Snapshot Feature in VirtualBox

Oracle VirtualBox is a cross platform application that allows you to install one operating system on top of another.  "Snapshots" is a cool feature offered with VirtualBox.

With this feature we can save a particular state of a virtual machine and revert back to that state, if necessary. This is really helpful when experimenting. If something goes wrong we can easily switch back to a previous snapshot and avoid the need of frequent backups and restores. After reverting, the virtual machine will be exactly how it was before. It is similar to reverting back to a particular revision in a version control systems we are using when doing coding stuff.

We can create any number of snapshots, and they allow us to travel back and forth in virtual machine time. Snapshots can be deleted while a VM is running, to reclaim disk space.

Remember these as well;

• Once you ask VirtualBox to take a snapshot the virtual machine will be dim out periodically while a point in time snapshot is taken.

• To revert back to a particular snapshot you have to shut down the VM first.

sources.list file in Ubuntu

This is something I got to know recently while trying to install a new software package on Ubuntu. 

In Ubuntu, we use apt-get command line tool very often. It is, Ubuntu's Advanced Packaging Tool (apt) which performs functions such as installation of new software packages, upgrade of existing software packages, updating of the package list index, and even upgrading the entire Ubuntu system. 

sources.list file located in /etc/apt folder, is the default file which contains the details about the repositories needed when installing or upgrading the applications. When the system needs to know from where it may download the related stuff to install/upgrade it basically goes through this file.  

Repositories are servers which contain sets of packages. Ubuntu uses apt for package management. apt stores a list of repositories or software channels in this file. 

We can add a new repositories by simply adding a new line to this file. You can learn about the format of the entries in this file here. 

Once the editing stuff done, we have to do one more thing. Just to make apt aware of the changes done to sources.list, run;

sudo apt-get update

You can read further in Ubuntu help page.