Questions tagged [kernel]

Linux is the name of the kernel used in Ubuntu as well as other GNU/Linux operating systems. Use this tag for questions related to upgrading and installing kernels, compiling, patches, and kernel modules.

An operating system kernel is the central part of the operating system, handling all main tasks. It is loaded into a protected area of memory at boot time. Kernel space, where the kernel carries out its tasks, and user space, where everything else happens, are kept separate. The /sys directory contains a virtual filesystem that provides a view of kernel data structures and objects from user space.

The Linux kernel is a monolithic kernel originally developed by Linus Torvalds, who still directs its development. The latest vanilla kernel can be downloaded from kernel.org, and Ubuntu kernels (patched by Ubuntu kernel team) are available from the Ubuntu mainline kernel ppa

The kernel is found in the /boot directory. When a new kernel is installed (for example, as part of a routine update and upgrade procedure) old kernels are not automatically removed, and over time the /boot directory becomes full, and this can cause serious problems if /boot is on a small separate partition. To prevent this, users should periodically run sudo apt autoremove to clean up (actually the initrd.img file for each kernel is larger than the kernel itself, but that is removed along with the kernel by autoremove). It is advisable to keep at least one "spare" older kernel. The user can select which kernel to boot from the GRUB menu. The newest kernel (with the highest release number) is booted by default.

The release number of the running kernel may by checked with the command uname -r

For more details, see the documentation maintained by the Ubuntu Kernel Team.

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Why choose a low latency kernel over a generic or real-time kernel?

After installing Ubuntu Studio 12.04, I have found that it uses a low latency kernel. I searched for an explanation and how to change back it to a real-time or generic one. However, it looks like this part of Linux hasn't been covered to explain…
Starx
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Why doesn't Ubuntu remove old kernels automatically?

I wonder why Ubuntu won't remove the old kernels automatically. Surely nothing is perfect and things can go wrong, so in case a update doesn't work, having a backup kernel maybe great. But it would also suffice to just keep the latest kernel and…
Registered User
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How can I temporarily disable ASLR (Address space layout randomization)?

I am using Ubuntu 12.04 32-bits, for some experiment I need to disable ASLR; how do I accomplish that? What should I do after that to enable ASLR again?
Am1rr3zA
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How can I determine the version of the running kernel?

How can I determine the version of the running kernel?
Brad Figg
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How to restore a system after accidentally removing all kernels?

I was trying to delete old kernels, but I must have deleted all of the kernels on my Ubuntu 11.04 laptop. Is there any way to fix this via USB boot or mounting hard drive on another system?
Eric Truett
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What is the meaning of 'i686' in Ubuntu?

To check whether I am using 32bit or 64bit Ubuntu. I looked in How do I check if I have a 32-bit or a 64-bit OS? and found this answer uname -a. If it is shown as i386, it will be 32bit and amd64, it will be 64 bit, but I got this result: Linux…
Mukund
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What is the linux-image-extra package for and do I need it?

I occasionally update my kernel from this web site http://kernel.ubuntu.com/~kernel-ppa/mainline/ I have been always downloading 3 deb files for installing linux header all, linux image and linux headers. I noticed one more deb file recently for…
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How to blacklist kernel modules?

How do I disable loading of unnecessary kernel modules. Kernel 3.2.4
Ringtail
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OOM killer not working?

For what I understand, when the system is close to have no free memory, the kernel should start to kill processes to regain some memory. But in my system this does not happen at all. Suppose a simple script that just allocates much more memory than…
Salem
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What is kernel panic?

I just completed an OS course. I heard the phrase "kernel panic" a lot. Can you explain What is a kernel panic? Why does it occur? How can I find out that a kernel panic occurred? What effect does it have on the system? Does it only occur in…
user
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Can I install Linux kernel in Ubuntu appart of the default one?

Can we install the latest kernel 3.4 in Kubuntu or Ubuntu 12.04 LTS? If not then please clarify the reason.
Ravi
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Why is it unsafe to delete old kernels?

I have run out of space on my boot drive, so I decided to remove old kernels. I found this page which describes exactly what I should do: Lubuntu Documentation: Remove Old Kernels. I have deleted the oldest kernel manually and now it is okay, but I…
Sergei
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Why are there so many "linux-" kernel packages on my machine, and what do they all do?

In my usage of Ubuntu, I have noticed a baffling array of different Linux kernel packages. Some of them are listed…
fouric
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How do I get the kernel source code?

I am planning to write some device drivers and I need to get the Linux kernel source. My Linux kernel version is 3.2.0-23-generic-pae and I downloaded the image from this. In many of the articles I have read, it tells me that I need to have the…
Sab
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What is a "Asking for cache data failed" warning?

I'm installing Ubuntu server 12.04 on Dell laptop and I frequently get an message as below: 3256.362200] sd 5:0:0:0: [sdb] Asking for cache data failed [3256.362200] sd 5:0:0:0: [sdb] Assuming drive cache : write through What does this message…
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