Let's break the code one by one (for my system):
$ dpkg -l 'linux-image-*'
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description
+++-=============================-===================-===================-================================================================
un linux-image-3.0 <none> <none> (no description available)
ii linux-image-3.13.0-32-generic 3.13.0-32.57 amd64 Linux kernel image for version 3.13.0 on 64 bit x86 SMP
ii linux-image-extra-3.13.0-32-g 3.13.0-32.57 amd64 Linux kernel extra modules for version 3.13.0 on 64 bit x86 SMP
ii linux-image-generic 3.13.0.32.38 amd64 Generic Linux kernel image
$ dpkg -l 'linux-image-*' | sed '/^ii/!d'
ii linux-image-3.13.0-32-generic 3.13.0-32.57 amd64 Linux kernel image for version 3.13.0 on 64 bit x86 SMP
ii linux-image-extra-3.13.0-32-generic 3.13.0-32.57 amd64 Linux kernel extra modules for version 3.13.0 on 64 bit x86 SMP
ii linux-image-generic 3.13.0.32.38 amd64 Generic Linux kernel image
$ uname -r | sed 's/\(.*\)-\([^0-9]\+\)/\1/'
3.13.0-32
$ dpkg -l 'linux-image-*' | sed '/^ii/!d' | sed "/$(uname -r | sed 's/\(.*\)-\([^0-9]\+\)/\1/')/d"
ii linux-image-generic 3.13.0.32.38 amd64 Generic Linux kernel image
$ dpkg -l 'linux-image-*' | sed '/^ii/!d' | sed "/$(uname -r | sed 's/\(.*\)-\([^0-9]\+\)/\1/')/d" | sed 's/^[^ ]* [^ ]* \([^ ]*\).*/\1/'
linux-image-generic
$ dpkg -l 'linux-image-*' | sed '/^ii/!d' | sed "/$(uname -r | sed 's/\(.*\)-\([^0-9]\+\)/\1/')/d" | sed 's/^[^ ]* [^ ]* \([^ ]*\).*/\1/' | sed '/[0-9]/!d'
## No output
So this would do nothing:
$ sudo apt-get remove --purge $(dpkg -l 'linux-image-*' | sed '/^ii/!d;/'"$(uname -r | sed "s/\(.*\)-\([^0-9]\+\)/\1/")"'/d;s/^[^ ]* [^ ]* \([^ ]*\).*/\1/;/[0-9]/!d')
As you can see it was very close to removing my current kernel meta package linux-image-generic 3.13.0.32.38 amd64 Generic Linux kernel image
(thanks to this last sed '/[0-9]/!d'
line) , which is wrong.
In a nutshell, this piece of sed
has several issues. You should avoid it to remove your older kernels.
EDIT:
I have already said that the sed
command has issues. For the sake of extension i am going to remove the last two lines with the form that actually should be working in my current scenario.
The last two lines in a modified form:
sed -r 's/^[^ ]* *(([a-z]|-)*)(-[a-z]*) *(([0-9]|-)*)\..*/\1-\4\3/'
So:
$ dpkg -l 'linux-image-*' | sed '/^ii/!d;/'"$(uname -r |
sed "s/\(.*\)-\([^0-9]\+\)/\1/")"'/d' |
sed -r 's/^[^ ]* *(([a-z]|-)*(-[a-z]*) *(([0-9]|\.|-)*)\..*/\1\-\4\3/'
Outpus:
linux-image-3.13.0.32-generic
Thats very dengerous!!
Now showing what this would do to my system, --dry-run
ning the full apt-get remove
command:
$ sudo apt-get remove --dry-run $(dpkg -l 'linux-image-*' |
sed '/^ii/!d;/'"$(uname -r | sed "s/\(.*\)-\([^0-9]\+\)/\1/")"'/d' |
sed -r 's/^[^ ]* *(([a-z]|-)*)(-[a-z]*) *(([0-9]|\.|-)*)\..*/\1\-\4\3/')
Reading package lists... Done
Building dependency tree
Reading state information... Done
Note, selecting 'linux-image-3.13.0-32-generic' for regex 'linux-image-3.13.0.32-generic'
The following package was automatically installed and is no longer required:
linux-headers-generic
Use 'apt-get autoremove' to remove it.
The following packages will be REMOVED:
linux-generic linux-image-3.13.0-32-generic
linux-image-extra-3.13.0-32-generic linux-image-generic
0 upgraded, 0 newly installed, 4 to remove and 0 not upgraded.
Remv linux-generic [3.13.0.32.38]
Remv linux-image-generic [3.13.0.32.38]
Remv linux-image-extra-3.13.0-32-generic [3.13.0-32.57]
Remv linux-image-3.13.0-32-generic [3.13.0-32.57]
As you see it will remove all my current kernels, also note that this is just a simulation to match my current scenario and the original sed
can be improved.
** Note that the actual code will work if do a reboot
after kernel upgrade as Oli already mentioned.
EDIT2:
Here is a simple yet robust script that will consider all situations and remove the actual older kernels:
#!/bin/bash
kernels=( $(grep -Po "^linux-image-[^-]+-[^-]+-generic\b" < <(dpkg --get-selections)) )
cur_rel=$(grep -Po ".*(?=-[a-z]*$)" < <(uname -r))
for kernel in "${kernels[@]}"; do
ker_rel=$(grep -Po "[0-9].*(?=-[a-z]*)" <<< "$kernel")
dpkg --compare-versions "$ker_rel" gt "$cur_rel" && { echo "Please Restart your computer first"; break; }
dpkg --compare-versions "$ker_rel" lt "$cur_rel" && sudo apt-get remove "$kernel"
done
If you have any version that is newer than the current one this will give you a warning to restart you computer first. Also note that the older kernels are preserved due to a good reason which is if you somehow mess up your current kernel making your system unstable then you should be able to boot into any older kernel.
dpkg -l 'linux-image-*'
, which lists all installed kernel packages and filters some of them out for deletion byapt-get remove
.update-grub
(package postinst) slower. If you're worried that you didn't actually boot the kernel you were trying to upgrade to, then rununame -a
, or evendmesg | less