sca_sles15_2025 Sample Questions & Answers

The btrfs balance command is used to rebalance data across devices in a Btrfs filesystem. Running btrfs balance start /data without any filters will re-stripe all data and metadata chunks across the available devices, leading to a more even distribution. This is particularly useful after adding or removing devices.

The find command uses the -perm option to search for files with specific permissions. The SUID bit corresponds to the octal value 4000. Using a forward slash (/4000) tells find to match files where any of the specified permission bits are set. This is the correct way to find all files with the SUID bit, regardless of their other permissions.

Btrfs natively integrates volume management and filesystem capabilities. Creating a Btrfs filesystem with RAID1 profile (mkfs.btrfs -d raid1 -m raid1 /dev/sdb /dev/sdc) directly meets the mirroring requirement. Furthermore, Btrfs provides built-in, highly efficient Copy-on-Write snapshots, which perfectly satisfies the need for instantaneous, space-efficient backups. This single technology elegantly solves both requirements.

When adding a new repository with zypper addrepo, it is often added in a disabled state by default as a safety measure. The administrator must explicitly enable it using the command zypper modifyrepo --enable new_repo (or -e). Until it is enabled, zypper will not use it to search for or install packages.

The renice command is used to alter the scheduling priority of a running process. A higher nice value (from -20 to 19) means a lower priority. To decrease the priority of the process, you must provide a positive nice value. The command renice 10 25123 sets the nice value of PID 25123 to 10, making it yield CPU time more readily to other processes. A regular user can only increase the nice value (decrease priority), while root can also decrease the nice value (increase priority).

The lvcreate command is used to create LVM snapshots. The correct syntax uses -L or --size to specify the size of the snapshot volume (which stores the changes), -n or --name to give the snapshot a name, and -s or --snapshot followed by the path to the original logical volume.

This solution meets all requirements. A RAID5 logical volume created across all four 2TB disks provides a total usable capacity of (4-1) * 2TB = 6TB and can tolerate the failure of one disk. A striped (RAID0) logical volume provides the best performance by writing data across multiple disks simultaneously, which is ideal for a temporary scratch space where redundancy is not required.

The wicked ifreload command is designed to reread the configuration files for network interfaces and apply any changes. Specifying the interface name (eth0) or using the --all flag will trigger wicked to reconfigure the interface according to the updated ifcfg-eth0 file. This is the correct method to apply persistent network changes without a full reboot or service restart.

The sticky bit (octal 1000, shown as 't' in ls -l output) is primarily used on world-writable directories like /tmp. When set, it restricts file deletion. A user can create files, but can only delete or rename the files that they themselves own, regardless of the directory's write permissions. This prevents users from interfering with each other's files in a shared space.

The zypper patch command is used to install official patches from SUSE. To filter these patches by a specific type, the --category flag is used. Specifying --category security instructs zypper to install only those patches that have been classified as 'security' updates, ignoring other categories like 'recommended' or 'optional'.