Purging old Kernels in Ubuntu


This post is in the category: Tips

Random small break-fix or enlightening ideas


Ubuntu likes to cut space on my /boot partitions awfully close when using their auto-partition method at install time. I had an apt update fail once because of a full /boot partition and have been keeping an eye on them since. They frequently fill past 80%, so I clean out the old kernels when this happens. There is probably more of an automated way to do it, but this works for now.

Here is an example on a server where I received the last alert on:

[user]$ df -h
Filesystem                       Size  Used Avail Use% Mounted on
/dev/mapper/server--mc--01-root   11G  4.2G  6.2G  41% /
udev                             729M   12K  729M   1% /dev
tmpfs                            296M  264K  295M   1% /run
none                             5.0M     0  5.0M   0% /run/lock
none                             738M     0  738M   0% /run/shm
/dev/sda1                        228M  186M   31M  86% /boot

I hate the volume group name, but that’s another story. Notice the pretty full partition at the bottom. Let’s see what we have installed.

[root]$ dpkg --list | grep linux-image
ii  linux-image-3.2.0-48-generic     3.2.0-48.74                  Linux kernel image for version 3.2.0 on 64 bit x86 SMP
ii  linux-image-3.2.0-49-generic     3.2.0-49.75                  Linux kernel image for version 3.2.0 on 64 bit x86 SMP
ii  linux-image-3.2.0-51-generic     3.2.0-51.77                  Linux kernel image for version 3.2.0 on 64 bit x86 SMP
ii  linux-image-3.2.0-52-generic     3.2.0-52.78                  Linux kernel image for version 3.2.0 on 64 bit x86 SMP
ii  linux-image-3.2.0-53-generic     3.2.0-53.81                  Linux kernel image for version 3.2.0 on 64 bit x86 SMP
ii  linux-image-3.2.0-54-generic     3.2.0-54.82                  Linux kernel image for version 3.2.0 on 64 bit x86 SMP
ii  linux-image-3.2.0-55-generic     3.2.0-55.85                  Linux kernel image for version 3.2.0 on 64 bit x86 SMP
ii  linux-image-3.2.0-56-generic     3.2.0-56.86                  Linux kernel image for version 3.2.0 on 64 bit x86 SMP
ii  linux-image-server               3.2.0.56.66                  Linux kernel image on Server Equipment.

Yup, a little gratuitous if you ask me. Before I change anything, let’s see what kernel version this box is currently running.

[root]$ uname -r
3.2.0-54-generic

Looks like I haven’t rebooted for a while. I will do that now and run the same command again.

[root]$ uname -r
3.2.0-56-generic

Much better. So I’m going to leave one previous version, and remove (purge) the rest. So in my case, I’m going to run this.

[root]$ apt-get purge linux-image-3.2.0-48-generic linux-image-3.2.0-49-generic linux-image-3.2.0-51-generic linux-image-3.2.0-52-generic linux-image-3.2.0-53-generic linux-image-3.2.0-54-generic

Keep in mind that YMMV. By the time you read this, your versions will be different. Don’t copy that above command as-is!

Once those commands are ran, the kernel list looks a bit cleaner.

[root]$ dpkg --list | grep linux-image
ii  linux-image-3.2.0-55-generic     3.2.0-55.85                       Linux kernel image for version 3.2.0 on 64 bit x86 SMP
ii  linux-image-3.2.0-56-generic     3.2.0-56.86                       Linux kernel image for version 3.2.0 on 64 bit x86 SMP
ii  linux-image-server               3.2.0.56.66                       Linux kernel image on Server Equipment.

Also, our disk space is much better.

[root]$ df -h
Filesystem                       Size  Used Avail Use% Mounted on
/dev/mapper/server--mc--01-root   11G  3.3G  7.0G  32% /
udev                             729M   12K  729M   1% /dev
tmpfs                            296M  252K  295M   1% /run
none                             5.0M     0  5.0M   0% /run/lock
none                             738M     0  738M   0% /run/shm
/dev/sda1                        228M   50M  167M  23% /boot
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About Andrew Wells

I have been developing on the LAMP stack since about 2006. I run Ubuntu XFCE on my desktop and have a history of managing Ubuntu and CentOS servers. I code web applications mostly in PHP but have experience with other languages as well.

When I’m not working, I can be found working in my home lab or out snowboarding, hiking, camping, or biking depending on the season.

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