101-500 Practice Questions

 When using rpm --verify to check files created during the installation of RPM packages, the following information is taken into consideration:

Timestamps. RPM compares the modification time of the installed files with the original time stored in the RPM database. If the file has been modified after installation, the timestamp will differ and RPM will report it with an M flag1.

MD5 checksums. RPM calculates the MD5 checksum of the installed files and compares it with the original checksum stored in the RPM database. If the file has been altered in any way, the checksum will differ and RPM will report it with an 5 flag1.

File sizes. RPM compares the size of the installed files with the original size stored in the RPM database. If the file has been truncated or appended, the size will differ and RPM will report it with an S flag1.

RPM does not take into consideration the following information:

Inodes. RPM does not check the inode number of the installed files, as it is not a reliable indicator of file identity. The inode number can change if the file is moved, copied, or restored from a backup2.

GnuPG signatures. RPM does not verify the GnuPG signatures of the installed files, as they are not part of the RPM package format. The GnuPG signatures are used to verify the authenticity and integrity of the RPM package files before installation, not after3.

 The Logical Volume Manager (LVM) is a tool that allows the creation and management of logical volumes on Linux systems. Logical volumes are partitions that can span multiple physical disks and can be resized or deleted without affecting the rest of the system. Some of the benefits of using LVM are:

To dynamically change the size of logical volumes. LVM allows the user to increase or decrease the size of a logical volume without having to repartition the disk or reboot the system. This can be useful for allocating more space to a volume that is running out of space, or freeing up space from a volume that is not needed anymore.

To create snapshots. LVM allows the user to create a snapshot of a logical volume, which is a copy of the volume at a certain point in time. Snapshots can be used for backup purposes, as they can be restored to the original volume if needed. Snapshots can also be used for testing purposes, as they can be mounted as read-only or read-write volumes without affecting the original volume.

To dynamically create or delete logical volumes. LVM allows the user to create or delete logical volumes on the fly, without having to repartition the disk or reboot the system. This can be useful for creating temporary volumes for specific purposes, or deleting volumes that are no longer needed.

LVM cannot be used for the following purposes:

To create RAID 9 arrays. RAID 9 is not a valid RAID level, and LVM does not support RAID functionality. RAID is a technique that uses multiple disks to provide redundancy, performance, or both. RAID can be implemented at the hardware level, by using a RAID controller, or at the software level, by using tools such as mdadm or dmraid. LVM can work on top of RAID devices, but it cannot create them.

To encrypt logical volumes. LVM does not provide encryption functionality. Encryption is a technique that protects data from unauthorized access by using a secret key to transform the data into an unreadable form. Encryption can be implemented at the disk level, by using tools such as dm-crypt or LUKS, or at the file system level, by using tools such as eCryptfs or EncFS. LVM can work on top of encrypted devices, but it cannot encrypt them.

systemd, Upstart, and SysV init are all init systems used within Linux systems. An init system is the first process executed by the kernel at boot time, which has a process ID (PID) of 1, and is responsible for starting and managing all other processes on the system. Different init systems have different features, advantages, and disadvantages. Some of the most common init systems are:

systemd: A relatively new and modern init system that aims to provide a unified and efficient way of managing system and service states. It is compatible with SysV and LSB init scripts, and supports features such as parallel processing, socket activation, logging, job scheduling, and more. It is the default init system for many popular Linux distributions, such as Fedora, Debian, Ubuntu, Arch Linux, and others12.

Upstart: An event-based init system developed by Ubuntu as a replacement for SysV init. It starts and stops system tasks and processes based on events, such as hardware changes, network availability, filesystem mounting, etc. It is a hybrid init system that uses both SysV and systemd scripts, and supports features such as parallel processing, dependency tracking, logging, and more. It is the default init system for some older versions of Ubuntu, and some other Linux distributions, such as Linux Mint and Chrome OS12.

SysV init: A mature and traditional init system that follows the System V (SysV) design of Unix operating systems. It uses a series of runlevels to define the state of the system, and executes scripts in the /etc/rc.d or /etc/init.d directories according to the current runlevel. It is simple and stable, but lacks some features of modern init systems, such as parallel processing, event handling, dependency tracking, etc. It is still used by some Linux distributions, such as Slackware, Gentoo, and others12.