Remove Old Kernels In Ubuntu With One Command

October 2, 2010 by
Filed under: command line, HowTo, linux, Ubuntu 

A while back I wrote a post on how to remove old kernels from your Ubuntu system. While that process works just fine, it is a four step process. One person who read that post left a comment with a nice command line one-liner that removes all but the currently running kernel. And while that one-liner works quite well, I must admit that I don't understand all the regular expressions used in it, so I decided to try and come up with my own one-liner to remove the old kernels from my system.

I'm going to take you through this step by step so you can see how the individual commands in this one-liner tie together. If you're impatient, you can skip to the end to see the final command.

Step 1) List all packages that start with "linux-"

We'll use the dpkg command with the -l switch to list the packages, whether installed or not, that start with the string linux-.

dpkg -l linux-*

Step 2) Filter that list to show only installed packages

To filter the list, I'm going to pipeline the output of the first command into the awk command. I'm also going to use awk to filter out everything but the package names.

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dpkg -l linux-* | awk '/^ii/{ print $2 }'

Step 3) Filter out packages for the currently running kernel

OK, so now I'm down to a pretty limited number of packages, but I don't want to remove the packages for my currently running kernel. I'm going to use a few commands to do that. First off, I can determine my currently running kernel with the uname -r command. Currently on my system that command outputs: 2.6.32-25-generic.

To do my package filtering, I only want the numeric portion of that output. I'll pipeline the output of uname -r and use the cut command with a hyphen as the field delimiter. I'll cut fields 1 & 2.

uname -r | cut -f1,2 -d"-"

Now I'm going to use this result as the filter for a grep command. In Linux, to use the result of one command as an argument in another command, you enclose the command in single back-quotes ( ` that's the key to the left of the 1 on a standard US keyboard). So here's my one-liner so far.

dpkg -l linux-* | awk '/^ii/{ print $2}' | grep -v -e `uname -r | cut -f1,2 -d"-"`

This is the output so far on my system:

linux-firmware
linux-generic
linux-headers-2.6.32-24
linux-headers-2.6.32-24-generic
linux-headers-generic
linux-image-2.6.32-24-generic
linux-image-generic
linux-libc-dev
linux-sound-base

Step 4) Filter the list for only the kernel packages

So now I have a package list that excludes the packages for my current kernel. The only packages from the list above that I want to remove are: linux-headers-2.6.32-24, linux-headers-2.6.32-24-generic, linux-image-2.6.32-24-generic.

What makes these packages unique from the others in the list is that they all contain numbers. So I can use grep again to filter the list down to only packages with numbers in their names. I'll pipeline the output of the previous command into grep -e [0-9].

dpkg -l linux-* | awk '/^ii/{ print $2}' | grep -v -e `uname -r | cut -f1,2 -d"-"` | grep -e [0-9]

So now the output on my system is only the following:

linux-headers-2.6.32-24
linux-headers-2.6.32-24-generic
linux-image-2.6.32-24-generic

Step 5) Make sure we don't catch any stray packages

Some people have had problems with this one-liner catching the linux-libc-dev:amd64 package. Adding a

grep -E "(image|headers)"

to the string fixes the problem. Now we have

dpkg -l linux-* | awk '/^ii/{ print $2}' | grep -v -e `uname -r | cut -f1,2 -d"-"` | grep -e [0-9] | grep -E "(image|headers)"

Step 6) Putting it all together: Removing the packages

So now that I have a good list of packages I can use another pipe and the xargs command to invoke apt-get to remove the packages. First I'm going to show it using the --dry-run switch with apt-get. That way you can give it a try without actually changing your system.

dpkg -l linux-* | awk '/^ii/{ print $2}' | grep -v -e `uname -r | cut -f1,2 -d"-"` | grep -e [0-9] | grep -E "(image|headers)" | xargs sudo apt-get --dry-run remove

If everything looks good after the dry run, you can go ahead and remove the old kernels with:

dpkg -l linux-* | awk '/^ii/{ print $2}' | grep -v -e `uname -r | cut -f1,2 -d"-"` | grep -e [0-9] | grep -E "(image|headers)" | xargs sudo apt-get -y purge

So there you have it. One command, albeit a long one, to remove the old kernels from your Ubuntu system. I imagine the same command should work on other Debian based systems as well, but I've only tested this on my 32 bit system. I'd be interested to know if it works just as well on a 64 bit system.

Update: It works just fine on 64 bit systems as well.

Comments

77 Responses to “Remove Old Kernels In Ubuntu With One Command”

  1. kim jong oun says:

    this worked a treat. my /boot was full and giving issues on ubuntu 12.04.04 AMD 64bit. i was crapping myself trying to fix this, but the one liner worked!

  2. john herring says:

    Thank you so much for this command. It worked perfectly! I had searched for hours to find a simple solution to the boot space problem.

  3. CJ says:

    After confirming with "--dry-run remove" that only images and headers would be removed in my 12.04 64 bit system, I pulled the trigger.
    The last line of the result is "Do you want to continue [Y/n]? Abort." and I'm returned to the prompt as if I'd aborted the command.
    Haven't got a clue what went wrong.

    This command:
    dpkg -l linux-* | awk '/^ii/{ print $2}' | grep -v -e `uname -r | cut -f1,2 -d"-"` | grep -e [0-9] | grep -E "(image|headers)" | xargs sudo apt-get remove

    • Linerd says:

      Thanks for your comment.

      So, inserting a

      grep -v libc

      will fix it in the case of libc-dev:amd64. Maybe I should make it so it only includes packages that start with "linux-image" or "linux-headers", just in case some other problem package shows up. I can do that by adding

      grep -E "(image|headers)"
      • P B says:

        Cheers for that. Maybe you could modify the date at the top of the page. It currently says October 2nd 2010 which gives a first impression that it's 3 years old. And under the Updates include this latest tweak.
        Regards

  4. P B says:

    It is only supposed to match kernel related packages but it is also finding packages like linux-libc-dev:amd64. As it begins with linux and has a number. People could get caught out with this and
    remove things they dont want removing.

  5. Augusto says:

    You are awesome
    You wrote this post three years ago and it is working
    thanks so much

  6. Van Bastos says:

    I love you man. hahaha it really worked.

    Thanks for you very long command

    "dpkg -l linux-* | awk '/^ii/{ print $2}' | grep -v -e `uname -r | cut -f1,2 -d"-"` | grep -e [0-9] | xargs sudo apt-get -y purge"

  7. Skidder says:

    Thanks for this helpful command! However, I have one remark:

    I also have linux-libc-dev:amd64 installed, which became a candidate for removal because of the last check "only keep items with numbers in them". Of course, including "grep -v libc" in the command solved this.

    • Some Dummy says:

      Or cut -f1,1 -d":". Also it may help to pray that the Linux people choose not to use numbers in any other necessary packages.

  8. Vitalie Ciubotaru says:

    a nice command line one-liner that removes all but the currently running kernel
    While this is an accurate description, it might not be what we want. Imagine the following situation:
    1. I do `sudo apt-get update` and see that a new kernel is available.
    2. I install the new kernel. I don't reboot (why would I, if everything works fine?)
    3. I realize that I have a bunch of older kernels in my system. I want to remove them.
    4. I run this one-liner. Instead of deleting everything except the newest kernel, it deletes everything except the currently running one. No gain.

    • Linerd says:

      Why do you say no gain? You still got rid of all of those old kernels, didn't you? And removing the running kernel certainly seems like a bad idea. In your scenario, the next time you install updates you should get the new kernel again. Now you only have one extra kernel rather than 5 or 10.

  9. vacri says:

    Be careful, this will hit other packages as well - on my system (ubuntu 13.04) it also grabs "linux-libc-dev:amd64".

    ... which is pretty much what Rambo just said.

  10. Rambo says:

    Hmm I think it willl work on a 64 system, im currently in the process of adjusting it a little though. The trick of picking out everything that contain numbers for processing doesnt work on 64 systems since we have filenames like *amd64 and so.

  11. [...] to me. I actually did a LOT of Googling and asking around and eventually stumbled upon this blog: http://tuxtweaks.com/2010/10/remove-...h-one-command/ which seems to have achieved what I need! I now have 34% free in /boot. One thing I noticed was [...]

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