sca_sles15_2025 SCA in SUSE Linux Enterprise Server 15 (2025 Update) Practice Questions

In systemd, targets replace the old SysVinit runlevels. The graphical.target is used to start a graphical user interface with multi-user and networking capabilities, making it the direct equivalent of runlevel 5. The multi-user.target is analogous to runlevel 3 (multi-user, text-mode with networking).

The snapper utility is the recommended tool for managing Btrfs snapshots on SLES. The snapper list command shows existing snapshots with their corresponding numbers. To remove a specific snapshot and free up the space it holds (for changed blocks), the snapper delete command is used.

This statement is false. Access to the at command is controlled by the /etc/at.allow and /etc/at.deny files. If /etc/at.allow exists, only users listed in it may use at. If /etc/at.allow does not exist but /etc/at.deny does, any user not listed in /etc/at.deny may use at. If neither file exists, typically only the root user is allowed. It is not open to all users by default.

The ionice command sets I/O scheduling class and priority. The -c 2 option sets the class to 'Best-Effort', which is the default class. Within this class, the -n 7 option sets the priority to the lowest possible level (0 is highest, 7 is lowest). Applying this to the running process with -p 4567 will make the kernel give this process I/O time only when no other process needs it, effectively solving the resource starvation issue without killing the process. Class 1 is 'Realtime' (highest priority) and Class 3 is 'Idle' (lowest priority, but setting it directly might be too aggressive). Using Best-Effort with the lowest priority is the most balanced approach.

The btrfs subvolume set-default command allows an administrator to define which subvolume is mounted by default when the filesystem is mounted without specifying a subvol or subvolid mount option.

btrfs subvolume snapshot -r creates a read-only snapshot. This is a common operation for creating a point-in-time backup that cannot be accidentally modified.

The correct procedure is to first initialize the new disk as a physical volume using pvcreate. Then, add this new physical volume to the existing volume group with vgextend. Finally, extend the logical volume to use the newly available space in the volume group using lvextend -l +100%FREE. Note that this only extends the logical volume; the filesystem on it must be resized separately (e.g., with resize2fs or xfs_growfs).

The journalctl command uses the -p flag to filter by priority. A single numeric value (e.g., -p 2) will show all messages with that priority level and higher (more severe). The priorities are: emerg (0), alert (1), crit (2), err (3), warning (4), notice (5), info (6), debug (7). Therefore, -p 2 shows critical, alert, and emergency messages. The -b flag restricts the output to the current boot.

The After= directive ensures that this service unit will only be started after the network-online.target and the specified mount unit have been successfully started. This enforces the order of operations.

Requires= specifies a hard dependency. If network-online.target or the mount unit fails to start, this service unit will also fail. remote-fs.target is the standard target that is reached after all remote filesystems (like NFS) listed in /etc/fstab are mounted.

This statement is false. Btrfs snapshots are lightweight and use Copy-on-Write (CoW) technology. When a snapshot is created, it initially consumes almost no additional space. It only starts to consume space as files in the original subvolume are modified or deleted, as the snapshot needs to retain the original data blocks.

A systemd timer unit is the modern and recommended method on SLES 15 for complex scheduling. A single .timer file can be configured with OnBootSec=10min to handle the initial run and OnUnitActiveSec=6h to handle the recurring schedule. This provides more robust control and better logging integration with the systemd journal compared to cron or at.