Adventures & experiences in contemporary technology
Due to a need to access websites with country blocking, I have decided to give CyberGhost a go and it also will come in handy when connecting devices to other Wi-Fi connections. What I have got is the three year subscription package and all went went well on the first day of use. However, things became unusable on the second and a reboot did not sort it.
The problem seemed to affect a phone running Android too and I even got to suspecting my router an broadband provider. Even terminating the subscription came to mind but it did not come to that. Instead, I did a bit more research and tried changing the maximum transition unit (MTU) for the connection to 1300 as suggested in a CyberGhost help article. Using the Control Panel meant that it was resetting to 1500 on my Windows 10 machine so I then turned to a command line based solution.
To do that, I started PowerShell in administrator mode from the context menu produced by right clicking on the Start Menu icon on the taskbar. Then, I entered the following command to see what connections I had and what the MTU settings were:
netsh interface ipv4 show subinterfaces
From looking through the Settings and Control Panel applications, I already had worked out what network interface belonged to the CyberGhost connection. Seeing that the MTU setting was 1500, I then issued a command like the following to change that to 1300.
netsh interface ipv4 set subinterface "<name of ethernet interface>" mtu=1300 store=persistent
Here, <name of ethernet interface> gets replace by the name of your connection and the string is quoted to avoid spaces in the name causing problems with executing the command. Once that second command had been run, the first one was issued again and the output checked to ensure that the MTU setting was as expected.
This was done when the VPN connection was inactive but it may work also with an active connection. After making the change, I again reconnected to the VPN and all has been as expected since then and I found a better connection for my Android phone too.
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.
Having seen Linux Format cover tools like Vagrant and Puppet that manage virtual machines, I have been attracted by the prospect of a virtual web server running on my own PC. Certainly, having the LAMP software stack in a VM means that the corresponding tools don’t need to be added to a host system should its operating system need a fresh installation.
As intriguing as tools like Vagrant may be, I decided that I needed to learn a bit more about getting server instances set up in VirtualBox anyway. Thus, I went and downloaded the latest version of Ubuntu Server and gave that a go. One lesson that I learned was that Bridged Networking needs to be added to the VM before installation of the operating system unless you fancy overcoming the challenge of getting Ubuntu Server to recognise an altered or additional network interface. In my case, I added an extra adapter for the Bridged Networking and left the original in place as NAT. The reason for having Bridged Networking set up is that it allows access to the virtual web server from the host once you know the IP address and that information can be obtained by executing the ifconfig command on the virtual machine.
With the networking sorted, the next step was to install the 64-bit edition of Ubuntu Server. Unlike its desktop counterpart, this is all driven by text menus but remains fairly intuitive and there is hardly anything there that you wouldn’t see with another Linux distribution. A useful addition is the addition of a menu to select the type of server services that you’d like to see installed. From this, I chose the web server and SSH options and I seem to remember that there was a database server option too. If there was an FTP server option, I would have chosen that too but it was no ordeal to add ProFTPd later on anyway.
All of this set was done through the VirtualBox GUI just to keep life more straightforward. Even so, I only selected 12 MB of video memory and was tempted to cut the overall memory back from 512 MB but leaving things be for now. However, what I have begun to do is start and stop the virtual machine from the command line since servers are headless operations anyway. With SSH enabled, there is little need to have the VirtualBox GUI going. The command for starting the server is below:
VBoxManage startvm "Ubuntu Server" --type=headless
There is a VBoxHeadless command for the same end too but VBoxManage does what I need. The startvm option is what tells VBoxManage to start the server and the virtual machine’s name is enclosed in quotes. The --type=headless ensures that no window pops up. To stop the virtual web server cleanly, a command like the following is needed:
VBoxManage controlvm "Ubuntu Server" acpipowerbutton
Again, the VBoxManage command gets used and the acpipowerbutton option ensures that a clean shutdown is performed. Not doing so results in the server not fully starting up according to my experiences thus far. Getting the virtual web server to start and stop with the host machine itself starting and stopping but this looks more complex so I plan to leave things a while before trying that experiment.