LPIC-1 Devices, Filesystems and FHS Practice Test 7 — 15 Questions

Question 1

A system administrator is troubleshooting a server where the /var partition is full, causing services to fail. The administrator deletes old log files in /var/log, but the available space does not increase. Which step should be taken next?

Accepted Answer

Use 'lsof /var/log' to find processes holding deleted file handles, then restart those processes.. When a file is deleted while a process still holds an open file descriptor to it, the file's data blocks are not freed until that process releases the handle. The `lsof /var/log` command identifies such processes, and restarting them forces the kernel to release the deleted inodes, thereby reclaiming the disk space. This is why option C is the correct next step.

Answer

Run 'sync; echo 3 > /proc/sys/vm/drop_caches' to clear cache.

Answer

Remount the /var partition with the 'noatime' option.

Answer

Run 'df -i' to check inode usage.

Question 2

According to the Filesystem Hierarchy Standard (FHS), in which directory should third-party static libraries be installed?

Accepted Answer

/usr/lib. The Filesystem Hierarchy Standard (FHS) specifies that /usr/lib is the correct directory for third-party static libraries that are part of the system's package management. This directory holds libraries that are not dynamically linked and are required by programs in /usr/bin and /usr/sbin, ensuring consistency across the system.

Answer

/lib

Answer

/usr/local/lib

Answer

/opt/lib

Question 3

Which TWO commands can be used to create an ext4 filesystem on a partition?

Accepted Answer

mkfs.ext4 /dev/sdb1. The `mkfs.ext4` command is a direct front-end for creating an ext4 filesystem, making option B correct. Option C is also correct because `mke2fs -t ext4` explicitly calls the ext2/3/4 filesystem creation tool with the ext4 type, producing an identical ext4 filesystem. Both commands ultimately invoke the same underlying `mke2fs` utility with the appropriate filesystem type.

Answer

mkfs.btrfs /dev/sdb1

Answer

mkfs.msdos /dev/sdb1

Answer

mkfs.xfs /dev/sdb1

Question 4

Which THREE directories under the root filesystem are typically used for variable data that changes frequently during system operation, according to FHS?

Accepted Answer

/var. The Filesystem Hierarchy Standard (FHS) designates /var for variable data that changes in size and content during normal system operation, such as logs (/var/log), spool files (/var/spool), and databases (/var/lib). /run holds runtime variable data describing the system since boot, while /tmp is for temporary files that may be deleted on reboot. Together, these three directories are the standard locations for frequently changing data under the root filesystem.

Answer

/usr

Answer

/opt

Question 5

Which TWO utilities can be used to check and repair an XFS filesystem?

Accepted Answer

xfs_repair. C is correct because `xfs_repair` is the primary utility for checking and repairing XFS filesystems, designed to handle metadata corruption and ensure consistency. It is the recommended tool for XFS, similar to how `fsck` works for other filesystems but with XFS-specific optimizations.

Answer

e2fsck

Answer

fsck

Answer

btrfs check

Question 6

You are the system administrator for a small business running a Red Hat Enterprise Linux 8 server that hosts a MySQL database and a web server. The server has two physical disks: a 240GB SSD (sda) with partitions sda1 (boot), sda2 (root), sda3 (swap), and a 1TB HDD (sdb) with a single partition sdb1 mounted at /var/lib/mysql. The server has been running for months without issues. However, this morning you receive alerts that the MySQL database is not accepting new connections. You log in and find that the /var filesystem is 100% full. You check the disk usage and see that /var/lib/mysql uses 90% of the space, but there are also large log files in /var/log/httpd. To free up space immediately and restore database service while planning a permanent solution, you decide to compress old log files and move some database archives to a backup server. After compressing several log files with gzip, the available space increases by only a few MB. You then delete some old database backups from /var/lib/mysql/backup, but the space usage shown by df remains unchanged. What is the most likely cause of this behavior?

Accepted Answer

Some processes have open file handles to the deleted files, preventing the space from being released.. When a file is deleted but still held open by a running process (e.g., the MySQL daemon or httpd), the filesystem does not release the disk space until all file handles are closed. In this scenario, the large log files in /var/log/httpd were compressed with gzip, but the original uncompressed files may still be open by the web server process, so deleting them (or the old database backups) does not free space until the process is restarted or the handles are released. This explains why df still shows 100% usage despite the deletions.

Answer

The disk quota for the mysql user is exceeded, so deletions do not reduce usage.

Answer

The SSD is not TRIM-enabled, so deleted blocks are not reclaimed.

Answer

The filesystem was remounted read-only due to errors, so deletions are not permanent.

Question 7

You are a Linux administrator for a large e-commerce company. The company's application server runs Ubuntu 22.04 and uses a Btrfs filesystem for the /srv/app partition to take advantage of snapshots and compression. During a routine maintenance window, you create a snapshot of the /srv/app subvolume using 'btrfs subvolume snapshot /srv/app /srv/app_snapshot'. Later, you need to roll back to the snapshot because of a failed application update. You attempt to delete the original subvolume with 'btrfs subvolume delete /srv/app', but the command fails with the error: 'ERROR: cannot delete '/srv/app': Device or resource busy'. You check that no processes are using the directory with lsof, and it shows no open files. The /srv/app subvolume is the default subvolume and is mounted via fstab with the option 'subvol=/' (the root of the Btrfs filesystem). What is the most likely reason for the deletion failure, and how should you proceed?

Accepted Answer

The subvolume is the default subvolume (ID 5) and cannot be deleted while it is the mounted root; use 'btrfs subvolume set-default <new_subvol_id> /srv/app', then unmount and remount with the new default subvolume, then delete the old subvolume.. The error occurs because the subvolume at /srv/app is the default subvolume (ID 5) of the Btrfs filesystem, and it is currently mounted as the root of the filesystem via the 'subvol=/' mount option. A default subvolume cannot be deleted while it is mounted because the kernel treats it as the top-level volume. To delete it, you must first set a different subvolume as the default using 'btrfs subvolume set-default', then unmount and remount the filesystem with the new default, after which the original subvolume can be safely deleted.

Answer

The subvolume is read-only; change it to read-write with 'btrfs property set -f /srv/app ro false'.

Answer

You cannot delete the subvolume because it is the default subvolume; you must first delete the snapshot and then recreate the original.

Answer

The Btrfs kernel module has a readahead lock on the subvolume; wait for it to expire or reboot.

Question 8

You are a junior system administrator tasked with adding a new 500GB HDD to a Debian 11 server that will be used for backup storage. The server currently has a 120GB SSD with two partitions: sda1 (boot) and sda2 (root). You have physically installed the HDD and it is recognized as /dev/sdb. You need to partition the disk with a single partition covering the entire disk, format it as ext4, and ensure it is automatically mounted at /backup at boot time. Which sequence of commands should you execute to accomplish this?

Accepted Answer

sudo parted /dev/sdb mklabel gpt && sudo parted /dev/sdb mkpart primary ext4 0% 100% && sudo mkfs.ext4 /dev/sdb1 && echo '/dev/sdb1 /backup ext4 defaults 0 2' | sudo tee -a /etc/fstab && sudo mount -a. Option A is correct because it first creates a GPT partition table on /dev/sdb with parted, then creates a single primary partition spanning the entire disk, formats that partition (not the raw disk) as ext4, adds an fstab entry for automatic mounting at /backup, and finally mounts all filesystems. This sequence ensures the disk is properly partitioned, formatted, and configured for persistent boot-time mounting.

Answer

sudo mkfs.ext4 /dev/sdb1 && echo '/dev/sdb1 /backup ext4 defaults 0 2' | sudo tee -a /etc/fstab && sudo mount -a

Answer

sudo mkfs.ext4 /dev/sdb && echo '/dev/sdb /backup ext4 defaults 0 2' | sudo tee -a /etc/fstab && sudo mount -a

Answer

sudo fdisk /dev/sdb (create partition) && sudo mkswap /dev/sdb1 && echo '/dev/sdb1 /backup ext4 defaults 0 2' | sudo tee -a /etc/fstab && sudo mount -a

Question 9

You manage a CentOS 7 server that runs a critical application storing data on an XFS filesystem mounted at /data. The server experiences an unexpected power outage. After rebooting, the application fails to start, and you suspect filesystem corruption. You boot into single-user mode and attempt to mount /data, but the mount fails with an error: 'mount: /dev/sdb1: can't read superblock'. You run 'xfs_repair -n /dev/sdb1' and it reports the log is dirty and must be replayed or the filesystem repaired with the -L option (force log zeroing). You want to recover the filesystem with minimal data loss. Which action should you take?

Accepted Answer

Run 'xfs_repair -L /dev/sdb1' to force log replay and repair.. The correct answer is A because xfs_repair -L /dev/sdb1 forces the log to be zeroed (cleared) and then performs a full filesystem check and repair. This is necessary when the log is dirty and cannot be replayed normally due to corruption, such as after an unclean shutdown. The -L option is the standard recovery method for XFS when the log is damaged, and it minimizes data loss by only discarding the log (which contains metadata changes that were not yet written to disk) while preserving the rest of the filesystem data.

Answer

Mount the filesystem with the 'norecovery' option to bypass the log and then attempt to repair.

Answer

Run 'fsck -y /dev/sdb1' to automatically repair.

Answer

Run 'xfs_admin -U generate /dev/sdb1' to generate a new UUID and then mount.

Question 10

You are a system administrator at a hosting company. A customer reports that their website hosted on a shared LAMP server is returning error 500. The server runs Ubuntu 22.04 with Apache, MySQL, and PHP. You log in and find that the /var partition (on /dev/sda3, ext4) is almost full. You identify that the MySQL database directory /var/lib/mysql contains several large binary logs that are no longer needed. You delete the binary logs using 'rm -f /var/lib/mysql/mysql-bin.*'. However, the available space does not increase. You also notice that an inode leak is suspected. You check inode usage with 'df -i' and see that the partition has plenty of free inodes. You then check with 'lsof | grep deleted' and see several entries for mysqld holding deleted files. What is the correct procedure to free the space?

Accepted Answer

Restart the MySQL service with 'systemctl restart mysql'.. When a file is deleted while a process (like mysqld) still holds an open file descriptor to it, the file's inode remains allocated and the disk space is not freed until the process releases the descriptor. Restarting the MySQL service (systemctl restart mysql) causes mysqld to close all open file descriptors, allowing the kernel to release the deleted binary logs' inodes and reclaim the disk space.

Answer

Use 'dpkg --purge mysql-server' to completely remove MySQL, then reinstall it.

Answer

Run 'e2fsck -f /dev/sda3' to reclaim inodes and fix filesystem inconsistencies.

Answer

Move the binary logs to a different partition using 'mv /var/lib/mysql/mysql-bin.* /tmp/' and then delete them.

Question 11

A user reports that a USB drive (device /dev/sdc1) is not automatically mounted at boot. The output of 'blkid' and the relevant line in /etc/fstab are shown in the exhibit. What is the most likely cause of the failure?

Accepted Answer

The UUID in /etc/fstab does not match the device's UUID.. The UUID in /etc/fstab does not match the UUID reported by blkid, causing the system to not find the device at boot. Option A is incorrect because the filesystem is detected by blkid. Option B is incorrect because the mount point exists (otherwise manual mount would fail). Option D is incorrect because the filesystem type matches. Option E is incorrect because the device file exists.

Answer

The device /dev/sdc1 does not exist.

Answer

The mount point /media/usb does not exist.

Answer

The filesystem is corrupted and requires fsck.

Answer

The filesystem type is incorrectly specified as vfat.

Question 12

According to the Filesystem Hierarchy Standard (FHS), which TWO directories are intended for variable data that persists across system reboots? (Choose two.)

Accepted Answer

/run. /var is the primary directory for variable data such as logs, databases, and spools. /run is used for runtime variable data that must persist only during a session, but FHS specifies it for variable data as well. /opt is for add-on software, /tmp is for temporary files (may be cleared on reboot), and /usr/local is for locally installed software, not variable data.

Answer

/opt

Answer

/usr/local

Answer

/tmp

Question 13

An administrator is configuring a new server with two SATA disks. The first disk (/dev/sda) holds the root filesystem. The second disk (/dev/sdb) is intended to provide additional storage for user home directories. The administrator partitions /dev/sdb using 'fdisk' to create a single partition /dev/sdb1, formats it with 'mkfs.ext4' and adds the following line to /etc/fstab: '/dev/sdb1 /home ext4 defaults 0 2'. After rebooting, the /home directory is empty and the command 'df -h' does not show /dev/sdb1. However, running 'mount /dev/sdb1 /home' manually works perfectly. The disk is not listed in 'cat /proc/mounts' before the manual mount. What is the most likely cause of this issue?

Accepted Answer

The filesystem on /dev/sdb1 has errors and needs to be checked with fsck before mounting.. The fstab entry uses the device file /dev/sdb1 rather than a UUID or filesystem label. While this can work, it is fragile if device ordering changes. However, the most common cause of a device not mounting at boot when the device file is correct is that the filesystem has errors requiring fsck. Option B is incorrect because the device file is correct (manual mount works). Option C is incorrect because an empty /home directory does not prevent mounting. Option D is incorrect because _netdev is for network filesystems. Option A is correct because if the filesystem has errors, the system may skip the mount at boot to avoid data loss, but manual mount with 'mount' bypasses fsck checks.

Answer

The fstab entry is missing the _netdev option, which is required for local SATA disks.

Answer

The /home directory is not empty and contains files that conflict with the mount.

Answer

The fstab entry uses the device file /dev/sdb1 instead of the UUID.

Question 14

Refer to the exhibit. A user tries to execute a script on a mounted filesystem but gets a permission denied error. The script has execute permissions. What is the most likely cause?

Accepted Answer

The filesystem is mounted with the 'noexec' option.. The mount options include 'noexec', which prevents execution of binaries or scripts on that filesystem regardless of file permissions.

Answer

The script is not executable for the user.

Answer

The user does not have read permission on the script.

Answer

The filesystem is full.

Question 15

Refer to the exhibit. The 'mount -a' command fails for the NFS mount. What is the most likely cause?

Accepted Answer

The NFS server is not exporting the directory or is unreachable.. The NFS server (192.168.1.100) is not reachable or the export is not available, causing the superblock read failure. The '_netdev' option indicates network filesystem, but it still fails if the network is not ready or server is down.

Answer

The local mount point /mnt/nfs does not exist.

Answer

The filesystem type 'nfs' is not supported by the kernel.

Answer

The 'defaults' option is missing for the NFS entry.