Tag Archive Debian

Creating a VirtualBox virtual disk image using the Linux command line

September 9th, 2019

Much of the past weekend was spent getting a working Debian 10 installation up and running in a VirtualBox virtual machine. Because I chose the Cinnamon desktop environment, the process was not as smooth as I would have liked so a minimal installation was performed before I started to embellish as I liked. Along the way, I got to wondering if I could create virtual hard drives using the command line and I found that something like the following did what was needed:

VBoxManage createmedium disk --filename <full path including file name without extension> -size <size in MiB> --format VDI --variant Standard

Most of the options are self-explanatory part from the one named variant. This defines whether the VDI file expands to the maximum size specified using the size parameter or is reserved with the size defined in that parameter. Two VDI files were created in this way and I used these to replace their Debian 8 predecessors and even to save a bit of space too. If you want, you can find out more in the user documentation but this post hopefully gets you started anyway.

Upgrading from OpenMediaVault 3.x to OpenMediaVault 4.x

October 29th, 2018

Having an older PC to upgrade, I decided to install OpenMediaVault on there a few years ago after adding in 6 TB and 4 TB hard drives for storage, a Gigabit network card to speed up backups and a new BeQuiet! power supply to make it quieter. It has been working smoothly since then and the release of OpenMediaVault 4.x had me wondering how to move to it.

Usefully, I enabled an SSH service for remote logins and set up an account on there for anything that I needed to do. This includes upgrades, taking backups of what is on my NAS drives and even shutting down the machine when I am done with what I need to do on there.

Using an SSH session, the first step was to switch to the administrator account and issue the following command to ensure that my OpenMediaVault 1.x installation was as up to date as it could be:

omv-update

Once that had completed what it needed to do, the next step was to do the upgrade itself with the following command:

omv-release-upgrade

With that complete, it was time to reboot the system and I fired up the web administration interface and spotted a kernel update that I applied. Again the system was restarted and further updates were noticed and these were applied, again through the web interface. The whole thing is based on Debian 9.x but I am not complaining since it quietly does exactly what I need of it.

Halting constant disk activity on a WD My Cloud NAS

June 6th, 2018

Recently, I noticed that the disk in my WD My Cloud NAS was active all the time so it reminded me of another time when this happened. Then, I needed to activate the SSH service on the device and log in as root with the password welc0me. That default password was changed before doing anything else. Since the device runs on Debian Linux, that was a simple case of using the passwd command and following the prompts. One word of caution is in order since only root can be used for SSH connections to a WD My Cloud NAS and any other user that you set up will not have these privileges.

The cause of all the activity was two services: wdmcserverd and wdphotodbmergerd. One way to halt their actions is to stop the services using these commands:

/etc/init.d/wdmcserverd stop
/etc/init.d/wdphotodbmergerd stop

The above act only works until the next system restart so these command should make for a more persistent disabling of the culprits:

update-rc.d -f wdmcserverd remove
update-rc.d -f wdphotodbmergerd remove

If all else fails, removing executable privileges from the normally executable files that the services need will work and it is a solution that I have tried with success between system updates:

cd /etc/init.d
chmod 644 wdmcserverd
reboot

Between all of these, it should be possible to have you WD My Cloud NAS go into power saving mode as it should though turning off additional services such as DLNA may be what some need to do. Having turned off these already, I only needed to disable the photo thumbnail services that were the cause of my machine’s troubles.

Compressing a VirtualBox VDI file for a Linux guest

June 6th, 2016

In a previous posting, I have 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 completed, the next step is 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 being 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

July 8th, 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.