Installation

  • Fiber-optic cables use optical fibers to carry digital data signals in the form of modulated pulses of light.
  • Enhanced Capabilities Port (ECP) is a high-speed parallel port developed by Hewlett-Packard and Microsoft in 1992. It offers improved performance for the parallel port and requires special hardware logic. ECP ports support high throughput communications.
  • It is recommended to verify the hardware on the Linux hardware compatibility list before installing the operating system on a computer.
  • The BNC connectors are required to join the network interface card in the computer with the coaxial network cable.
  • Before installing Linux on a new computer, it is recommended to verify that each device is listed in the Hardware Compatibility List (HCL).
  • An Error Correcting Code (ECC) memory module detects and corrects single-bit errors in memory.
  • To get a glimpse of the CompTIA Linux+ certification PrepKit, you can download its free demo version (which contains 15 free practice questions) from uCertify’s web site. Click the link below:

  • The MKFS command is used to build a file system on a storage media such as a hard disk, floppy disk, etc.
  • In Linux, the first IDE drive is mounted as /dev/hda and the second one as /dev/hdb. Similarly, the first partition of the first hard disk is represented as /dev/hda1 and so on.
  • As data travels in fiber-optic cables as a light source, it can be affected by chromatic dispersion and attenuation.
  • Network File System (NFS) is used to configure file servers on a network, so that users can store data in a central location.
  • The File Transfer Protocol (FTP) command is used to update, delete, rename, move, and copy files to a server.
  • The FTP command is mostly used to distribute files over the Internet. In Linux, the FTP command requires the FTPD daemon that is started by INETD by default.
  • The SNDCONFIG command is used to configure a sound card on a Linux computer. It automatically detects a plug-and-play sound card.
  • X is often referred to as “X Windows” even though its proper name is “X”. It runs a graphical interface for a user in the same way as Microsoft Windows products do, but X can run sessions on remote computers. The configuration file of X is placed at etc/x11/xf86config.
  • GNOME and KDE provide graphical desktop environment for Linux computers, which require the graphics card for display.
  • The sound card normally uses a DMA channel. Direct Memory Access (DMA) is a technique that some components and devices use to transfer data directly to and from memory without passing through the Central Processing Unit (CPU).
  • The three primary protocols that are used for configuring e-mail setup on the Internet are POP3, IMAP, and SMTP.
  • The Xfree86 service is an implementation of the X Windows system. It is installed by default when a workstation installation is selected in Linux. It provides a graphical user interface to the users.
  • For host name to IP address mapping, the DNS service is required to be installed on a Linux server.
  • While using the FDISK utility, the p option is used to view all the existing partitions on a hard disk.
  • The /home and /var file systems are used to store users’ data and log files respectively.
  • The Linux kernel uses a swap partition to store memory data when the computer runs out of RAM.
  • Swap partition is placed on the hard disk drive of a computer. It can be a primary or a logical partition. Multiple swap partitions can be placed on a single hard disk drive.
  • FIPS is a third-party utility that can be used to modify the existing partition without losing the data in the disk drive.
  • The partition type 85 refers to the Linux extended partition.
  • The VFAT file system is compatible with the FAT file system in Windows. It is recognized by both Linux and Windows.
  • Linux Loader (LILO) is the default boot loader (boot manager) for most of the Linux systems. It is used to boot a computer into Linux.
  • The -t switch is used with the LILO command to test the changes made in the LILO configuration file. It is not used to write a new boot sector or map file, but instead it is used for tests only.
  • The error codes of LILO are used to identify the issues that have occurred during the loading of LILO.
  • When LILO loads itself, it displays the word LILO. Each letter is displayed before or after performing some specific actions. It can be used to identify issues and take further actions in case LILO fails at any point.
  • You should run /sbin/lilo to restore LILO into the MBR.
  • For a new installation, it is recommended to install LILO in the Master Boot Record (MBR). Linux provides two choices to locate LILO during installation: MBR, the first sector of the boot partition.
  • The LI error code indicates that the first stage boot loader was able to load the second stage boot loader, but it had failed to execute it. This can either be caused by a geometry mismatch or by moving /boot/boot.b without running the map installer.
  • You have made some changes in the /etc/lilo.conf file of a Linux computer. When you reboot the computer, the changes are not activated. The most likely cause of the issue is that LILO has not been executed after the changes are made in the configuration file.
  • LILO should be placed in the first sector of the boot partition if dual-booting is required, as LILO may not work with the other operating system.
  • The /etc/syslog.conf file contains the names and locations of system log files.
  • The GRUB bootloader does not require to be rewritten after the configuration of the kernel has been changed.
  • LILO uses the /etc/lilo.conf file as the default configuration file.
  • The GNU zip (GZIP) utility is a compression utility that is used to compress files for saving space.
  • RPM stands for Red Hat Package Manager. It is a command-based package management system that can be used for installing, uninstalling, querying, verifying, and updating computer software packages.
  • Using the RPM command with the -U, -v, and -h switches will upgrade the package as well as provide additional information and print hash marks during the upgrade.
  • The -q or –query switch is used with the RPM command to query the installed RPM packages.
  • The Debian Package Management System (DEB) is a package manager that is used to create installation packages from binary code.
  • To remove a package use the RPM -e command.
  • The -f switch with the RPM command is used to list the package that owns the file specified after the switch.
  • Linux uses INETD daemon to control most of the network services. INETD handles communication for these services by listening on their specific TCP/IP ports.
  • The network services in a Linux computer are configured through the /etc/inetd.conf configuration file.
  • MINICOM is a communication (dialing) program that is used to dial out from a Linux computer.
  • For a Linux server to be configured as a file and print server on the network, the hard disk drive (HDD) is the most important factor to be considered by an administrator. As the file and print server mostly serves users for keeping their files and print queues, it requires lots of storage space.

Management

  • The /proc file system is a virtual file system of the Linux operating system. It contains information about system resources.
  • If there is no free space on the hard disk drive, users will not be able to write on it. To prevent this issue from happening again, you should track the amount of free space on the hard disk.
  • The /var file system stores all variable files and temporary files created by users. It contains log files, the mail queue, the print spooler area, space for temporary storage of files downloaded from the Internet, etc.
  • The MKFS command creates the risk of destroying data on a mounted file system.
  • The FDISK command is used to obtain the summary of hard disk partitions.
  • The MKFS command is used to format a floppy disk.
  • The File System Check (FSCK) command is used to scan all disks and partitions, and it repairs them if required.
  • The FSCK command should be run only on an unmounted file system.
  • The FDISK command is used to create a partition on a new hard disk of a Linux computer.
  • The superblock is an area in a storage device of a Linux computer. It stores various bits of information about a file system, such as a pointer to the free blocks structure, the number of free inodes, etc.
  • The E2FSCK command is used to check the second extended file system (E2FS) of a Linux computer.
  • The -f option with the E2FSCK command is used to enforce the command to check the file system even if the file system seems clean.
  • The FDISK -l command is used to display the existing partitions on local hard drives in a Linux computer.
  • The DU command is used to summarize disk usage.
  • In Linux, the MOUNT command is used to mount and display disks, partitions, and file systems. Mounting refers to the process in which the operating system prepares the media to be read.
  • NFS provides users shared access to files and directories.
  • You can use the FILE command to display the file types of all the files in a directory at a time.
  • The FIND command is a versatile method for locating files on a filesystem.
  • A hard link is an index entry to reference a specific file. A hard link itself is not a file; it is the name-to-inode mapping contained in the directory file. Every file has at least one hard link, i.e., the filename by which it is known. As hard links are simply directory entries pointing to the same inode, any change to the inode or data is visible in each hard link. For example, if an administrator changes the permissions using one link, the permissions on other links will also get changed.
  • The CHMOD command is used to change file access permissions in Linux.
  • The CHOWN command is used to change the ownership of a file.
  • The CHMOD command is used to change or edit file/folder permissions in Linux.
  • When a set of numbers is assigned as permissions, the first number assigns permissions to the owner of the file or folder. The second number assigns permissions to the group, the third number to others.
  • The sticky bit is a part of a permission set applied to files or folders. The sticky bit prevents others from deleting files from a folder. When the sticky bit is set on a directory, only the owner or root can unlink (delete) or rename the files in that directory. Without the sticky bit, anyone who is able to write to the directory can delete or rename the files.
  • The tape archive (TAR) command combines a large number of files into a single file for archival purposes.
  • The .TAR file extensions is used with a single file that is created by the TAR command.
  • Use the TAR command with the -z option to create a compressed archive.
  • The tape archive (TAR) command combines a large number of files into a single file for archival purposes.
  • An incremental backup backs up files that have been changed or created since the last normal or incremental backup. It takes the backup of files of which the archive attribute is set.
  • Linux uses the /etc directory to store administrative configuration files.
  • The SHUTDOWN command brings a Linux server down in a secure way.
  • In Linux, the /etc/inittab file describes the processes that are started up during boot up.
  • The /etc/inittab file contains the configuration settings for several processes. It also contains settings for the actions to be performed after power failure. Administrators can specify the time period after which the server should start the shutdown process.
  • A run level is a state of a Linux system. It defines which system services are operating.
  • The INIT daemon is the parent of all processes. It creates processes from a script stored in the /etc/inittab file. INIT sets the following environment variables for all processes: path, init_version, runlevel, prelevel, and console.
  • The INIT daemon is called after the kernel is loaded.
  • The /etc/conf.modules file keeps the configuration of kernel modules.
  • The kernel daemon scans this file to determine which module is to be loaded during the booting of a Linux computer.
  • The /etc/shutdown.allow file keeps the list of account names of users that are allowed to shut down a Linux server.
  • The INIT 3 command sets the runlevel to 3. Runlevel 3 of a Linux system sets the system to multi-user mode with networking.
  • Single-user mode allows one user to log in and perform system maintenance tasks. A user is automatically logged into the computer as the root user when it boots in single-user mode.
  • The PS command reports the status of processes that are currently running on a Linux computer.
  • The -au switch with the PS command displays all processes owned by a specified user.
  • The KILLALL command terminates multiple processes that are running with the same name.
  • A high CPU time shows that a process is taking a high percentage of the processor time to run it. Such processes can be faulty processes. Faulty processes can usually be fixed by restarting the processes.
  • The NICE command is used to run a process with the desired priority level. The priority level varies from 1 to 19. Level 1 is for the highest and level 19 is for the lowest priority. By default, every process runs with the priority level 10.
  • The fiber-optic cable is immune to EMI.
  • NETSTATis a command-line utility that displays protocol-related statistics and the state of current TCP/IP connections.
  • PING is a command-line utility used to test connectivity with a host on a TCP/IP-based network.
  • TRACEROUTE is a route-tracing utility that displays the path an IP packet takes to reach its destination.
  • If the power cable runs along with the computer network cable, it is possible that radiation from the power cable, known as electromagnetic interference (EMI) , may be inducted into the computer network cable affecting the signals that pass through it.
  • The NETSTAT command gets all this networking information by reading the kernel routing tables in the memory.
  • The NETSTAT command with the -a switch produces all connections and listening ports.
  • The WHODO command is used to determine what process each user is running.
  • The VI is a visual interactive text editor that allows a user to create, modify, and store files on a Linux computer.
  • The :q! command is used to quit from the VI editor without saving.
  • The LPQ command is used to check a print queue.
  • The LPRM command is used to remove a file from a print queue.
  • The LPC command controls the operation of a line printer system.
  • The LPR command is used to print a file in a Linux print server.
  • The LPC command is used to control printers.
  • The /etc/printcap file contains definitions for the printers configured for a computer.
  • In order to assign a default lpr queue to the printer, it is required to edit the PRINTCAP file.
  • The LPSTAT command provides printer status information. It displays status information about the current classes, jobs, and printers.
  • TELNET is a command-line connectivity tool that starts terminal emulation with a remote host running the telnet server service.
  • Pass Linux+ certification exam in first attempt. Download latest exam simulation, questions, tutorial and study guide for Linux+ certification exam:

  • The secure shell (SSH) command is used to remotely connect to a Linux computer. It uses Private-Key Cryptography to encrypt the entire session. This is the preferred command to log in remotely to a computer and to execute programs on that host.
  • SSH uses Private-Key Cryptography to encrypt the entire session.
  • The secure shell (SSH) command is used to remotely connect to a Linux computer.
  • The SSH-KEYGEN command generates, manages, and converts authentication keys for Secure Shell. By using public-private keys, users will not have to provide passwords to communicate with other computers through SSH.
  • Set the PermitRootLogin parameter to no in the sshd_config file. With this setting enabled, remote root logins will be denied.
  • The YPWHICH command returns the name of the NIS server that supplies the NIS services to an NIS client.
  • ECHO $shell command is used to know the name of the current shell.
  • The ENV command is used to list the environment variables that are set on a Linux computer.
  • The DONE expression is used to terminate the WHILE loop command.
  • The USERADD command is used to create a new user account in a Linux server.
  • The skeleton directory (/etc/skel) contains files that are automatically copied to a user’s home directory when that user is added to the system.
  • The /etc/group file contains group information. This file shows which users are members of which groups.
  • The /etc/default/useradd file contains the default information for adding users. The ADDUSER command retrieves the default information from this file to create a new user.
  • The PASSWD command is used to change a specified user’s password.
  • The /etc/passwd file contains the passwords and login information of users.
  • The USERADD command is used to create a new user account.
  • The USERMOD command is used to modify a user account.
  • The USERMOD -c command is used to change the comment field of a user’s password file.
  • The GROUPADD command is used to create a new group account.
  • The REPQUOTA command with the -a switch is used to view the quotas of multiple users.
  • Quotas cannot be assigned to a directory. They are assigned to users and groups and applied to partitions.
  • EDQUOTA is a command line quota editor used to edit (or set) disk quota limits for users or groups.
  • The SENDMAIL -q7m command should be used to process mails every seven minutes.
  • In order to automate the task, the AT and CRON commands are used.
  • The CRON daemon executes the CRON jobs at a specified schedule.
  • The concatenate (CAT) command is used to display or print the contents of a file.
  • The PS command reports the status of processes that are currently running on a Linux computer.
  • The > command is used for storing the output generated by different commands. It creates a file specified to store the output. If the specified file already exists, it overwrites that file.
  • The LS command is used to list files on a Linux computer.

Configuration

  • The hosts.allow file is read first, and then the hosts.deny file. If access is granted to a service by the hosts.allow file, access is granted, and the hosts.deny file is ignored.
  • SFTP is an interactive file transfer command that performs all operations over an encrypted transport.
  • Domain Name System (DNS) is a hierarchical naming system used for locating domain names on private TCP/IP networks and the Internet. It provides a service for mapping DNS domain names to IP addresses and vice versa.
  • Samba is a software package that enables Linux clients to connect to the network resources (such as file shares and printers on a network) with the computers that use the Server Message Block (SMB) protocol.
  • Apache is a Web server based on HTTPd, a free server developed by the National Center for Supercomputing Applications (NCSA).
  • Squid is a high-performance proxy and caching server for Web clients. It supports FTP, Gopher, and HTTP data objects. Squid handles requests in a single non-blocking, I/O-driven process.
  • Sendmail is the most common mail server on the Internet. It is used to send and receive e-mails on a network. Incoming messages (e-mails) received by Sendmail are processed and stored in the /var/spool/mail directory.
  • To enable users to access information from the server through their Web browsers, you will have to configure a Web server on the network.
  • Squid supports SSL, extensive access controls, and full request logging.
  • If a Linux system is configured to use DHCP, the network configuration will be performed at the time of booting.
  • The /var/log/messages file is used by Samba to log startups and shutdowns of it. Generated errors in Samba are logged in /var/log/samba.
  • Class A address has 8-bit of IP address for network and 24-bit for host.
  • Class A IP addresses are assigned to networks with a large number of hosts. Class A allows for 126 networks and 16,777,214 hosts per network.
  • The ROUTE command is used to add route in the route table.
  • The /etc/fstab file contains a list of the file systems to be mounted automatically at startup.
  • The /etc/mtab file is used to display the status of currently-mounted file systems in a Linux computer.
  • The /etc/samba/smb.conf file is used to configure Samba.
  • The BIND DNS server is used on the vast majority of name serving machines on the Internet, providing a robust and stable architecture on top of which an organization’s naming architecture can be built.
  • Linux uses the Pump utility to assign IP addresses automatically to the client computers on a network.
  • Keeping . (dot) in a root’s path is considered to be a major security concern. A hacker can use this place to keep his own version of well-known and highly used commands, such as LS. When the root user will run that command, the changed program will run with privileges of the root user. This can be one of the greatest security risks.

Security

  • The sshd_config file is used to control the behavior of the SSH server.
  • KILL is a command used to terminate a specified process.
  • For VPN connections, Linux uses 3DES encryption.
  • If commands are behaving abnormally, the most likely cause is that the security has been compromised.
  • The switch user (SU) command is used to switch from one user login to another.
  • SUDO is a Unix/Linux-based utility that provides an efficient way to give specific users permission to use specific system commands at the root level of a Linux operating system.
  • If you do not specify any user account with the SU command, the command switches the login for the root user and prompts for the root user password. The -c switch with the SU command passes a single command to the shell. You can use the RM command with the -c option to remove the required files. The -rf switch with the RM command does not confirm the user before file deletion.
  • By default, an application runs with the privileges of the user who runs the application.
  • If an application requires superuser permission to write to other files and other users need to run it, change the application to SUID command.
  • The FIND /-perm -4000 command will search the current directory and its sub-directories for all the files on which SUID has been set.
  • SNORT is an open source network intrusion detection system. The SNORT application analyzes network traffic in realtime mode. It performs packet sniffing, packet logging, protocol analysis, and a content search to detect a variety of potential attacks. The SNORT application does not detect viruses, nor does it scan the hard disk drive.
  • IPTABLES -F deletes (or flushes) every rule in the specified chain. If no chain is specified, it deletes the rules from all chains.
  • The SUM command is used to verify that the MD5 checksum value is the same.
  • When software files are downloaded from the Internet, your first step should be to check the entirety of each file. Most of the Internet sites list a checksum value for a file, which is calculated from the exact file contents. Mostly all checksum values are calculated using the MD5 algorithm.
  • The UMASK command sets initial file permissions when files are created.
  • The “x” character in the second field of the user account record of the /etc/passwd file indicates that the user account is using a shadow password.
  • The password field set to * indicates that the account is disabled.
  • The /etc/shadow file contains the shadowed password entries in Linux.
  • The PWCONV command is used to convert password entries in the /etc/passwd file to shadowed passwords.
  • The MKPASSWD command generates or assigns a random password to a user account in a Linux computer.
  • After enabling shadowed passwords in a Linux server, the passwords are stored in the /etc/shadow file.
  • TCP Wrappers authenticates a request by using the hosts.deny and hosts.allow files, and starts the required server service if the requesting client has the permission. By configuring these two files, you can protect your server from intruders who exploit services that are started with TCP Wrappers.
  • CHROOT runs a command or an interactive shell with a special root directory.
  • The W command displays currently logged-in users and their tasks.

Documentation

  • The /etc/profile file is used to set a computer-wide environment and start-up programs for all users. Each time a user logs on, the computer reads this file.
  • The TOP application is used to display a dynamic real-time view of a running system. It is used to display system summary information as well as a list of the tasks currently being managed by the Linux kernel.
  • To improve the ability to provide user support, you should create a separate directory and store instructions for using all the installed applications in it.
  • Linux Documentation Project is used to store Linux-related documentation. It offers a central source for all types of documents.
  • Information on the root password, system file locations, and shadow file location must never be made public.
  • The documentation of work performed on the Linux servers should be maintained in their respective locations in a file binder.
  • While documenting a server, you should always document the daemon configuration and performance baseline.
  • Log files store errors and warnings generated by a Linux system. In Linux, the SYSLOGD and KLOGD utilities are used for logging errors and debugging messages.
  • The /var/log directory contains the log files in Linux.
  • The time and date of user logins are written in the /var/log/wtmp file. Suspicious activities of users can be tracked down through this file.
  • The kernel and system errors are written in the /var/log/messages file. Administrators should check this file daily for warning messages.
  • The kernel and system errors are written in the /var/log/messages file. Administrators should check this file daily for warning messages.
  • The TAIL command is used to view the last few lines of the log files that store the most recent log entries.
  • The TAIL 35 /var/log/messages command will display the last thirty-five lines of the /var/log/messages log file.
  • The results of the last system boot is written in the /var/log/dmesg file. It stores kernel messages that appear during the boot stage. This file helps in tracking down the boot time problems.
  • The concatenate (CAT) command is used to display or print the contents of a file.
  • The CAT /var/log/messages | MORE command will help display the contents of the file one screen at a time.
  • The GREP command is used to search for a specific pattern of text in a file.
  • The APROPOS command is used to search the Whatis database and display the short descriptions of the specified system command.
  • The manual (MAN) pages contain the syntax, instruction, and information about programs and their options.

Hardware

  • The real time clock uses IRQ 8.
  • After installing the sound card, you restart the computer. Then you find that your another device on the computer has stopped working. This is the symptom of IRQ conflict.
  • COM2 and COM4 serial ports use IRQ 3. COM1 and COM3 serial ports use IRQ 4.
  • The memory mapped to input/output (I/O) adapters is used to specify memory address for peripherals.
  • DMA is used by a hardware device to save time by transferring data to the memory without CPU intervention.
  • Interrupt request (IRQ) is a method through which a device driver requests the microprocessor to provide service.
  • When a request occurs, the microprocessor suspends the current operation and gives control to the device driver associated with the interrupt number issued.
  • COM2 and COM4 use IRQ3 by default.
  • Media Access Control (MAC) address is a numerical identifier that is unique for each network interface card (NIC). MAC addresses are 48-bit values expressed as twelve hexadecimal digits, usually divided into hyphen-separated pairs: for example, FF-00-F8-32-13-19. A MAC address consists of two parts. The first three pairs are collectively known as the Organizationally Unique Identifier (OUI). The remaining part is known as device ID. The OUI is administered by IEEE. MAC addresses are also referred to as hardware addresses, Ethernet addresses, and universally administered addresses (UAAs).
  • The floppy disk controller uses IRQ 6 by default.
  • By default, a serial port device uses IRQ 4.
  • The COM2 port (/dev/ttyS1) uses IRQ 3 by default.
  • The first parallel port of a Linux workstation is represented by the /dev/lp0 identifier. All devices in Linux are defined in the /dev directory.
  • The /dev/sda identifier represents the first drive on the first SCSI bus.
  • In Linux, each device is represented by a file name. The first IDE hard disk drive is represented by the /hda file name. If a computer has more than one IDE drive, they are given file names /hdb, /hdc, and so on.
  • The /dev directory contains files that represent access points to the devices installed on a Linux computer. These devices include terminal devices, floppy disk drives, hard disk drives, RAM, CD-ROMs, etc.
  • IFCONFIG is a command-line tool that is used for network interface management.
  • The first ethernet interface of a Linux computer is mounted as eth0. The IFCONFIG eth0 down command will disable the first ethernet interface.
  • The IFCONFIG command with the up option activates the specified interface.
  • The lo option with the IFCONFIG command is used to view the loopback interface.
  • The /proc file system contains hardware configurations of a Linux computer.
  • While the TOP application is running, pressing the ‘N’ key sorts data according to the % memory usage of the task.
  • The down option with the IFCONFIG command is used to deactivate the specified interface.
  • Sniffers tend to hear everything, so they put interfaces in “promiscuous mode,” i.e., they hear all traffic on the LAN, not just the traffic sent their way.
  • Speed, expansion, and easy configuration of hardware devices is the prime benefits of using USB.
  • Institute of Electrical and Electronics Engineers (IEEE) 1394 supports a data transfer rate of 400Mbps.
  • Install a USB host adapter card on the motherboard to use the USB modem.
  • According to the USB 2.0 standard, the maximum cable length between devices should be 5 meters.
  • If you find that the floppy drive LED remains on continuously, the most likely cause of the issue is that the data cable is inserted backward at either the drive or the controller connection.
  • Personal Computer Memory Card International Association (PCMCIA) card is also known as PC card. The PC card uses a small expansion slot and is primarily used in laptops.
  • To enable the automatic shutdown of a Linux computer, UPS and Powerd daemon are required to be installed on the computer.
  • A CD-ROM drive commonly uses the ATAPI interface.
  • ATAPI technology is a standard for mass storage devices.
  • ATAPI is used for extending EIDE.
  • The SCSI controller uses the ID 7.
  • SCSI devices do not use IRQs. They use SCSI IDs.
  • A minimum of three disks are required for configuring disk striping with parity (RAID 5). If you want to configure a computer with a hot spare disk, at least one extra disk will be required.
  • RAID-5 volume uses the storage capacity of one hard disk for keeping the parity information of the RAID.

Download links are:

Comments are closed.