... Basically, I would like to study what happens upon a hard disk write, and I'd like to know: ...
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2answers
203 views

In a UID namespace, can I setuid to an unmapped UID?

Suppose I'm user ID 1000. I run a program inside a UID namespace, mapping UID 0 inside the namespace to UID 1000 outside the namespace. The program then attempts to change its own UID to 50, which ...
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1answer
548 views

How to fix make error “No rule to make target 'menuconfig'” when building a kernel for Beagleboard?

The aim is to build and install the USB Video Class (UVC) module, via make modules_install. I'm trying to configure the kernel via make menuconfig on Angstrom distribution, running on BeagleBoard-xM. ...
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118 views

Change the root filesystem on an embedded system

I'm using Buildroot to generate an embedded Linux with a kernel v. 2.6.39, which in the end starts busybox. Everything works fine when building with Initramfs as "rootfs". But Initramfs isn't the best ...
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1answer
94 views

Why do the data and code segments completely overlap in Linux?

Context: I'm reading "Understanding the Linux kernel, 3d ed", which uses the 2.6.11 kernel. Question: As I understand, the physical address is obtained by translating the linear address, which is ...
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339 views

Why does the Linux kernel report “out of disk space” when in reality it is out of i-nodes

A friend of mine who likes programming in the Linux environment, but doesn't know much about the administration of Linux recently ran into a problem where his OS (Ubuntu) was reporting "out of disk ...
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1answer
129 views

How to build a basic embedded linux on a Qualcomm router?

Not knowing the first thing on how to build a minimal linux system on an embedded device, I'd like to get some pointers in the right direction. Generally speaking, I'd like to know what are the ...
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1answer
193 views

moving from user mode to kernel mode

I read the following: "All processes begin execution in user mode, and they switch to kernel mode only when obtaining a service provided by the kernel." When it says "obtaining a service ...
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173 views

Compiling Linux and Creating Bootable ISO Image

I have already compiled Linux kernel 3.12.6 but did not install it into /boot as I did not want my hard disk to have another OS. I have the compiled bzImage and I don't know how to take that and ...
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1answer
44 views

Make Install Linux Kernel Location Change

I have already run make to compile the Linux Kernel 3.12.6, but when I run make install, I don't want it to install it in /boot (as I don't want another OS on the hard disk). How can I change it so it ...
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5answers
268 views

On executable files in Linux [closed]

It is said that in linux, unlike Windows, there's not a clear border between executables and other files. Well, in Windows, I write a C++ program, then it is precompiled, compiled and then linked to ...
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2answers
335 views

GRE supported in kernel but iproute2 cant create GRE tunnel

Im trying to create IP over GRE tunnel but i get No such device: ip tunnel add gre0 mode gre remote 192.168.152.22 local 192.168.152.21 ttl 255 ioctl: No such device I have compiled GRE support in ...
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83 views

LVM RAID 1 for root [closed]

I have LVM RAID 1 (not mdadm RAID 1, but exactly LVM2 RAID 1) for my root partition. I would like to make my system boot without either of the HDDs where the underlying PVs of the root LVM partition ...
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62 views

SELinux and Trusted OS - can SELinux be confined to hardware level root?

I am exploring on SE Linux and while doing so i found it as an example of Trusted OS. Is it really an example of Trusted OS stack like TrouSerS ? SELinux as per my understanding modifies the Linux ...
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1answer
154 views

No usable clock interface found

I just finished installing a paravirtualized archlinux guest on xen. I get the following error when my guest boots: [1.185226] i8042: No controller found [1.1247134] drivers/rtc/hctosys.c: ...
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1answer
153 views

Is there a command to switch to into an existing namespace?

I am using multiple UTS namespaces, each of them has some servers constantly running. I can get the namespace IDs via readlink /proc/<pid>/ns/uts, now I would like to change into a given ...
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271 views

how do I include the qcserial module in the kernel?

I need a kernel compiled, featuring the qcserial module to have support for the Huawei EM 680 model (Gobi 3000). I got kernel 3.11.6 and can find the appropriate source file in ...
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2answers
87 views

Which runlevel is best for a Linux (Debian) server (DBMS/SCM)?

I currently try to harden the system and the security of a Debian server running a database and a source code management. I just want networking and me (one user) to be able to login. Which runlevel ...
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45 views

Detach keyboard from the kernel

I am writing a remote controller app for an octocopter and want to use a keyboard as an input device for this app but I don't want it to have any effect outside this app. Somehow I would like to make ...
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2answers
127 views

Location of the kernel binary (when not in /boot)?

I failed to find the kernel binary in the standard location in /boot. I've also searched the whole file system for vmlinux or bzimage find / -iname vmlin* find / -iname bzimage However, this is an ...
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120 views

How to run just linux kernel in vmware?

I am VERY new to Linux and am wondering if you can just boot the Linux kernel by itself or does it absolutely HAVE to be apart of an operating system. My reasoning behind wanting to do this is so that ...
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189 views

Computer wont boot with any media after installing wine on Ubuntu 13.10

Yup. I can boot into anything (meaning the os part), like a cd/dvd, a live usb, or the os on the HDD. i can boot into the first screen, which i think is called the grub selection screen and whatever ...
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0answers
71 views

How can I automatically include all firmware needed by selected Linux kernel modules

I have certain modules which I need compiled into the kernel. Some of these modules require firmware, which used to be automatically included from /usr/src/linux/firmware/. However, no new firmware ...
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1answer
193 views

How can I run gdb in one machine and run kgdb kernel in another machine?

I want to run two machine: debugged machine: compiled kernel with kgdb option. debugger machine: for running gdb How can I debug machine 1 from machine 2?
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2answers
297 views

How does udev get device numbers for the devices it creates?

Spun off from a small exchange in chat. One of the primary advantages of udev is that you don't have to worry about major and minor device number exhaustion anymore. But the devices created by udev ...
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144 views

IOMMU causing freezes, disabling causes USB to not work

I'm somewhat new to linux, but I'm running a Xubuntu machine that I recently built. Since I started it up, I had noticed frequent freezes, where both the screen (if plugged in) and any SSH session ...
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302 views

Qemu: No file system could mount root (unable to mount roofs)

In Linux, I've created the root file system (rootfs) by following commands: dd if=/dev/zero of=ramdisk.img bs=1M count=4 mkfs.ext2 ramdisk.img sudo mount -o loop ramdisk.img rootfs sudo cp init ...
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Kernel IPsec SA database: FIFO instead of LIFO

When processing an IP packet, the kernel looks into the security policy (SP) database to determine whether it is to be protected with IPsec. If the identifiers of the packet (e.g. IP addresses, etc.) ...
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2answers
199 views

How do I apply parameters to specific kernels with GRUB 2?

I have several kernels in /boot. One of them, linux-cc, is for heavy computation, i.e., 100Hz, no preemption, no graphics. I've created a systemd target, named compute.target, that only brings the ...
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CentOS kernel version 2.6.32-431.el6.x86_64 bugs

As far as I updated my centos ver 6.4 to 6.5, the new kernel (2.6.32-431.el6.x86_64) disappointed me! It hangs when I want to plug my external hard to laptop or hangs when I start virtual windows 7 ...
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2answers
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Installing a cross-toolchain to build ARM binaries on Debian

I tried to install a cross toolchain so I could build Linux kernel on amd64 (Debian testing "jessie") for my ARM system. I have this entry in sources.list: deb http://www.emdebian.org/debian sid main ...
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when update kernels do they close bugs?

I'm not an expert in linux but when I upgrade my kernel to latest stable one which is 3.12.2, does it close all security bugs? How linux security bugs be closed? by installing newer kernel or how ...