VNC (Virtual Network Computer) is a low-bandwidth cross-platform display system. VNC is a system for controlling a computer remotely and sharing desktops over a network using a graphical interface. Access to a remote desktop requires a VNC server installed on the remote system, a VNC viewer on the system from which access is being established […]
Time to live exceeded ping error
Every packet of data that is sent out includes a TTL value within the IP packet header. This refers to the number of hops data can go through before it is discarded. Based on network traffic between hosts, it is possible to predict what OS is running on a system. Every operating system has its […]
What is the difference between insmod and modprobe
During development, you usually use insmod to load a module and it should be given the path of the module to load: $ insmod filename [module-options] It is low-level form of module loading, that forms the base of other module loading methods, and is the one we will use in this book. On the other […]
Upgrading from CentOS/RHEL 7 to CentOS/RHEL 8 using Leapp
The Leapp utility is a framework for updating and upgrading operating systems as well as applications. The utility’s component packages enable the creation of different workflows into profiles for updating software. Currently, the Leapp utility is used to upgrade the operating systems only, specifically, from the current CentOS/RHEL 7 release to the current CentOS/RHEL 8 […]
What are /dev/zero and /dev/null files in Linux
“/dev/zero” and “/dev/null” are two dummy device files that are useful for creating empty files. But there is a distinct difference in what they actually do. In this post, we will see the difference between the two and where they can be used. /dev/zero file It is used to create a file with no data […]
grpck command – Remove corrupt or duplicate entries in the /etc/group and /etc/gshadow files.
The grpck command removes corrupt or duplicate entries in the /etc/group and /etc/gshadow files. It generates warnings for other errors found. grpck will prompt for a “yes” or “no” before deleting entries. If the user replies “no,” the program will exit. If run in a read-only mode, the reply to all prompts is “no.” Alternate […]
xxd command – Expressed in hexadecimal form
Similar to od, xxd produces a hexadecimal or binary dump of a file in several different formats. It can also do the reverse, converting from its hex dump format back into the original data. For example, here’s a hex dump of binary file /usr/bin/who: $ xxd /usr/bin/who 0000000: 7f45 4c46 0101 0100 0000 … 0000 […]
sesearch: command not found
The seinfo and sesearch utilities can assist users in performing single-step analysis: they either provide immediate information about a SELinux object (which is mainly what seinfo is about) or are capable of querying direct SELinux rules (which is the scope of sesearch). These utilities are provided through the setools package. Where the seinfo application displays […]
macof: command not found
MAC address flooding is a great way to render a network useless. Basically, through MAC flooding, you can turn the network into a large hub. MAC flooding works by essentially allowing the switch ports to learn as many MAC addresses as they see on their ports, and if no limits on in place, can fill […]
qemu-system-x86_64: command not found
Quick Emulator (QEMU) is the main component of the QEMU/KVM virtualization technology suit. It provides hardware virtualization and processor emulation. QEMU runs in userspace and, without the need for kernel, drivers can still provide fast system emulation. QEMU supports two operating modes: Full system emulation, where QEMU emulates an entire computer system, including the CPU […]