for questions concerning Ubuntu's kernel, including compiling and questions relating to modules

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364
votes
34answers
412k views

How do I remove old kernel versions to clean up the boot menu?

Every time I install a new Linux kernel, it gets left in the grub_config, making the boot menu longer each time. I know I can manually search through the installed packages and remove them. Does ...
103
votes
5answers
74k views

Why is swap being used even though I have plenty of free RAM?

I thought the whole essence of swap was to act as a temporary storage safety net when RAM was full but my swap partition is constantly being used even though I sometimes have as much as 3GB free RAM. ...
88
votes
3answers
70k views

Can't upgrade due to low disk space on /boot

I try to do do-release-upgrade but then I get: Not enough free disk space The upgrade has aborted. The upgrade needs a total of 25.7 M free space on disk '/boot'. Please free at least an ...
76
votes
7answers
274k views

How can I install on a non-PAE CPU? (error “Kernel requires features not present on the CPU: PAE”)

After burning Ubuntu 12.04 to a CD, I tried booting and got the message: This kernel requires the following features not present on the CPU: pae Unable to boot - please use a kernel appropriate for ...
75
votes
2answers
63k views

How do I re-run boot loader?

Running sudo apt-get -f install said that The link /vmlinuz.old is a damaged link and: you may need to re-run your boot loader[grub] Here's the full output: user@chrubuntu:~$ sudo apt-get -f ...
73
votes
4answers
100k views

What is the safest way to clean up /boot partition?

I've got 200 MB assigned for the /boot partition. Everytime I try to update the kernel I get an error message that basically says the size of /boot is full. What can I do to cleanup /boot and ...
69
votes
8answers
235k views

What is the path to the kernel headers so I can install vmware?

I installed the VMware bundle on my Ubuntu 11.04 successfully but when I open it it gives me this window and I don't know the path to this C headers.
67
votes
10answers
89k views

Desktop does not show when I installed nvidia drivers!

The desktop does not show after I installed nvidia experimental drivers. I tried nvidia simple proprietary drivers, and they did not work either. Here is how it looks. This is not cropped or any ...
65
votes
6answers
10k views

How do we get this magic performance-boosting 200 line patch?

I read today on Phoronix that there is a 200 line patch to the Linux Kernel which dramatically improves desktop responsiveness. How can Ubuntu users get this in a way that's supported?
64
votes
6answers
14k views

How is 'rm -rf /' able to delete all files in the system?

I haven't tried this command on Ubuntu (for obvious reasons) so I am not sure if Ubuntu will allow its execution. But it's famous for deleting everything. Just out of curiosity, what happens when the ...
61
votes
8answers
22k views

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 ...
59
votes
8answers
205k views

How to update kernel to the latest mainline version without any Distro-upgrade?

Currently I'm running Linux-3.0 and I want to update it to Linux-3.3.1 the latest stable kernel release as mentioned at http://www.kernel.org. Can I update to 3.3.1 in Ubuntu without any risk of ...
58
votes
12answers
105k views

Error: kernel headers not found. (But they are in place)

I'm trying to install the Guest Additions in VirtualBox 4.04. Host OS is Ubuntu desktop 11.04 64bit, guest OS is Ubuntu server 11.10 64bit. $ sudo ./VBoxLinuxAdditions.run After some output this ...
56
votes
9answers
65k views

Does Ubuntu support USB 3.0?

I have a Western Digital My Book 3.0 - 1 TB USB 3.0 Desktop External Hard Drive, and I wanted to know if it would work on Ubuntu 10.10 Maverick Meerkat.
53
votes
4answers
76k views

Why to choose low latency kernel over generic or realtime ones?

After installing Ubuntu Studio 12.04, I found that it uses a low latency kernel. I searched why and how to change back to realtime or generic ones. But, looks like this part of Linux hasn't been ...
52
votes
3answers
86k views

How do I add a kernel boot parameter?

I need to add the boot parameter foo=bar to my kernel. How can I do this once for testing, and permanently if testing was a success?
48
votes
4answers
190k views

How do I install kernel header files?

i want to write a device driver but not able to find the header file can someone please help me find them?Also if someone can point out some important site links that would be really appreciated
48
votes
4answers
161k views

Boot Error - ACPI PCC Probe Failed

ACPI PCC Probe Failed is the error that pops up instead of the default GRUB loader after I updated my kernel to 3.19. I searched around and couldn't find much information except that it is a known ...
48
votes
4answers
28k views

How do I install and use flashcache/bcache to cache HDD to SSD?

I want to know if there is anyone who has tried installing and running their kernel built with flashcache or bcache for SSD caching? How did you manage to do it?
45
votes
3answers
112k views

How do I find out the kernel version I am running?

"The path to previous driver is usually /lib/modules//kernel/net/wireless" I need this info so I can finish updating my STA broadcom wireless. However, I'm a noob at Ubuntu and I'm not sure how to ...
45
votes
1answer
2k views

What is Ubuntu's policy on keeping old kernels

I've just run out of disk space on /. Looking into the situation I realised that since first installing 12.04, Ubuntu has upgraded the kernel ~23 times and has kept every old kernel, binaries and ...
43
votes
4answers
40k views

How can I determine the version of the running kernel?

How can I determine the version of the running kernel?
41
votes
4answers
65k views

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?
40
votes
2answers
22k views

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 ...
39
votes
2answers
3k views

Does the removal of i386 from the kernel mean Ubuntu is dropping 32 bit support?

I saw recently that the i386 CPU is not going to be supported in the Linux Kernel 3.8 so does that mean that Ubuntu will only be available in the coming years in 64-bit?
39
votes
1answer
29k views

Is “laptop-mode-tools” still relevant for 12.04 and the 3.x kernels?

I'm using Ubuntu 12.04 x64 and trying to choose power management software. Laptop-mode-tools have a lot of features, but the only reason why I'm worry about is that it's manual and config files are ...
38
votes
3answers
20k views

Should I upgrade to the “mainline” kernels?

Newer "mainline" versions of the kernel are available from the Ubuntu kernel team, e.g. 3.4 and 3.5, while Ubuntu 12.04 is on 3.2. What are the mainline kernels? Are they better than my existing ...
37
votes
3answers
42k views

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.
35
votes
4answers
3k views

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 ...
35
votes
5answers
68k views

How can I upgrade the Ubuntu LTS kernel to newer?

I just installed Ubuntu 12.04.2 64-bit on my desktop PC and I see the kernel in System Monitor is 3.5.0-23 but in Ubuntu 12.04.2 in my laptop the kernel is 3.2.0-38. I have already tried to run the ...
34
votes
3answers
60k views

What does the kernel boot parameter “set acpi_osi=Linux” do?

I am facing an issue with brightness control in my laptop which has Intel HD graphics and Ubuntu 10.10 64-bit. So when I searched for a fix I found that a common suggestion is to edit the GRUB file ...
33
votes
5answers
22k views

Does Ubuntu have support for the TRIM command for use with SSD?

SSD drives need to be "cleared/reset" after the drive fills up to maintain performance. This is done through the TRIM command for new SSD drives. Does Ubuntu support the TRIM command (through hdparm ...
33
votes
2answers
30k views

How do I disable the blank console “screensaver” on Ubuntu Server?

How to disable blank screensaver on Ubuntu Server? There's no desktop or X, only console (command-line interface).
31
votes
6answers
58k views

VirtualBox doesn't load after 12.04 upgrade

After upgrading from 11.10 to 12.04, virtual box stopped working. I've run the following to try to fix it: sudo aptitude update sudo aptitude install dkms sudo /etc/init.d/vboxdrv setup but when ...
31
votes
1answer
12k views

What is hardware enablement (HWE)?

I see the linux-hwe-generic package as part of the kernels you can install in Ubuntu 12.04. What is hardware enablement (HWE)?
31
votes
2answers
24k views

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 ...
31
votes
5answers
11k views

Why doesn't apt-get autoremove remove my old kernels?

My boot partition is on a SSD, so it doesn't have room for more than about 8 installed kernel versions, and eventually some kernel update will fail to install because my boot partition is full of old ...
31
votes
5answers
6k views

Why does Ubuntu need to update its kernel so often?

What are the advantages for updating so often?
29
votes
4answers
61k views

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 ...
29
votes
1answer
11k views

What are the differences between linux-generic, linux-server and linux-virtual kernel packages?

I'm getting new VMs built for development and staging environments, and was wondering whether there are compelling reasons for or against using the linux-virtual package on all of these images. Do ...
29
votes
2answers
37k views

How to force installation of kernel updates when using apt-get upgrade?

To update my server I use apt-get upgrade. But when there are kernel updates I always need to do apt-get install linux-.... because apt-get update does not install them. Is there a way I can tell it ...
28
votes
5answers
21k views

Will Linux Kernel 3.5 be coming to 12.04?

I'm wondering if Kernel 3.5 or 3.6 will be available for Ubuntu 12.04 when the Kernel is officially released?
28
votes
6answers
19k views

High temperature in a AMD Radeon HD4000/3000 series after upgrade

I was running 12.04 with Unity 3D for 6 months; my laptop ran almost silently and cool enough to hold on my lap with ~4 hours of battery life. I updated to 12.10 and switched to the Gnome 3 Shell. Now ...
27
votes
3answers
3k views

What are the differences between the Ubuntu shipped kernel and the upstream kernel?

What are the differences in feature set between the main Linux kernel and the kernel being used by Ubuntu? Why is Ubuntu branched off of the main kernel instead of using the main kernel directly?
25
votes
2answers
27k views

What's a simple way to recompile the kernel?

I'm interested in compiling a new kernel under Ubuntu 12.04 x86 64 bit. I found this wiki page which is basically a mirror for this blog and there are a lot of steps (git, etc.) that appear useless ...
24
votes
9answers
49k views

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 ...
24
votes
3answers
22k views

What's the meaning of “-pae” at the end of kernel version?

Last time I installed Ubuntu there was a "-pae" at the end of the kernel version in the boot screen. Now that I've reinstalled Ubuntu from the same disk instead of "-pae" there is a "-generic" at the ...
24
votes
5answers
185k views

Kernel requires an x86-64 CPU, but only detected an i686 CPU. How can I install Lubuntu/Ubuntu?

I'm trying to install Lubuntu on my laptop (sorta old 2005). [Laptop stats: Intel® Celeron® CPU 410 @ 1.46 GHz 1.47GHz, 448 MB of RAM] I press Install and this message appears: This kernel requires ...
23
votes
4answers
58k views

How do I clean or disable the memory cache?

After the system starts, in a few minutes my memory cache fills up and it starts using the swap. Here's a screenshot of /proc/meminfo. However, if I can disable this process / clean the cache once ...
23
votes
6answers
66k views

Kernel Panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)

Upon trying to upgrade from 10.10 to 11.04 all seemed to go well until the restart. This error message is what comes up: Kernel Panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0) ...