Adventures & experiences in contemporary technology
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.
Once you end up with Windows overwriting your master boot record (MBR), you have lost the ability to use GRUB. Therefore, it would be handy to get it back if you want to start up Linux again. Though the loss of GRUB from the MBR was a deliberate act of mine, I knew that I’d have to restore GRUB to get Linux working again.So, I have been addressing the situation with a Live DVD for the likes of Ubuntu or Linux Mint. Once one of those had loaded its copy of the distribution, issuing the following command in a terminal session gets things back again:
sudo grub-install --root-directory=/media/0d104aff-ec8c-44c8-b811-92b993823444 /dev/sda
When there were error messages, I tried this one to see if I could get more information:
sudo grub-install --root-directory=/media/0d104aff-ec8c-44c8-b811-92b993823444 /dev/sda --recheck
Also, it is possible to mount a partition on the boot drive and use that in the command to restore GRUB. Here is the required combination:
sudo mount /dev/sda1 /mnt
sudo grub-install --root-directory=/mnt /dev/sda
Either of these will get GRUB working without a hitch and they are far more snappy than downloading Boot-Repair and using that; I was doing that for a while until a feature on triple booting appeared in an issue of Linux User & Developer that reminded me of the more readily available option. Once, there was a need to manually add an entry for Windows 7 to the GRUB menu too and, with that instated, I was able to dual-boot Ubuntu and Windows using GRUB to select which one was to start for me. Since then, I have been able to dual boot Linux Mint and Windows 8.1 with GRUB finding the latter all by itself so your experiences too may show this variation so it’s worth bearing in mind.
Last week, I kept getting a multitude of messages from Ubuntu’s crash reporting tool, Apport. So many would appear at once on reaching the desktop session during system start-up that I actually downloaded an installation ISO disk image with the intention of performing a fresh installation to rid myself of the problem. In the end, it never came to that because another remedy produced the result that I needed.
Emptying /etc/crash was a start but it did not do what I needed and I disabled Apport altogether. This meant editing its configuration file, which is named apport and is found in /etc/default/. The following command should open it up in Gedit on supplying your password:
gksudo gedit /etc/default/apport
With the file opened, look for the line with enabled=1 and change this to enabled=0. Once that is done, restart Apport as follows:
sudo restart apport
This will need your account password to be supplied before it will act and any messages should appear thereafter. Of course, I would not have done this if there was a real system problem but my Ubuntu GNOME installation was and is working smoothly so it is the remedy that I needed. The idea behind the tool is that Ubuntu developers get information on any application crashes but I find that it directs me to the Ubuntu Launchpad bug reporting website and that requires a user name and password for the information to be processed. For some reason, that is enough to stall me and I wonder if there could be a way of getting developers what they need without adding that extra manual step. Then, more information gets supplied and we get a more stable operating system in return.
The progress of Windows 10 is something that I have been watching. Early signs have been promising and the most recent live event certainly contained its share of excitement. The subsequent build that was released was another step in the journey though the new Start Menu appears more of a work in progress than it did in previous builds. Keeping up with these advances sometimes steps ahead of VirtualBox support for them and I discovered that again in the last few days. VMware Player seems unaffected so I thought that I’d try a migration of the VirtualBox VM with Windows 10 onto there. In the past, I did something similar with a 32-bit instance of Windows 7 that subsequently got upgraded all the the way up to 8.1 but that may not have been as slick as the latest effort so I thought that I would share it here.
The first step was to export the virtual machine as an OVF appliance and I used File > Export Appliance… only to make a foolish choice regarding the version of OVF. The one that I picked was 2.0 and I subsequently discovered that 1.0 was the better option. The equivalent command line would look like the following (there are two dashes before the ovf10 option below):
VboxManage export [name of VM] -o [name of file].ova --ovf10
VMware have a tool for extracting virtual machines from OVF files that will generate a set of files that will work with Player and other similar products of theirs. It goes under the unsurprising name of OVF Tool and it usefully works from a command line session. When I first tried it with an OVF 2.0 files, I got the following error and it stopped doing anything as a result:
Line 2: Incorrect namespace http://schemas.dmtf.org/ovf/envelope/2 found.
The only solution was to create a version 1.0 file and use a command like the following (it’s a single line though it wraps over two here and there are two dashes before the lax switch):
ovftool --lax [name of file].ova [directory location of VM files]/[name of file].vmx
The --lax option is needed to ensure successful execution even with an OVF 1.0 file as the input. Once I had done this on my Ubuntu GNOME system, the virtual machine could be opened up on VMware Player and I could use the latest build of Windows 10 at full screen, something that was not possible with VirtualBox. This may be how I survey the various builds of the operating that appear before its final edition is launched later this year.
Being ever curious on the technology front, the release of the first build of a Technical Preview of Windows 10 was enough to get me having a look at what was on offer. The furore regarding Windows 8.x added to the interest so I went to the download page to get a 64-bit installation ISO image.
That got installed into a fresh VirtualBox virtual machine and the process worked smoothly to give something not so far removed from Windows 8.1. However, it took until release 4.3.18 of VirtualBox before the Guest additions had caught up with the Windows prototype so I signed up for the Windows Insider program and got a 64-bit ISO image to install the Enterprise preview of Windows 10 into a VMware virtual machine since and that supported full screen display of the preview while VirtualBox caught up with it.
Of course, the most obvious development was the return of the Start Menu and it works exactly as expected too. Initially, the apparent lack of an easy way to disable App panels had me going to Classic Shell for an acceptable Start Menu. It was only later that it dawned on me that unpinning these panels would deliver to me the undistracting result that I wanted.
Another feature that attracted my interest is the new virtual desktop functionality. Here I was expecting something like what I have used on Linux and UNIX. There, each workspace is a distinct desktop with only the applications open in a given workspace showing on a panel in there. Windows does not work that way with all applications visible on the taskbar regardless of what workspace they occupy, which causes clutter. Another deficiency is not having a desktop indicator on the taskbar instead of the Task View button. On Windows 7 and 8.x, I have been a user of VirtuaWin and this still works largely in the way that I expect of it too, except for any application windows that have some persistence associated with them; the Task Manager is an example and I include some security software in the same category too.
Even so, here are some keyboard shortcuts for anyone who wants to take advantage of the Windows 10 virtual desktop feature:
Otherwise, stability is excellent for a preview of a version of Windows that is early on its road to final release. An upgrade to a whole new build went smoothly when initiated following a prompt from the operating system itself. All installed applications were retained and a new taskbar button for notifications made its appearance alongside the existing Action Centre icon. So far, I am unsure what this does and whether the Action Centre button will be replaced in the fullness of time but I am happy to await where things go with this.
All is polished up to now and there is nothing to suggest that Windows 10 will not be to 8.x what 7 was to Vista. The Start Screen has been dispatched after what has proved to be a misadventure on the part of Microsoft. The PC still is with us and touchscreen devices like tablets are augmenting it instead of replacing it for any tasks involving some sort of creation. If anything, we have seen the PC evolve with laptops perhaps becoming more like the Surface Pro, at least when it comes to hybrid devices. However, we are not as happy smudge our PC screens quite like those on phones and tablets so a return to a more keyboard and mouse centred approach for some devices is a welcome one.
What I have here are just a few observations and there is more elsewhere, including a useful article by Ed Bott on ZDNet. All in all, we are early in the process for Windows 10 and, though it looks favourable so far, I will continue to keep an eye on how it progresses. It needs to be less experimental than Windows 8.x and it certainly is less schizophrenic and should not be a major jump for users of Windows 7.
The release of CentOS 7 stoked my curiosity so I gave it a go in a VirtualBox virtual machine. It uses GNOME Shell in classic mode so the feel is not too far removed from that of GNOME 2. One thing to watch though is that it needs at least version 4.3.14 of VirtualBox or the Guest Additions kernel drivers will not compile at all. That might sound surprising when you learn that the kernel version is 3.10.x and that for GNOME Shell is 3.8.4. Much like Debian production releases, more established versions are chosen for the sake of stability and that fits in with the enterprise nature of the intended user base. Even with that more conservative approach, the results still please the eye though attempting to change the desktop background picture managed to freeze the machine. Other than that, most things work fine.
Even so, there are unexpected things to be encountered and one that I spotted was that network connectivity needed to switched on every time the VM was started. The default installation gives rise to this state of affairs and it is a known situation with CentOS from at least version 6 of the distribution and is not so hard to fix once you know what to do.
What you need to do is look for the relevant configuration file in /etc/sysconfig/network-scripts/ and update that. Using the ifconfig command, I found that the name of the network interface. Usually, this is something like eth0 but it was enp0s3 in my case so I had to look for a file named ifcfg-enp0s3 and edit that. The text that is sought is ONBOOT=no and that needs to become ONBOOT=yes for network connections to start automatically. To do something similar from the command line, CentOS had suggested the following:
sed -i -e ‘s@^ONBOOT=”no@ONBOOT=”yes@’ ifcfg-enp0s3
The above uses sed to do an inline (and case insensitve) edit of the file to change the offending no to a yes, once you have dropped in the /etc/sysconfig/network-scripts/ directory. My edit was done manually with Gedit so that works too. One thing to add is that any file editing needs superuser privileges so switching to root with the su command and using sudo is in order here.
Though I use only the command line to do system updates, I still got system restart messages every time a new kernel version was installed. While they can be helpful, I actually prefer to be left to my own devices when it comes to restarting a system and I may have a something running at the time that I do not wish to interrupt.
In Ubuntu GNOME 13.10 and before, there was no sign of these messages so I decided to see if I could go nag free again. The responsible application is called Update Notifier and I tried seeing if I could remove it but that act has a major impact of the system so it was not a useful way to go.
As it happens, it is an application that starts up automatically at computer boot time but there was no sign of an entry for it in the Startup Applications Preferences screen (started using from the command line using gnome-session-properties). The for this is that there is flag called NoDisplay in the relevant autostart shortcut in /etc/xdg/autostart/ that stops it appearing in the aforementioned settings screen when set to true. The trick then is to set it to false and the following command (broken over two lines for sake of display and quotes could need replacing when you issue the command too) does the trick for all such hidden start-up applications:
sudo sed -i ‘s/NoDisplay=true/NoDisplay=false/g’
/etc/xdg/autostart/*.desktop
What the above does is that sed goes into every file and changes NoDisplay=true to NoDisplay=false in each file with the desktop extension. When that has completed, there are more entries in Startup Applications Preferences and Update Notifier can be deselected in order to stop it starting. Removing the relevant .desktop file would be a more permanent change but this one will do me, especially since no more of those pesky restart messages appear anymore. My regularity when it came to system updates meant that the update messages never appeared anyway and I tend to shut down my system at the end of every day so the updates will be picked up too so all should be well.
There are times when you might need to drop back to a full screen terminal session from a graphical desktop environment when running Linux. One example that I have encountered is the installation of Nvidia’s own graphics drivers on either Ubuntu or Linux Mint. Another happened to me on Arch Linux when a Cinnamon desktop environment update left me without the ability to open up a terminal window. Then, the full screen command allowed me to add in an alternative terminal emulator and Tech Drive-in’s list came in handy for this. there might have been something to sort on a FreeBSD installation that needed the same treatment. This latter pair happened to me on sessions running within VirtualBox and that has its own needs when it comes to dropping into a full screen command line session and I will come to that later.
When running Linux on a physical PC, the keyboard shortcuts that you are CTRL + ALT + F1 for entering a full screen terminal session and CTRL + ALT + F7 for returning to the graphical desktop again. When you are running a Linux guest in VirtualBox and the host operating system also is Linux, then the aforementioned shortcuts do not work within the virtual machine but instead affect the host. To get the guest operating system to drop into a full screen terminal session, the keyboard shortcut you need is [Host Key] + F1 and the default host key is the right hand CTRL key on your keyboard unless you have assigned to something else as I have. The exit the full screen terminal session and return to the graphical desktop again, the keyboard shortcut is [Host Key] + F7.
All of this works with GNOME and Cinnamon desktop environments running in X sessions and I cannot vouch for anything else unless alternatives like Wayland come my way. Hopefully, this useful functionality applies to those other set-ups too because there are times when a terminal session is needed to recover from a mishap, rare though those thankfully are and they need to be very rare if not non-existent for most users.
On upgrading from Ubuntu GNOME 13.10 to Ubuntu GNOME 14.04, a few rough edges were to be noticed. One was the display of my chosen background image: it was garbled. Later, I discovered that there is a maximum width of 2560 px for background images in GNOME Shell these days and that things get messy beyond that.
In my case, the image width was around 6000 px and I was used to its getting resized in GNOME Shell 3.8 and its predecessors. It seems that the functionality got removed after that though so the workaround of manual image resizing in the GIMP needed to be employed. Though having big images open in memory creates an additional overhead, not handling them very well at all looks like a bug caused by setting 2560 px as a maximum screen width for the GNOME Shell panel and the complete removal of Nautilus from desktop rendering duties. Let’s hope that sense is seen with ever larger screen sizes and resolutions coming our way.
It’s the sort of thing that did get me looking at adding on Cinnamon 2.2 for a while before setting background image scaling using the indispensable GNOME Tweak Tool was discovered. LinuxG.net has a useful tutorial on this for anyone with such an adventurous streak in them. For now though, I am OK with my set up but the GNOME project’s focus on minimalism could affect us in other ways so I can see why Clem Lefebvre started the Cinnamon one primarily for Linux Mint and the desktop environment is appearing elsewhere too. After all, Gedit lost its menu bar in GNOME 3.12 so it’s just as well that we have alternative choices.
Update 2014-05-06: It seems that the desktop image bug that afflicts GNOME Shell 3.10 got sorted for GNOME Shell 3.12. At least, that is the impression that an Antergos instance in a VirtualBox virtual machine gives me.
When I recently did my usual system update for the stable version Ubuntu GNOME, there were some updates pertaining to apt and the process failed when I executed the following command:
sudo apt-get upgrade
Usefully, some messages were issued and here’s a flavour:
Setting up apt (0.9.9.1~ubuntu3.1) …
ERROR: Can’t find the archive-keyring
Is the ubuntu-keyring package installed?
dpkg: error processing apt (--configure):
subprocess installed post-installation script returned error exit status 1
Errors were encountered while processing:
apt
E: Sub-process /usr/bin/dpkg returned an error code (1)
Some searching on the web revealed that the problem was that there were no files in /usr/share/keyring when there should have been and I had not removed them myself so I have no idea how they disappeared. Various remedies were tried and any that needed software installed were non-starters because apt was disabled by the lack of keyring files. The workaround that restored things for me was to take a copy of the files in /usr/share/keyring from an Ubuntu GNOME 14.04 installation in a VirtualBox VM and copy them in to the same location in its Ubuntu GNOME 13.10 host. For those without such resources, I have packaged them in a zip file below. Other remedies like Y PPA also were suggested where I was reading but that software package needed installing beforehand so it was little use to me when the likes of Synaptic were disabled. If there are other remedies that do not involve an operating system re-installation, I would like to know about them too as well as possible causes for the file loss in the first place and how to avoid these.