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====== Ubuntu - Kernel - Delete Old Kernel Images ======

===== List all installed Linux kernel images =====

<code bash>
dpkg --list | egrep -i --color 'linux-image|linux-headers'
</code>

returns:

<code bash>
ii  linux-headers-4.15.0-70                    4.15.0-70.79                                    all          Header files related to Linux kernel version 4.15.0
ii  linux-headers-4.15.0-70-generic            4.15.0-70.79                                    amd64        Linux kernel headers for version 4.15.0 on 64 bit x86 SMP
ii  linux-headers-4.15.0-72                    4.15.0-72.81                                    all          Header files related to Linux kernel version 4.15.0
ii  linux-headers-4.15.0-72-generic            4.15.0-72.81                                    amd64        Linux kernel headers for version 4.15.0 on 64 bit x86 SMP
ii  linux-headers-generic                      4.15.0.72.74                                    amd64        Generic Linux kernel headers
rc  linux-image-4.15.0-29-generic              4.15.0-29.31                                    amd64        Signed kernel image generic
rc  linux-image-4.15.0-55-generic              4.15.0-55.60                                    amd64        Signed kernel image generic
rc  linux-image-4.15.0-58-generic              4.15.0-58.64                                    amd64        Signed kernel image generic
rc  linux-image-4.15.0-60-generic              4.15.0-60.67                                    amd64        Signed kernel image generic
rc  linux-image-4.15.0-62-generic              4.15.0-62.69                                    amd64        Signed kernel image generic
rc  linux-image-4.15.0-64-generic              4.15.0-64.73                                    amd64        Signed kernel image generic
rc  linux-image-4.15.0-65-generic              4.15.0-65.74                                    amd64        Signed kernel image generic
rc  linux-image-4.15.0-66-generic              4.15.0-66.75                                    amd64        Signed kernel image generic
rc  linux-image-4.15.0-69-generic              4.15.0-69.78                                    amd64        Signed kernel image generic
ii  linux-image-4.15.0-70-generic              4.15.0-70.79                                    amd64        Signed kernel image generic
ii  linux-image-4.15.0-72-generic              4.15.0-72.81                                    amd64        Signed kernel image generic
ii  linux-image-generic                        4.15.0.72.74                                    amd64        Generic Linux kernel image
</code>

----

===== Delete unwanted and unused kernel images =====

<code bash>
sudo apt --purge remove linux-image-3.12.0-27-generic
</code>


The **purge** removes packages and any configuration files are deleted too.

On newer system all obsolete kernels and headers should automatically be flagged as not being needed, and thus can be purged with the following single command:

<code bash>
sudo apt --purge autoremove
</code>

returns:

<code bash>
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages will be REMOVED:
  linux-headers-3.12.0-27* linux-headers-3.12.0-27-virtual*
0 upgraded, 0 newly installed, 2 to remove and 0 not upgraded.
After this operation, 64.7 MB disk space will be freed.
Do you want to continue [Y/n]? y
(Reading database ... 218493 files and directories currently installed.)
Removing linux-headers-3.12.0-27-virtual ...
Removing linux-headers-3.12.0-27 ...
</code>

----

===== Delete kernel packages in remove/deinstall state =====

<code bash>
sudo dpkg --list | grep linux-image
</code>

returns:

<code bash>
rc  linux-image-4.15.0-29-generic              4.15.0-29.31                                    amd64        Signed kernel image generic
rc  linux-image-4.15.0-55-generic              4.15.0-55.60                                    amd64        Signed kernel image generic
rc  linux-image-4.15.0-58-generic              4.15.0-58.64                                    amd64        Signed kernel image generic
rc  linux-image-4.15.0-60-generic              4.15.0-60.67                                    amd64        Signed kernel image generic
rc  linux-image-4.15.0-62-generic              4.15.0-62.69                                    amd64        Signed kernel image generic
rc  linux-image-4.15.0-64-generic              4.15.0-64.73                                    amd64        Signed kernel image generic
rc  linux-image-4.15.0-65-generic              4.15.0-65.74                                    amd64        Signed kernel image generic
rc  linux-image-4.15.0-66-generic              4.15.0-66.75                                    amd64        Signed kernel image generic
rc  linux-image-4.15.0-69-generic              4.15.0-69.78                                    amd64        Signed kernel image generic
ii  linux-image-4.15.0-70-generic              4.15.0-70.79                                    amd64        Signed kernel image generic
ii  linux-image-4.15.0-72-generic              4.15.0-72.81                                    amd64        Signed kernel image generic
ii  linux-image-generic                        4.15.0.72.74                                    amd64        Generic Linux kernel image
</code>

  * **rc**: means package is in remove/deinstall state and only config file exists.
  * **ii**: means package is in install state and it is 100% installed on the system.

----

==== Remove all linux-image packages in rc state ====

<code bash>
sudo x=$(dpkg --list | grep -i linux-image | grep ^rc| awk '{ print $2}')
sudo echo "$x"
sudo apt --purge remove $x
</code>

----

==== Recheck kernel package state ====

<code bash>
sudo dpkg --list | grep linux-image
</code>

returns:

<code bash>
ii  linux-image-4.15.0-70-generic              4.15.0-70.79                                    amd64        Signed kernel image generic
ii  linux-image-4.15.0-72-generic              4.15.0-72.81                                    amd64        Signed kernel image generic
ii  linux-image-generic                        4.15.0.72.74                                    amd64        Generic Linux kernel image
</code>

Note that all **rc** states have gone.

----

===== Deleting all old kernels easily =====

Get a list of kernels.

<code bash>
# Get kernel version.
v="$(uname -r | awk -F '-virtual' '{ print $1}')"
 
# Create ignore list to avoid deleting the running kernel.
i="linux-headers-virtual|linux-image-virtual|linux-headers-${v}|linux-image-$(uname -r)"
 
# Display the list.
echo dpkg --list | egrep -i  'linux-image|linux-headers' | awk '/ii/{ print $2}' | egrep -v "$i"
</code>

To delete it simply run it as follows:

<code bash>
v="$(uname -r | awk -F '-virtual' '{ print $1}')"
i="linux-headers-virtual|linux-image-virtual|linux-headers-${v}|linux-image-$(uname -r)"
apt --purge remove $(dpkg --list | egrep -i  'linux-image|linux-headers' | awk '/ii/{ print $2}' | egrep -v "$i")
</code>

----

===== Easy way to delete all old kernels =====

<code bash>
sudo apt-get purge $(dpkg -l linux-{image,headers}-"[0-9]*" | awk '/ii/{print $2}' | grep -ve "$(uname -r | sed -r 's/-[a-]+//')")
</code>

----

===== Simple way to delete all old kernels =====

<code bash>
sudo purge-old-kernels 
</code>