Technology Tales

Adventures & experiences in contemporary technology

Removing redundant kernels from Ubuntu

29th October 2022

Recently, a message appear on some web servers that I have that exhorted me to upgrade to Ubuntu 22.04.1 using the do-release-upgrade command. In the interests of remaining current, I did just that to get another message, one like the following:

The upgrade needs a total of [amount of space with units] free space on disk `/boot`.
Please free at least an additional [amount of space with units] of disk space on `/boot`.
Empty your trash and remove temporary packages of former installations
using `sudo apt-get clean`.

Using sudo apt-get clean did not resolve the problem so the advice given was of no use. The actual problem was that there were too many old kernels cluttering up /boot and searching around the web provided that wisdom. What also came up was a single command for fixing the problem. However, removing the wrong kernel can trash a system so I took a more cautious approach. First, I listed the kernels to be removed and checked that they did not include the currently running one. This was done with the following command (broken up over several lines for clarity using the backslash character to denote continuation) and running uname -r found the details of the running kernel:

dpkg -l linux-{image,headers}-"[0-9]*" \

| awk '/ii/{print $2}' \

| grep -ve "$(uname -r \

| sed -r 's/-[a-z]+//')"

The dpkg command listed the installed kernels with awk, grep and sed filtering out unwanted sections of the text. The awk command takes the tabular output from dpkg and turns it into a list. The -v switch on the grep command gets the lines that do not match the search expression created by the sed command, while the -e switch makes grep look for patterns. The sed command removes all letters from the output of the uname command, where the -r switch produces the kernel release details, to leave on the release number of the current kernel. On being satisfied that nothing untoward would happen, the full command below (also broken up over several lines for clarity using the backslash character to denote continuation) could be executed.

sudo apt purge $(dpkg -l linux-{image,headers}-"[0-9]*" \

| awk '/ii/{print $2}' \

| grep -ve "$(uname -r \

| sed -r 's/-[a-z]+//')")

This apt to purge the unwanted kernels, thus freeing up enough space for the upgrade to continue. That happened without significant incident though there were some remediations needed on the PHP side to get the website working smoothly again.

Fixing an Ansible warning about boolean type conversion

27th October 2022

My primary use for Ansible is doing system updates using the inbuilt apt module. Recently, I updated my main system to Linux Mint 21 and a few things like Ansible stopped working. Removing instances that I had added with pip3 sorted the problem but I then ran playbooks manually only for various warning messages to appear that I had not noticed before. What follows below is one of these.

[WARNING]: The value True (type bool) in a string field was converted to u'True' (type string). If this does not look like what you expect, quote the entire value to ensure it does not change.

The message is not so clear in some ways, not least because it had me looking for a boolean value of True when it should have been yes. A search on the web revealed something about the apt module that surprised me.: the value of the upgrade parameter is a string when others like it take boolean values of yes or no. Thus, I had passed a bareword of yes when it should have been declared in quotes as “yes”. To my mind, this is an inconsistency but I have changed things anyway to get rid of the message.

Lightening of desktop background images on Linux Mint Debian Edition running in Virtualbox

22nd October 2018

After a recent upgrade to Linux Mint Debian Edition 3 in a VirtualBox virtual machine that I had running its predecessor, I began to notice that background images were being loaded with more washed out of faded colours. This happened at startup so selecting another background image worked as intended until the same thing happened to that after a system restart.

This problem is not new and has affected the Cinnamon desktop in the main Linux Mint variant (the one that is based on Ubuntu) and issuing the following command in a terminal session is a suggested solution:

gsettings set org.cinnamon.muffin background-transition fade-in

In my case, that solved the problem and desktop background image display is as it should be since I executed the above. All it took was a change to a system setting.

Trying out a new way to upgrade Linux Mint in situ while going from 17.3 to 18.1

19th March 2017

There was a time when the only recommended way to upgrade Linux Mint from one version to another was to do a fresh installation with back-ups of data and a list of the installed applications created from a special tool.

Even so, it never stopped me doing my own style of in situ upgrade though some might see that as a risky option. More often than not, that actually worked without causing major problems in a time when Linux Mint releases were more tightly tied to Ubuntu’s own six-monthly cycle.

In recent years, Linux Mint’s releases have kept in line with Ubuntu’s Long Term Support (LTS) editions instead. That means that any major change comes only every two years with minor releases in between those. The latter are delivered through Linux Mint’s Update Manager so the process is a simple one to implement. Still, upgrades are not forced on you so it is left to your discretion as to when you need to upgrade since all main and interim versions get the same extended level of support. In fact, the recommendation is not to upgrade at all unless something is broken on your own installation.

For a number of reasons, I stuck with that advice by sticking on my main machine with Linux Mint 17.3 instead of upgrading to Linux Mint 18. The fact that I broke things on another machine using an older method of upgrading provided even more encouragement.

However, I subsequently discovered another means of upgrading between major versions of Linux Mint that had some endorsement from the project. There still are warnings about testing a live DVD version of Linux Mint on your PC first and backing up your data beforehand. Another task is ensuring that you are upgraded from a fully up to data Linux Mint 17.3 installation.

When you are ready, you can install mintupgrade using the following command:

sudo apt-get install mintupgrade

When that is installed, there is a sequence of tasks that you need to do. The first of these is to simulate an upgrade to test for the appearance of untoward messages and resolve them. Repeating any checking until all is well gets a recommendation. The command is as follows:

mintupgrade check

Once you are happy that the system is ready, the next step is to download the updated packages so they are on your machine ahead of their installation. Only then should you begin the upgrade process. The two commands that you need to execute are below:

mintupgrade download
mintupgrade upgrade

Once these have completed, you can restart your system. In my case the whole process worked well with only my PHP installation needing attention. A clash between different versions of the scripting interpretor was addressed by removing the older one since PHP 7 is best kept for sake of testing. Beyond that, a reinstallation of VMware Player and the move from version 18 to version 18.1, there hardly was anything more to do and there was next to no real disruption. That is just as well since I depend heavily on my main PC these days. The backup option of a full installation would have left me clearing up things for a few days afterwards since I use a bespoke selection of software.

Compressing a VirtualBox VDI file for a Linux guest

6th June 2016

In a previous posting, I talked about compressing a virtual hard disk for a Windows guest system running in VirtualBox on a Linux system. Since then, I have needed to do the same for a Linux guest following some housekeeping. The Linux distribution used is Debian so the instructions are relevant to that and maybe its derivatives such as Ubuntu, Linux Mint and their kind.

While there are other alternatives like dd, I am going to stick with a utility named zerofree to overwrite the newly freed up disk space with zeroes to aid compression later on in the process for this and the first step is to install it using the following command:

apt-get install zerofree

Once that has been completed, the next step is to unmount the relevant disk partition. Luckily for me, what I needed to compress was an area that I reserved for synchronisation with Dropbox. If it was the root area where the operating system files are kept, a live distro would be needed instead. In any event, the required command takes the following form with the mount point being whatever it is on your system (/home, for instance):

sudo umount [mount point]

With the disk partition unmounted, zerofree can be run by issuing a command that looks like this:

zerofree -v /dev/sdxN

Above, the -v switch tells zerofree to display its progress and a continually updating percentage count tells you how it is going. The /dev/sdxN piece is generic with the x corresponding to the letter assigned to the disk on which the partition resides (a, b, c or whatever) and the N is the partition number (1, 2, 3 or whatever; before GPT, the maximum was 4). Putting all this together, we get an example like /dev/sdb2.

Once, that had completed, the next step is to shut down the VM and execute a command like the following on the host Linux system ([file location/file name] needs to be replaced with whatever applies on your system):

VBoxManage modifyhd [file location/file name].vdi --compact

With the zero filling in place, there was a lot of space released when I tried this. While it would be nice for dynamic virtual disks to reduce in size automatically, I accept that there may be data integrity risks with those so the manual process will suffice for now. It has not been needed that often anyway.

A few more shell commands

8th July 2015

Here are some Linux commands that I encountered in a feature article in the current issue of Linux User & Developer that I had not met before:

cd --

This returns you to the previous directory where you were before with having to go back through the folder hierarchy to get there and is handy if you are jumping around a file system and any other means is far from speedy.

lsb_release -a

It can be useful to uncover what version of a distro you have from the command line and the above works for distros as diverse as Linux Mint, Debian, Fedora (it automatically installs in Fedora 22 if it is not installed already, a more advanced approach than showing you the command like in Linux Mint or Ubuntu), openSUSE and Manjaro. These days, the version may not change too often but it still is good to uncover what you have.

yum install fedora-upgrade

This one can be run either with sudo or in a root session started with su and it is specific to Fedora. The command performs an upgrade of the Fedora distro itself and I wonder if the functionality has been ported to the dnf command that has taken over from yum. My experiences with that in Fedora 22 so far suggest that it should be the case though I need to check that further with the VirtualBox VM that I have created.

Installing FreeBSD in a VirtualBox Virtual Machine

2nd March 2014

With UNIX being the basis of Linux, I have a soft spot for trying out any UNIX that can be installed on a PC. For a while, I had OpenSolaris on the go and even vaguely recall having a look at one of the BSD’s. However, any recent attempt to install one of the latter, and there are quite a few around now, got stymied by some sort of kernel panic caused by using AMD CPU’s. With the return to the Intel fold arising from the upgrade of my main home PC last year, it perhaps was time to try again.

The recent release of FreeBSD 10.0 was the cue and I downloaded a DVD image for a test installation in a VirtualBox virtual machine with 4 GB of memory and a 32 GB virtual hard drive attached (expanding storage was chosen so not all the allocated space has been taken so far). The variant of FreeBSD chosen was the 64-bit x86 one and I set to installing it in there. Though not as pretty in appearance as those in various Linux distros, the installer was not that user unfriendly to me. Mind you, I have experience of installing Arch Linux so that might have acclimatised me somewhat.

Those installation screens ask about the keyboard mapping that you want and I successfully chose one of the UK options. There was limited opportunity for adding extras though there was a short list of few from which I made some selections. User account set up also was on offer and I would have been better off knowing what groups to assign for my personal user account so as to have to avoid needing to log in as root so often following system start up later. Otherwise, all the default options were sufficient.

When the installation process was complete, it was time to boot into the new system and all that was on offer was a command line log in session. After logging in as root, it was time to press pkg into service in order to get a desktop environment in place. The first step was to install X:

pkg install xorg

Then, it was time to install a desktop environment. While using XFCE or KDE were alternatives, I chose GNOME 2 due to familiarity and more extensive instructions on the corresponding FreeBSD handbook page. Issuing the following command added GNOME and all its helper applications:

pkg install gnome2

So that GNOME starts up at the next reboot, some extra steps are needed. The first of these is to add the following line into /etc/fstab:

proc /proc procfs rw 0 0

Then, two lines were needed in /etc/rc.conf:


The first enables the GNOME display manager and the second activates other GNOME programs that are needed for a desktop session to start. With each of these in place, I got a graphical login screen at the next boot time.

With FreeDSB being a VirtualBox Guest, it was time to consult the relevant FreeBSD manual page. Here, there are sections for a number of virtual machine tools so a search was needed to find the one for VirtualBox. VirtualBox support for FreeBSD is incomplete in that there is no installation media for BSD systems though Linux and Solaris are supported along with Windows. Therefore, it is over to the FreeBSD repositories for the required software:

pkg install virtualbox-ose-additions

Aside from the virtual machine session not capturing and releasing the mouse pointer automatically, that did everything that was needed even if it was the open source edition of the drivers and their proprietary equivalents. To resolve the mouse pointer issue, I needed to temporarily disable the GNOME desktop session in /etc/rc.conf to drop down to a console only session where xorg. conf could be generated using the following commands:

Xorg -configure
cp /etc/xorg.conf

In the new xorg.conf file, the mouse section needs to be as follows:

Section “InputDevice”
Identifier  “Mouse0”
Driver      “vboxmouse”

If it doesn’t look like the above and it wasn’t the case for me then it needs changing. Also, any extra lines from the default set up also need removing or the mouse will not function as it should. The ALT+F1 (for accessing GNOME menus) and ALT+F2 (for running commands) keyboard shortcuts then become crucial when your mouse is not working as it should and could avert a panic too; knowing that adjusting a single configuration file will fix a problem when doing so is less accessible is not a good feeling as I discovered to my own cost. The graphics settings were fine by default but here’s what you should have in case it isn’t for you:

Section “Device”
### Available Driver options are:-
### Values: <i>: integer, <f>: float, <bool>: “True”/”False”,
### <string>: “String”, <freq>: “<f> Hz/kHz/MHz”
### [arg]: arg optional
Identifier  “Card0”
Driver      “vboxvideo”
VendorName  “InnoTek Systemberatung GmbH”
BoardName   “VirtualBox Graphics Adapter”
BusID       “PCI:0:2:0”

The next step is to ensure that your HAL settings are as they should. I needed to create a file in /usr/local/etc/hal/fdi/policy called 90-vboxguest.fdi that contains the following:

<?xml version=”1.0″ encoding=”utf-8″?>
# Sun VirtualBox
# Hal driver description for the vboxmouse driver
# $Id: chapter.xml,v 1.33 2012-03-17 04:53:52 eadler Exp $
Copyright (C) 2008-2009 Sun Microsystems, Inc.
This file is part of VirtualBox Open Source Edition (OSE, as
available from This file is free software;
you can redistribute it and/or modify it under the terms of the GNU
General Public License (GPL) as published by the Free Software
Foundation, in version 2 as it comes in the “COPYING” file of the
VirtualBox OSE distribution. VirtualBox OSE is distributed in the
hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa
Clara, CA 95054 USA or visit if you need
additional information or have any questions.
<deviceinfo version=”0.2″>
<match key=”info.subsystem” string=”pci”>
<match key=”info.product” string=”VirtualBox guest Service”>
<append key=”info.capabilities” type=”strlist”>input</append>
<append key=”info.capabilities” type=”strlist”>input.mouse</append>
<merge key=”input.x11_driver” type=”string”>vboxmouse</merge>
<merge key=”input.device” type=”string”>/dev/vboxguest</merge>

With all that set, it is time to ensure that the custom user account is added to the wheel and operator groups using this command:

pw user mod [user name] -G wheel operator

Executing the above as root means that the custom account can run the su command so that logging in as root at the start of a desktop session no longer is needed. That is what being in the wheel group allows and the anyone in the operator group can shut down or restart the system. Both are facilities readily available in Linux so I fancied having them in FreeBSD too.

Being able to switch to root in a terminal session meant that I could go on to add software like Firefox, Libreoffice, GIMP, EMACS, Geany, Netbeans, Banshee and so on. There may be a line of opinion that FreeBSD is a server operating system but all of these make it more than passable for serving as a desktop one too. There may be no package management GUI as such and the ones that come with GNOME do not work either but anyone familiar with command line working will get around that.

FreeBSD may be conservative but that has its place too and being able to build up a system one item at a time teaches far more than getting everything already sorted in one hit. So far, there is enough documentation to get me going and I hope to see where else things go too. So far, the OS hasn’t been that intimidating and that’s good to see.


1st March 2014

During the latter part of last year, the magazine Linux Format suffered a staff clear-out and I was left wondering why. It was as if a load of folk left at once and, even if I have seen that sort of thing happening at my current place of work, I was asking if something went wrong at Future Publishing.

What had passed me by was that the then staff of Linux Format were working on starting up their own magazine. They then went about crowdfunding the thing on Indiegogo and it only was the appearance of Linux Voice on a shelf in the Macclesfield branch of WHSmith’s that alerted me to what was happening in previous months.

It does sound risky to have an entire bunch of folk from one publisher’s magazine go off on their own and do their own variant of it, especially in these digital days when magazine publishing is not as secure as it once was. The mention of someone being held by no-compete covenant that reminded me of the mindset of where I work for a living. Quite what their old employers must make of it would make interesting reading because mine might be tempted to see me in court if I did something similar, assuming that was a possibility; I too would be bound by a covenant for six months after leaving.

As for the magazine itself, the content is good like it needs to be. There may be the occasional misspelling but articles on OwnCloud and Arch Linux installation would draw my attention along with reviews of Mageia 4 and FreeBSD 10. A lot of the old names from Linux Format appear too so there’s an air of continuity there. The design of the new upstart is less flashy than its longer standing predecessor and it will be interesting to see how they coexist.

It will take time for any new ideas to come to fruition and I wish the new magazine well. Its intentions are good in that half if profits are to go to open source software projects and articles are to be made available to all under a Creative Commons licence. First though, it needs to stay financially viable and the coming months could be interesting. The collective experience of who is behind the magazine should help though and that might stop it becoming like Walking World Ireland and Cycling World, other magazines whose appearance in newsagents is occasional. Having support from an enthusiastic community is a bonus too and there may come a time when I have to decide between Linux Voice and Linux Format as is the case with Linux Magazine and Linux User & Developer.  For what is supposed to be a niche operating system, users of Linux are not badly served when it comes to magazines.

A way to get Rigo working again in Sabayon

23rd October 2013

After having Sabayon running on a PC until it came to pieces after an attempted version upgrade, I went away from the Linux distro for a while and Linux Mint now runs on the aforementioned machine. It only was a certain curiosity that got me installing it into a virtual machine on VirtualBox to see if my command line method of keeping the system up to date was the cause or whether rolling or partially-rolling distros have a certain fragility that is not seen in their discrete release counterparts.

Recently that ran into a hitch, the Sabayon package manager Rigo failed to start up for me. After waiting to see if it sorted itself on its own, I looked into returning to those command line ways and that line of enquiry led me to a method of restoring Rigo’s functionality from Sabayon’s wiki page on the underlying Entropy. The first step was to issue a command to become root:


That needed the appropriate password and the next command issued updated Sabayon’s repositories:

equo update

Once that had done its thing, it was time to install new versions of Entropy and Rigo:

equo install entropy rigo

With that complete, it was time to exit the root session with the exit command. Then, it was time to try running Rigo and it worked as expected. Any thoughts of adding in the superseded Sulfur (Rigo’s predecessor) were banished on seeing that success.

Turning on autocompletion for the bash shell in terminal sessions

26th June 2013

At some point, I managed to lose the ability to have tab key based autocompletion on terminal sessions on my Ubuntu GNOME machine. Wanting it back had me turn to the web for an answer and I found it on a Linux Mint forum; the bash shell is so pervasive in the UNIX and Linux worlds that you can look anywhere for a fix like this.

The problem centred around the .bashrc file in my home area. It does have quite a few handy custom aliases and I must have done a foolish spring clean on the file sometime. That is the only way that I can explain how the following lines got removed:

if [ -f /etc/bash_completion ]; then
. /etc/bash_completion

What they do is look to see if /etc/bash_completion can be found on your system and to use it for tab-based autocompletion. With the lines not in .bashrc, it couldn’t happen. Others may replace bash_completion with bash.bashrc to got a fuller complement of features but I’ll stick with what I have for now.

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