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System Administration Flashcards

7 cards from real Linux practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 System Administration flashcards as text

  1. Which command would you use to add a user to a supplementary group without changing their primary group?

    Answer: usermod -aG groupname username

    `usermod -aG` appends the user to the specified group while preserving existing group memberships.

  2. What is the effect of setting the SUID bit on an executable file?

    Answer: The file runs with the permissions of the file owner

    SUID (Set User ID) causes the executable to run with the privileges of the file's owner, not the user who runs it.

  3. You need to schedule a one-time task to run at 3:30 PM today. Which command is correct?

    Answer: at 3:30pm

    The `at` command schedules a one-time task at a specified time, unlike `cron` which handles recurring tasks.

  4. Which `/proc` entry shows the currently loaded kernel modules?

    Answer: /proc/modules

    `/proc/modules` lists all currently loaded kernel modules, equivalent to the output of `lsmod`.

  5. What does `journalctl --since '1 hour ago'` do?

    Answer: Shows all journal entries from the last hour until now

    `--since` filters journal output to show entries from the specified time to the present.

  6. A disk partition shows 100% usage but `df -h` reports only 80% used. What is the most likely cause?

    Answer: Reserved blocks for root are consuming space

    ext2/3/4 filesystems reserve 5% of space for the root user by default, which doesn't show in regular `df` output.

  7. Which command shows which package owns a specific file on a Debian-based system?

    Answer: dpkg -S /path/to/file

    `dpkg -S` searches the dpkg database to find which installed package owns a given file path.