Essential Commands

An administrator needs to combine two sorted text files, /tmp/a.txt and /tmp/b.txt, into a single sorted stream on standard output while also removing duplicate lines that appear in both files. Which command should be used?

A user wants to find all files in /var/log that have been modified within the last 2 days. Which command should they use?

Which THREE of the following statements about Linux file permissions are correct?

A DevOps engineer wants to list all running processes sorted by memory usage in descending order. Which command should be used?

Which THREE of the following commands can be used to view the contents of a compressed file named 'file.gz' without permanently decompressing it? (Choose exactly three.)

Which TWO commands can display the current environment variables?

Refer to the exhibit. The output of 'ps aux' shows a process named 'process_hog' with PID 1234 consuming 99.5% CPU. The process is stuck in an infinite loop and does not respond to SIGTERM. Which signal should be used to forcefully terminate it?

You are managing a Linux server that hosts a critical web application. The server is running low on disk space in the root filesystem, and you need to free up space urgently. You run 'df -h' and see that /dev/sda1 is mounted on / and is 95% full. You also notice that /var/log/messages is over 2 GB in size. The application writes logs to /var/log/app.log, which is also large. The server has a separate /var partition that has plenty of free space. The application must continue running with minimal downtime. You need to compress and rotate logs without losing any data, and ensure that the root filesystem has at least 10% free space. Which of the following actions should you take first to achieve this goal?

A system administrator needs to change the ownership of the file /var/www/html/index.html from user alice to user bob, and also change the group to webdev. Which command should they use?

A cron job runs a script every hour but sometimes fails because the script cannot find commands like 'tar' and 'gzip'. The script works when run manually from a terminal. What is the best fix?

An administrator is diagnosing disk space and wants to see the total size of the /var/log directory and all its contents in human-readable units, without listing every individual file. Which command provides exactly this summary?

A system administrator wants to kill a process with PID 1234 that is not responding to SIGTERM. Which command will forcefully terminate it?

A user wants to continuously monitor a log file that is being written to by a running service. Which command achieves this?

Based on the exhibit, which process will be affected if the root user runs 'kill 5678'?

A user 'dba' tries to login via SSH and fails. Based on the exhibit, what is the most likely cause?

A DevOps engineer wants to measure how long a specific command takes to execute. Which command should be used?

A junior administrator is troubleshooting a server and needs to inspect the manual page for the 'ip' command, but the system is a minimal install where the man pages for that package were not installed. The administrator still wants the short one-line usage summary for 'ip' printed directly to the terminal. Which command should they run?

Refer to the exhibit. The administrator receives alerts that the root filesystem is almost full. Which command could free up space by removing old log files?

A system administrator needs to create a hard link named /home/user/report_hardlink to an existing file /data/reports/report.txt. Which command should be used?

Match each Linux permission type to its symbolic representation.

A user wants to set the permissions of a file to 'rwxr-xr--'. Which octal permission value should they use with chmod?

An administrator needs to change the ownership of the directory /srv/www to user webadmin and group webteam, including all existing files and subdirectories. Which command accomplishes this?

A process is consuming 99% CPU and is unresponsive to normal shutdown requests. After running 'top', you see the PID is 1234. What is the most appropriate command to stop the process gracefully first?

A user needs to locate all regular files under /etc that are larger than 1 MB and have not been accessed in the last 30 days. Which command finds these files?

To display the first 10 lines of a file named 'log.txt', which command is correct?

A system administrator wants to display a list of all currently running processes with their parent process IDs. Which command is most appropriate?

A system administrator notices that the disk space on the root filesystem is at 95% usage. After investigating, they find that a large log file named 'access.log' in /var/log is taking up significant space. The administrator deletes the file using 'rm /var/log/access.log' but the disk usage remains at 95%. Running 'df -h' still shows the same usage. What is the most likely cause and the correct next step?

A system administrator needs to identify the absolute path of the executable that would be run when typing the command 'ls'. Which command should they use?

A user wants to view the contents of a compressed log file /var/log/syslog.2.gz without decompressing it first. Which command should they use?

An administrator must change the ownership of /srv/project and every file and directory beneath it to user alice and group devs, without altering permissions. Which command should be used?

A user reports that they cannot delete a file named 'important.txt' located in their home directory. The file is owned by the user and the user has write permission on the directory. Running 'rm important.txt' produces the error: 'rm: cannot remove 'important.txt': Operation not permitted'. The user has also tried using 'sudo rm' but gets the same error. Which of the following is the most likely cause and correct solution?

A user reports that a shell script 'backup.sh' in /home/user/scripts fails to execute. What is the most likely cause?

An administrator needs to change the group ownership of the directory /srv/project and all of its existing contents to the group developers, without altering the user ownership. Which command should be used?

Which TWO commands can be used to display the current working directory?

A technician must create a hard link named 'report_link' to an existing file '/data/report.txt'. Which command should be used?

A system administrator has a cron job that runs a backup script. The script requires the variable BACKUP_DIR to be set, but the administrator cannot modify the script. Which is the most appropriate place to define the variable for cron?

You are a system administrator for a company that runs a web server on a Linux system. The web server logs are stored in /var/log/nginx/access.log. The log file grows rapidly and rotates weekly via logrotate. The system has been running for several months. Recently, the development team reported that the web server is responding slowly. You suspect that the disk I/O might be high due to log file activity. You check the disk usage and find that /var/log/nginx/access.log is 4 GB, and the rotated logs (access.log.1.gz, access.log.2.gz, etc.) total another 10 GB. The /var partition has 20 GB total, so it's 70% full. You decide to reduce the disk usage by compressing the current log file and truncating it without stopping the nginx service. Which command sequence should you use to safely achieve this?

A backup script must create a compressed archive of the /etc directory, preserving file permissions and timestamps. Which command should be used?

Which command displays the amount of free and used memory in the system?

A junior administrator needs to create a new empty file named report.txt in the current working directory. They want to ensure that if the file already exists, its contents are not altered. Which command should they run?

An administrator runs `ls -l` and sees a file entry whose permission string begins with a lowercase `l`. What does this indicate about the entry?

A junior admin runs 'ls -l' and sees permissions '-rwxrwxr-x' on a file. What is the octal representation?

Which TWO commands can be used to display the contents of a text file that has been compressed with gzip without decompressing it to disk?

A support engineer must copy the directory /srv/appdata, including every subdirectory, hidden file, and preserved permission bits and timestamps, to /backup/appdata on the same host. Which command accomplishes this?

Which TWO commands can be used to display the contents of a text file page by page? (Select two.)

A systems administrator needs to add a new user 'jdoe' with a home directory in /export/home, a UID of 1500, and an expiry date of 2025-12-31. Which command should they use?

A storage administrator needs to identify which filesystem is mounted at /mnt/data and display the mount options currently in effect for it, using a single command that reads the kernel mount table. Which command should be used?

A user is unable to write to a file. The output of 'ls -l file' shows '-r--r--r--'. Which command will grant write permission to the owner?

A developer reports that a compiled binary 'app' fails to execute with 'Permission denied' error when run from a mounted directory '/mnt/software'. The binary has execute permissions for all users. What is the most likely cause?

A user wants to find the location of the 'grep' binary. Which command should they use?

A user needs to view the contents of a compressed log file /var/log/syslog.gz without first decompressing it. Which command should they use?

To compress a file while preserving the original file, which command should be used?

Refer to the exhibit. The /var partition is 100% full. Which command can be used to find the largest files in /var/log to free up space?

A system administrator configures a new server with multiple disks. After partitioning and formatting, they mount a partition to /data. Several days later, they notice that the /data filesystem is full, but 'du -sh /data' reports only 2 GB used, while the partition is 100 GB. 'df -h' shows /data is 98% full. What is the most likely cause and the correct action?

A system administrator needs to list all files in the current directory, including hidden files, in a long listing format sorted by modification time (oldest first). Which command achieves this?

A user needs to view the contents of a large text file one screen at a time. Which command is best for this?

Which THREE commands can change the priority of an already running process?

What is the purpose of the chmod 755 command in this exhibit?

A system administrator needs to change the group ownership of a file to 'developers' and set the setgid bit on a directory. Which two commands accomplish these tasks? (Choose two.)

Which TWO commands can be used to display the current working directory? (Choose exactly two.)

A security audit reveals that a sensitive file '/etc/shadow' has been modified. The file's permissions are set to 600 and owned by root. However, the audit logs show that a service account 'webapp' was able to read the file. The 'webapp' user is not in the root group. Which of the following is the most likely method the 'webapp' user used to read the file?

A security analyst needs to search for the literal string 'error: failed to connect' in all .log files under /var/log, including subdirectories. The search should be case-insensitive and display line numbers. Which command should they use?

A junior administrator needs to create a symbolic link named /usr/local/bin/editor that points to /opt/tools/vim.bin. The link must be created without overwriting any existing file at the destination. Which command accomplishes this?

A developer wants to change the ownership of a directory and all its contents recursively to user 'appuser' and group 'appgroup'. Which command accomplishes this?

A user wants to view the contents of a compressed file file.txt.gz without decompressing it permanently. Which two commands can be used? (Choose two.)

A user needs to see the contents of a gzip-compressed file 'data.txt.gz' without decompressing it. Which command is appropriate?

A system administrator needs to identify which processes are consuming the most CPU and memory on a Linux server. Which TWO commands can provide a real-time, interactive view of process resource usage? (Choose two.)

An administrator needs to replace all occurrences of the string 'foo' with 'bar' in all files under /etc/config, but only in files ending with .conf. The replacement must be done in-place, and backup copies should be created with a .bak extension. Which command accomplishes this?

To check the disk usage of the /var/log directory in a human-readable format, which command is appropriate?

An administrator runs 'ls -la' and sees the following entry for a file: 'lrwxrwxrwx 1 root root 24 Jan 10 12:00 link -> /etc/passwd'. If the target file /etc/passwd is deleted, what happens to the link file?

An administrator wants to print the last field of each line from a CSV file 'data.csv' (comma-separated). Which awk command accomplishes this?

A technician must locate every regular file beneath /var that is larger than 100 MB and was modified more than 30 days ago, then list them. Which TWO find expressions achieve this? (Choose two.)

Which TWO commands can be used to view the last 10 lines of a file and also follow new lines as they are written?

Which THREE of the following commands can be used to search for a string in multiple files and display the matching lines?

A junior administrator needs to create a compressed archive of the /etc directory that preserves file ownership and permissions, and writes it to /backup/etc.tar.gz. Which single command accomplishes this?

A user reports that they cannot run a script because it says 'Permission denied'. The script is owned by root and has permissions -rw-r--r--. Which command would allow the user to execute the script?

A DevOps engineer is writing a continuous integration pipeline that runs a script to deploy an application. The script is stored in a Git repository and is executed on a build server. The script works locally on the engineer's workstation, but when executed on the build server, it fails with '/bin/sh: line 12: somecommand: command not found'. The 'somecommand' is a standard Linux tool that is installed on the build server. The build server uses a minimal Docker container. Which of the following is the most likely cause and solution?

A server's root filesystem is filling up. An administrator needs to find the largest regular files under /var, sorted from largest to smallest, while avoiding errors from unreadable directories that are not owned by the administrator. Which command is most appropriate?

Which THREE commands can be used to view the contents of a file?

A system administrator needs to find all files in /var/log that have been modified in the last 7 days. Which command accomplishes this?

A system administrator notices that '/var/log/syslog' has grown very large and is consuming significant disk space. The administrator wants to identify the largest log files in the '/var/log' directory hierarchy. Which command should the administrator use?

A support engineer must copy the file /etc/hosts to /tmp/hosts.backup but only if /tmp/hosts.backup does not already exist, so that an existing backup is never overwritten. Which command performs this conditionally?

An administrator needs to inspect the first few lines of a very large log file /var/log/syslog without loading the entire file into memory, and also needs to follow new entries as they are appended in real time. Which TWO commands or command combinations satisfy these requirements? (Choose two.)

An administrator needs to compress a directory named 'project' into a tarball with maximum compression using gzip. Which command is appropriate?

A junior administrator needs to display the first 10 lines of a file named 'data.csv'. Which command should they use?

A user reports that a script fails with 'Permission denied' when executed. The script has permissions -rw-r--r-- and is owned by the user. Which command should the user run to make the script executable for the owner only?