Review Activity

(System Services) When using the systemctl command, how does enabling a service differ from starting a service?

Answers will vary. Enabling a service causes it to start when the system starts. Starting the service launches the service for the current runtime.

(Linux Characteristics) How might anyone contribute improvements to a piece of free and open-source software?

Anyone might notice a need or requirement in software, create a solution to the problem, and then release the modified software. As the cycle is repeated, the software continues to improve.

(Storage Troubleshooting) You have added a partition to an existing disk by using fdisk. The partition is not displayed by the cat /proc/partitions command. What other command do you need to run?

partprobe

(Interact with Linux) What type of files will be found in the /etc directory?

Configuration files.

Why should the integrity of a file downloaded from the Internet be checked by tools such as SHA or MD5?

Files may be corrupted or changed during the download process. Checking file integrity with hashing tools identifies whether any changes have occurred.

(Storage Concepts) How might quotas help sysadmins manage storage capacity on a server?

Quotas help by better controlling how much data users are allowed to store on the system.

(Group Account Management) What command adds a user to a group?

The usermod command (usually with the -aG options).

(Help in Linux) Why might vendor websites be the best source of information about an application or service?

The vendor site probably contains the most current information to configure the application or service, provides the version history, and supplies examples of use.

(User and Group Troubleshooting) Another administrator asks you to explain the value of editing the /etc/sudoer's file with vimudo rather than traditional text editor. What is your response?

The vimudo editor confirms the syntax of the /etc/sudoers file. The file is very sensitive, and misconfiguration could prevent administrative access to the system.

(Privilege Escalation) You must delegate the shutdown -h privilege to SOMEUSER. What tool is used to modify the /etc/sudoers file, and what line must be added to that file?

The visudo command is run to edit the file. The following line is added to the file: SOMEUSER ALL=(ALL) NOPASSWD: SHUTDOWN_CMDS

(File Location) A coworker on the helpdesk team is troubleshooting an issue where a user is attempting to run a command, but the command is not executing. Your coworker needs to discover where the command executes from as part of the troubleshooting process. What command(s) can you suggest?

The where command would be useful.

(RPM Software Packages and Repositories) Why are .rpmnew files important during an upgrade?

These files maintain existing configuration file settings rather than overwriting them with vendor defaults.

(Debian Software Packages and Repositories) What are the two steps for upgrading software with apt?

Use the apt update command, and then use the apt upgrade command.

(Linux Characteristics) Compare the advantages and disadvantages of GUI and CLI environments.

CLI may be faster to work with and consume fewer resources. GUI is usually easier to work with and supports graphics-based applications.

(Software in Sandbox) True or False? The original practice, known as chroot, that predates the current method of sandboxing, is deprecated and no longer used.

False. The practice of chroot is still appropriate in many settings.

(Storage Troubleshooting) List the commands necessary to show configuration information for each of the three layers of LVM.

pvdisplay, vgdisplay, lvdisplay

(User and Group Troubleshooting) During a security audit it is discovered that a user does not have a password set. When you check the /etc/passwd file, the password field is properly populated with the x character. What file would actually display whether a password has been set for this user.

/etc/shadow

(The Linux File System) You are in the new-projects directory, which is stored in the projects directory within your home directory. What is the absolute path to the new-projects directory?

/home/USERNAME/projects/new-projects

(Linux Kernel) Where else is dmesg output found?

/var/log/dmesg

(Storage Options) You purchase two 100 GB storage disks to use in a RAID 1 mirror. Assuming the entire storage capacity of both disks is at your disposal, what is the maximum amount of data your RAID 1 array can store?

100 GB

(Linux Permissions) What octal value is used in absolute mode to set permissions at all access for all identities?

777

(Privilege Escalation) A developer at your organization needs the ability to reboot a test server, but their account's standard privileges do not permit this. The develop requests the system's root user password in order to use su to reboot the server. Is there a more secure option that aligns with the principle of least privilege?

A better option is sudo, which allows the administrator to delegate only the necessary task (in this case, rebooting the server). The root password combined with su would grant more than just the reboot privilege.

(Linux Kernel) What is a kernel module?

A kernel module is a prewritten piece of code that adds functionality beyond what's built into the kernel.

(Storage Deployment) What is a mount point?

A mount point is a directory where storage capacity is attached to the filesystem and made accessible to users.

(Memory) What is a swap partition?

A swap partition is a dedicated partition on a storage device that is used as virtual memory space.

(Special Linux Permissions) Why might a sysadmin set the sticky bit on a configuration file?

A sysadmin might do this to keep the configuration file from being accidentally deleted by another user or by the system (for example, during an upgrade).

(ACL configuration) Explain the benefit offered by ACLs compared to standard Linux permissions.

ACLs provide additional flexibility by permitting user and/or multiple groups to have different levels of access.

(User and Group Troubleshooting) List at least three reasons a user account might be locked.

An adminstrator locked the account while the user was on a leave of absence, an incorrect password was entered too many times, and password settings are misconfigured.

(User Account Management) What is the purpose of the /etc/skel directory?

Any files stored in this directory are automatically copied to the home directory of new user accounts. Profile files and other configurations can be easily set using /etc/skel.

(Linux Characteristics) Explain how distributions differ from each other.

Distributions tend to focus on addressing particular needs, such as an end-user workstation, multimedia editing, and high-performance service hosting.

(Troubleshoot in Linux) When should you escalate a problem?

Escalate a problem when you cannot solve it yourself (although it won't be good for your career if you give up too easily). You might also escalate if you do not have authorization to perform the necessary changes of if the system is under some sort of warranty.

(Localization Settings) True or false? The localectl command configures the system locale and keyboard settings as one collective setting that is aligned with the locale's specific cultural elements.

False. The keyboard layout can be configured separately and independently of the locale, allowing the wide variety of keyboard layouts to be used with different locale settings.

(Troubleshoot in Linux) True or False? Documentation should be created only at the end of the troubleshooting process.

False. The last step of the methodology is to ensure that findings, actions, and outcomes are documented, but you cannot do this effectively without existing notes. Most troubleshooting takes place within a ticket system. Ideally, a documented job ticket would be opened at the start of recording the incident.

(File Location) A senior sysadmin suggests that commands such as sed, awk, and sort are just as useful in automation as at the command-line. How might commands such as these be used in automation?

File management commands such as sed, awk, sort, cut, paste, tr, wc, printf, echo, and diff can be integrated into automation scripts to find, organize, and display information or provide configurations.

(System Service Configuration) Define some reasons to forward Linux log files to a central server.

Forwarding log files makes it easier to archive logs and easier to search or parse logs.

(System Services) What are the target names for the GUI and CLI startup options?

GUI = graphical.target and CLI = multi-user.target

(Software in Sandbox) What is the advantage of sandboxing?

Isolating a piece of software from any other software, the operating system, and system resources decreases its ability to damage the system.

(Linux Permissions) How does the principle of least privilege help mitigate threats and mistakes?

It mitigates threats and mistakes by providing user with only the level of access required and no more. By not having more access than needed, mistakes such as accidental or malicious changes or deletions may be avoided.

(Storage Deployment) What does /dev/sdc3 specify?

It specifies the third partition (3) on the third storage disk (c).

(System Service Configuration) When would a script run if it were configured in cron with the following settings? 30 1 * * *

It would run every day at 1:30 a.m.

(User Account Management) Why might an administrator change a user's default shell?

The user may be more comfortable with a different shell than Bash, such as the Zsh or Ksh.

(Privilege Escalation) Whose password must be entered with sudo? Whose password must be entered with su?

The user's own password must be entered with sudo. The destination user's password must be entered with su.

(Software Acquisition) How can wget or curl be used to download files from the Internet in a way that a web browser cannot be used?

They can be used in an automated file download script and a browser cannot.

(Storage Options) What do the Fibre Channel and iSCSI standards provide?

They send SCSI commands to storage over network connections.

(Software Management) Why should administrators control software repository locations?

They should do this to ensure the availability of proper software versions, authorized software, and legitimate software.

(Processes) What keys are used to cause top to display resources by memory consumption or by CPU consumption?

Use M to display memory and P to display processor consumption.

(RPM Software Packages and Repositories) Why might sysadmins restrict certain software repositories?

Version and software control, access to approved software, maintain network efficiency by only downloading software once to the network and then distributing it

(Group Account Management) Suggest at least two ways to display group membership information.

View the /etc/group file, id command, group command.

(Linux Permissions) Write the command by using symbolic mode that removes the read permission from others for fileA without impacting other permissions.

chmod o-r fileA

(System Service Configuration) A sysadmin has several virtual machines that are frequently on and off the development network. The administrator complains of time synchronization problems with applications on the VMs. What time service can you suggest to help?

chrony

(File Location) You are conducting a security audit and need to document user access to log files—specifically whether any files are world-readable or whether any allow rwx access to all users. How can the find command be used in such a project, and what specific command might you use?

find /var/log -perm 400 (for world-readable access) and find /var/log -perm 777 (for rwx to all users)

(Storage Troubleshooting) When trying to save a file to a storage disk, you receive a message stating the drive is out of space. The df command indicates there is plenty of free space. What might be the issue?

inode exhaustion

(Storage Troubleshooting) What command reports real-time disk latency information?

ioping

(Storage Deployment) What command adds the XFS filesystem to /dev/sdb2?

mkfs.xfs /dev/sdb2

(File Management Commands) A user asks how to delete a directory named /projects containing 100 directories. The user does not want to delete the files individually and does not want to be prompted to confirm the deletion of each file. What is the appropriate command expression, and why?

rm -fR /projects

(User and Group Troubleshooting) List at least three scenarios where you might need records of who logged in to a Linux system.

security incident response, security audit, troubleshooting account access

(System Services) What command restarts the sshd service after a configuration change?

systemctl restart sshd

(User and Group Troubleshooting) An administrator asks you how to delegate Linux administrative privileges to a specific user. What group is used for such delegation?

the wheel group

(Troubleshoot in Linux) A user contacts you to find out why they cannot access a directory. Using the troubleshooting methodology, how would you narrow the scope of the problem?

Checking with another user in the same group who has the same level of access to the directory will allow you to determine whether the problem is widespread.

(The Linux File System) You are installing a new application on your Linux system. The documentation states that configuration files and log files will be added to your system. Where will these files likely be stored, and how does the FHS make such installations easier?

Configuration files will likely be stored in the /etc directory, and log files will likely be stored in /var/log. The FHS makes it easier for developers to automate installations since directories such as /etc and /var/log are consistent across distributions. The FHS also makes it easier for administrators to understand where such files are likely to be stored.

(Group Account Management) What is the result if an administrator forgets to add the -a option when adding a user to a group?

The user is aded to the specified group but removed from all other groups.

(Software Management) What are the software-management phases?

The phases are install, update/maintain, remove, inventory, or query information.

(Memory) Explain the concept of virtual memory.

Because both RAM and storage drives are storage locations, if the RAM fills additional storage, space can be borrowed from storage devices and information can be swapped between the two.

(Localization Settings) Where are regional time-zone files stored on Red Hat-derived systems? And Debian-derived systems?

On Red Hat-derived systems, see /user/share/zoneinfo. On Debian-derived systems, see /etc/timezone.

(RPM Software Packages and Repositories) What information might sysadmins query the RPM database to retrieve?

Package version, install date, description, vendor, file locations

(Storage Options) Why is RAID 5 fault tolerant and RAID 0 not?

RAID 5 maintains parity information about stored data that can be used to recreate data missing from any one failed disk. RAID 0 does not store parity information.

(Storage Concepts) Explain the key differences between MBR and GPT partition tables.

MBR is limited to four partitions and a maximum drive size of 2 TB, while GPT does not have such limitations.

(Help in Linux) Name three things a man page might provide a user.

Man pages provide a summary of the command's function, examples of using the command, explanation of options.

(Group Account Management) Why might a user be a member of multiple groups?

Membership in multiple groups provides access to different resources. For example, a user who is a member of both the sales group and the marketing group can be granted access to both types of resources.

(Interact with Linux) An administrator asks you to make a change to the system's configuration. Why would you need to use Vim or Nano to accomplish this task?

Most Linux configurations are stored in text files, so changing the configuration requires editing the text files.

(ACL configuration) Does the ACL structure replace standard permissions?

No, ACLs enhance the existing standard permissions structure

(Storage Concepts) Do all RAID array designs provide fault tolerance?

No, RAID 0 Disk striping does not provide fault tolerance.

(Text Files) Why are text editors more important on Linux systems than on other systems?

System settings and service configurations are stored in text files. For a sysadmin to change the server's configuration, these files must be edited. Many Linux servers do not have a GUI and therefore do not have mouse-driven, menu-based interfaces. CLI text editors are the tools sysadmins use to reconfigure systems.

(Source Code) Why is it more common to compile software with Linux than with other operating systems?

The source code is readily available in open-source environments and can be modified before compiling. In proprietary environments, the source code is not available and software is almost always precompiled.

(Interact with Linux) Explain the difference between the su and sudo commands.

The su command switches to a different user account (usually root). The user can exercise all privileges associated with that account. The sudo command allows a user to run only specific, delegated commands that normally require administrative privileges.

(Privilege Escalation) How are the su root and su - root commands different?

The su root command switches the user identity to that of root within the user profile settings of the original user.The su - root command switches the user identity to that of root with the root user's own profile settings.

(Storage Deployment) What are the three layers of an LVM deployment?

The three layers are physical volumes, volume groups, and logical volumes.

(ACL configuration) What commands are used to set ACL entries for USERA with Rex and USERB with r-- for fileA?

Run these two commands: setfacl -m u:USERA:rws fileA setfacl -m u:USERB:r fileA

(Special Linux Permissions) How would SGID benefit user when set on the /projects directory where multiple users are members of the associate group and need access to each other's files in the directory?

SGID assigned the group association files created in the /projects directory, allowing group members to have access to each other's files.

(Linux Characteristics) Why do servers tend to rely on CLI administration and desktops rely on GUI environments?

Servers attempt to dedicate all possible resources to the provided services and do not usually run end-user applications that often require a GUI. Desktop systems often run user applications that benefit from or require a graphical component.

(Linux Permissions) Interpret the results of the following command: chown -R USERA:sales dirA

Sets the dirA directory owner to USERA and the associated group to sales. The -R option causes the owner and group change to apply to all existing files and directories in dirA.

(Processes) Differentiate between stopped processes and zombie processes.

Stopped processes are terminating and releasing their resources. Zombie processes are child processes awaiting parent-process acceptance of their termination.

(Text Files) A user contacts you and wants an easier text editor to use than Vim. There is no GUI installed on the system in question. What text editor do you suggest and why?

Suggest the Nano editor. It is less confusing because it does not use modes and the common commands are displayed in the interface.

(Storage Deployment) What role does the partprobe command play in the process of adding storage?

The partprobe command checks for changes to the partition table, updating the system with any new or removed partitions.

(Source Code) What is the effect of using ./ before an executable file?

The ./ causes Bash to check the current directory for the executable instead of the normal command path.

(User Account Management) Why are user password stored in the /etc/shadow file and not the /etc/passwd file?

The /etc/passwd file can be read by all processes and there isn't secure. The /etc/shadow file can only be read by root.

(User and Group Troubleshooting) A user places sudo before a command, but the command still fails to run. What might be the cause?

The /etc/sudoers file is not configured for the user or for the command.

(File Management Commands) A user complains that they redirected the output from several commands into a text file, but the only content that appears in the file is the output from the most recent command. How would you explain to the user what happened and how to correct the problem?

The > redirector overwrites any existing content in the target file. In the future, the user should use the >> redirector to append new content to existing content in the target file.

(Software Acquisition) How might tar be used to distribute an application?

The application source code and supporting files may be bundled into a tar archive and compressed for a more efficient download.

(Debian Software Packages and Repositories) Explain the difference between the two steps in upgrading software with apt.

The apt update command updates the database of available packages, and the apt upgrade command upgrades the actual packages.

(System Service Configuration) Differentiate between the at command scheduler and the cron scheduler.

The at command is most useful for one-time commands, and cron is most useful for commands that are repeated.

(The Linux File System) A user submits a ticket regarding a file access issue. The first file, projectA.txt, had a second hard link named my-project.txt. The same data was available via either link. The user deleted the my-project.txt file, and the data was still available via projectA.txt. The second file, projectB.txt, had a sym link that pointed to the projectB.txt link. When the projectB.txt link was deleted, the data was no longer available via the sym link. The user wants to know why the first file is still available after a link deletion but the second is not.

The first file still exists, and one hard link pointing to its content remains after the other hard link was deleted. Hard links point to the actual data stored on the drive. Data always has at least one hard link. When the only hard link to the second file was deleted, the sym link was broken because sym links do not point to data, they point to hard links (that then point to data).

(Memory) Differentiate between the free and vmstat commands.

The free command displays physical memory use. The vmstat command displays virtual memory use.

(Text Files) Explain how the keyboard responds depending on which mode Vim is currently in. How do modes add to Vim's functionality?

The keyboard issues commands to Vim in some modes (Command and Execute) and manages content in Insert mode. By allowing Vim to respond differently to keystrokes, many actions and features are possible within the editor.

(Processes) Differentiate between -15 and -9 kill signals.

The kill signal -15 asks a process to gracefully exit. The kill signal -9 terminates the process ungracefully.

(File Management Commands) You have been assigned a helpdesk ticket to answer a user question. The user is attempting to rename files but cannot find the rename command. What command do you teach the user?

The mv command, and the syntax is mv {oldname} {newname}

(Processes) Differentiate between the nice and renice commands.

The nice command is used to launch new processes at a specified priority, and the renice command is used to re-prioritize running processes.

(Software Management) Why is compiling software more common with Linux systems than with other operating systems?

The open-source nature of Linux software means there is access to the source code for customization and understanding of the software.

(Text File Management) Why is it a good practice to back up a configuration file before making changes?

The original file can be put back in place if the updated file causes issues.

(Linux Kernel) What does the output of the dmesg command display?

The output contains kernel messages covering drivers, modules, parameters, and other functions, including status and error information.