XK0-005 CompTIA Exam Lab Questions

The error indicates that the cron user does not have permission to run the cronjob. Creating a cron.allow file and adding the user cron to it will allow that user to run cronjobs. The cron.allow file is a security feature that controls which users are allowed to use cron.

The command vmstat will most likely be run next by the administrator to troubleshoot the system performance. The vmstat command is a tool for reporting virtual memory statistics on Linux systems. The command shows information about processes, memory, paging, block IO, interrupts, and CPU activity. The command can help the administrator identify the source of the performance issue, such as high CPU usage, low free memory, excessive swapping, or disk IO bottlenecks. The command can also be used with an interval and a count to display the statistics repeatedly over time and observe the changes. The command vmstat will provide useful information for diagnosing the system performance and finding the root cause of the issue. This is the most likely command to run next after the top command. The other options are incorrect because they either do not show the virtual memory statistics (strace or lsof) or do not provide more information than the top command (htop). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 14: Managing Processes and Scheduling Tasks, page 425.

The command that will back up the directory /data and all its contents to /backup/data on a remote server named remote is rsync -a /data remote:/backup/. This command uses the rsync tool, which is a remote and local file synchronization tool. It uses an algorithm to minimize the amount of data copied by only moving the portions of files that have changed. The -a option stands for archive mode, which preserves the permissions, ownership, timestamps, and symbolic links of the files. The /data argument specifies the source directory to be backed up, and the remote:/backup/ argument specifies the destination directory on the remote server. The rsync tool will create a subdirectory named data under /backup/ on the remote server, and copy all the files and subdirectories from /data on the local server.

The other options are not correct commands for backing up a directory to a remote server. The scp -p /data remote:/backup/data command will copy the /data directory as a file named data under /backup/ on the remote server, not as a subdirectory with its contents. The -p option preserves the permissions and timestamps of the file, but not the ownership or symbolic links. The ssh -i /remote:/backup/ /data command will try to use /remote:/backup/ as an identity file for SSH authentication, which is not valid. The cp -r /data /remote/backup/ command will try to copy the /data directory to a local directory named /remote/backup/, not to a remote server. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 18: Automating Tasks; rsync(1) - Linux manual page

The command pam_tally2 -u joe -r will resolve the issue of Joe being unable to log in to the Linux system. The pam_tally2 command is a tool for managing the login counter for the PAM (Pluggable Authentication Modules) system. PAM is a framework for managing authentication and authorization on Linux systems. PAM allows the administrator to define the rules and policies for accessing various system resources and services, such as login, sudo, ssh, or cron. PAM also supports different types of authentication methods, such as passwords, tokens, biometrics, or smart cards. PAM can be used to implement login restrictions, such as limiting the number of failed login attempts, locking the account after a certain number of failures, or enforcing a minimum or maximum time between login attempts. The pam_tally2 command can display, reset, or unlock the login counter for the users or hosts. The -u joe option specifies the user name that the command should apply to. The -r option resets the login counter for the user. The command pam_tally2 -u joe -r will reset the login counter for Joe, which will unlock his account and allow him to log in to the Linux system. This will resolve the issue of Joe being unable to log in to the Linux system. This is the correct command to use to resolve the issue. The other options are incorrect because they either do not unlock the account (usermod -s /bin/bash joe or passwd -u joe) or do not affect the login counter (chage -E 90 joe). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 17: Implementing Basic Security, page 517.