Mixed Deck — All LFCS Certification Topics Flashcards

On a Debian-based system, which command shows the installation candidate version of a package before installing it?

Answer: apt-cache policy

`apt-cache policy` displays version priorities and the installation candidate from configured repositories.

Where does systemd-journald store persistent journal data by default?

Answer: /var/log/journal/

/var/log/journal/ holds persistent journal files; if this directory does not exist, logs are stored in /run/log/journal/ and lost on reboot.

What command displays the current default systemd boot target?

Answer: systemctl get-default

systemctl get-default reads the symlink at /etc/systemd/system/default.target and prints its target name.

In DNF/YUM, what is a 'group' and how do you install one?

Answer: A collection of related packages installed together with `dnf group install ''`

DNF groups (like 'Development Tools') bundle related packages for easy bulk installation via `dnf group install`.

Which of the following commands moves and restarts the most recent shell task in the background?

Answer: bg

In a shell environment, if a command is suspended (e.g., by pressing Ctrl+Z), it becomes a stopped job. The `bg` command (background) is used to resume such a suspended job and run it in the background, allowing the user to continue interacting with the shell. The `fg` command would bring a job back to the foreground.

Which iptables target silently discards a packet without sending any response to the sender?

Answer: DROP

DROP silently discards the packet, while REJECT sends an ICMP error message back to the sender.

A system administrator needs to add an existing user, 'testuser', to an existing supplementary group called 'developers'. Which of the following commands will achieve this without removing the user from their current supplementary groups?

Answer: usermod -aG developers testuser

The `usermod -aG` command is used to modify a user's group membership. The `-a` (append) flag is crucial as it adds the user to the specified group(s) without removing them from their existing supplementary groups. The `-G` flag specifies the supplementary group(s).

Which octal value represents 'rwxr-x---' permissions?

Answer: 750

rwx=7, r-x=5, ---=0, so the combined octal is 750.

What is the effect of setting a user's shell to /sbin/nologin in /etc/passwd?

Answer: The user cannot log in interactively

Setting the shell to /sbin/nologin prevents interactive login while still allowing the account to be used for services.

What is the effect of running 'sysctl -w vm.swappiness=10'?

Answer: Changes swappiness only for the current session until reboot

The -w flag writes the value to the live kernel immediately but does not persist across reboots.

An administrator wants to force a user to change their password on next login. Which command accomplishes this?

Answer: chage -d 0 username

chage -d 0 sets the last password change date to the epoch, which forces the system to require a password change at next login.

What happens when you run `apt-get install -f` (or `--fix-broken`)?

Answer: Resolves and fixes broken package dependencies automatically

`apt-get install -f` attempts to correct broken dependencies by installing missing packages or removing conflicting ones.

A file is owned by 'alice' with permissions '640'. User 'bob' is in the same group. What can bob do?

Answer: Read the file only

640 means rw-r-----, giving the group (which includes bob) read-only permission.

Which file in a Debian package contains post-installation scripts?

Answer: postinst

The `postinst` maintainer script runs automatically after a package's files are unpacked.

Which command installs a .deb package and automatically resolves its dependencies from APT repositories?

Answer: apt install ./package.deb

Using `apt install ./package.deb` (with the ./ prefix) installs the local .deb file and fetches missing dependencies from repos.

Which directive in /etc/apt/sources.list specifies that source packages should be available?

Answer: deb-src

Lines beginning with `deb-src` in sources.list tell APT where to find source package archives for `apt-get source`.

What does the `yum history undo ` command do?

Answer: Reverts a specific yum transaction by its ID

`yum history undo ` reverses the changes made by the transaction with the specified ID.

Which file contains the configuration for systemd-journald, including disk usage limits?

Answer: /etc/systemd/journald.conf

/etc/systemd/journald.conf controls journald behavior, including SystemMaxUse, Compress, and Storage settings.

Define Ubuntu

Answer: Debian derived, most popular distribution.

Ubuntu is a popular and widely used Linux distribution that is directly based on Debian, inheriting its robust package management and core system. It is known for its user-friendliness and extensive community support, making it one of the most prevalent Linux distributions globally for both desktop and server use.

What does the command 'setfacl -m u:alice:rx file.sh' do?

Answer: Grants alice read and execute permissions on file.sh via ACL

setfacl -m modifies (adds or updates) an ACL entry; u:alice:rx grants user alice read and execute access.