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The JPG (JPEG) format is without any doubt the most popular format used to share images on the Internet. However, there are several advantages in using PDF images compared to JPG images. For one, while JPG is a raster format with lossy compression, PDF is a layout format that contains both vector and raster graphics.

In a PDF document, bookmarks can be added as a navigational tool to allow readers to locate and quickly move to particular sections in the document by clicking on bookmark links. If a PDF file is a very log document with hundreds of pages, adding properly organized bookmarks can be essential to guide users to browse the document effectively.

When you need to demonstrate your desktop activities to someone else, using a screencast (i.e., recording of desktop screen) is far more effective than a textual tutorial or a bunch of static images. For a video tutorial, sometimes you may want to record a particular area of the desktop (e.g., one GUI window), instead of the entire desktop screen. One way to create a screencast of a particular area of the desktop is by using recordMyDesktop.

When you are using a proxy, the "proxy exception list" (also known as "ignore-hosts list") is sometimes necessary. The proxy exception list basically tells an application or desktop (which uses a proxy) to not use the proxy for particular destinations or websites. The proxy exceptions are needed when you are trying to access web servers on local LAN or those with private IP addresses which are not reachable from outside.

NFS is a distributed file system protocol built on top of Sun's RPC (remote procedure call). NFS is popularly used to share directories and files in LAN network environments, and is also adopted in many Network Attached Storage (NAS) systems and cloud storage backends. In a typical NFS deployment, an NFS server exports part of its local file system as NFS shares, and one or more remote NFS clients mount and access exported shares within their own file system.

If you want to find out whether the Linux OS is running inside a virtualized environment or on a real hardware computer, there are various heuristics you can try, depending on the type of hypervisor/container used underneath. Different hypervisors and container technologies may introduce different fingerprints within their instances (e.g., processor manufacturer, special file in /proc, virtualized NIC driver name).

Newsbeuter is a command-line RSS feed reader designed to access RSS/Atom feeds in a terminal environment. Used together with a text-mode web browser such as elinks, lynx or w3m, Newsbeuter allows you to read RSS/Atom feeds without any graphical desktop environment, such as on a headless server.

When you are writing a shell script, there are cases where you need to compare two version numbers, and proceed differently depending on whether one version number is higher/lower than the other. For example, you want to check for the minimum version requirement (i.e., $version ? 1.3.0). Or you want to write a conditional statement where the condition is defined by a specific range of version numbers (e.g., 1.0.0 ? $version ? 2.3.1).

When a program or a library is packaged as a Deb or RPM package for distribution, a set of metadata files are included in the package. One of them is a "changelog" file, which records in reverse chronological order what changes occurred each time the package has been updated. So if you want to find out what changes are made to the package that you are about to install or already installed, you can view the package's changelog.

virt-manager is a popular GUI-frontend for libvirt, allowing users to create and manage guest virtual machines on libvirt-supported hypervisors such as QEMU/KVM or Xen. virt-manager can control a host-local hypervisor as well as remote host's hypervisor (over SSH), giving users a location-transparent management interface for virtual machines.

Suppose you have a text file in which you want to change multiple lines of text to something else, but without using a text editor. When it comes to finding and replacing a multi-line string pattern, Perl's regular expression based pattern matching comes in handy.

Suppose you have a list of files on a remote host, some of which already exist locally. What you want is to transfer only those files that are not found locally. If you blindly run scp with wildcard, it would fetch all remote files (existing as well as non-existing files), and overwrite existing local files. You want to avoid this.

virt-manager is a GUI-based virtual machine manager which allows you to create and manage (local or remote) virtual machines and containers via libvirt APIs. It supports multiple hypervisors such as KVM, QEMU, Xen, as well as LXC containers. While virt-manager is available in most distros' base repositories, the pre-built virt-manager package always falls behind the latest releases available from the official website.

While CentOS/RHEL platforms maintain several official repositories (e.g., base, updates, contrib), they are lacking in terms of software coverage and release cycles. To bridge the gap between what is available and what is commonly needed, third-party repositories are created to serve community needs for commonly requested software packages.

When there are multiple kernels installed on CentOS, GRUB/GRUB2 boot loader chooses and loads one of them as the default kernel during boot time. The default kernel can be chosen differently. For example, CentOS can be configured to boot into the newest kernel installed (e.g., CentOS 6), or it can boot a last saved entry regardless of the kernel is newer or older (e.g., CentOS 7).

When you run a guest virtual machine (VM) on a hypervisor, you create one or more disk images dedicated to the VM. As a "virtual" disk volume, a disk image represents the content and structure of a storage device (e.g., a hard disk drive or flash drive) attached to the VM. If you want to modify files in a VM's disk image without powering on the VM, you could "mount" the disk image. You then would be able to modify the content of the disk image before unmounting it.

There are cases where you want to temporarily back up file permissions alone (not files themselves). For example, you want to prevent the content of some directory from being overwritten, so you temporarily remove write permission on all the files under the directory. Or you are troubleshooting file permission issues, and so running chmod on files here and there.

When you create an LXC container, it will have the default username/password set up. The default username/password will vary depending on which LXC template was used to create the container. For example, Debian LXC will have the default username/password set to root/root. Fedora LXC will have the root password set as expired, so it can be set on the first login.

When you power up your Ubuntu/Mint desktop and the boot procedure gets started in the background, you see a nice graphical animation appear in the screen. This initial bootscreen is rendered by software called Plymouth, which uses the kernel's Direct Rendering Manager (DRM) and Kernel Mode Setting (KMS) driver.

The biggest advantage of LVM over traditional disk partitions is its support for "dynamic partitions"; you can create and resize (grow or shrink) LVM volumes dynamically as needed. There is no notion of physical disk boundary in LVM logical volumes, so you can create a large LVM volume that spans across multiple smaller physical disks.