The "nameserver" directive in the /etc/resolv.conf file allows you to specify a DNS server, making "nameserver 8.8.8.8" the correct answer. The "search" directive is used to create a list for host-name lookups. The other options are invalid.

The "-l" option to the "ls" command displays a long listing format which includes what user owns the given file. Running "ls" without any options simply displays the file. The "-a" option is used to display all files, even hidden files that start with a period. The "-U" option prevents the "ls" command from sorting and instead lists entries in directory order.

The correct command is "chmod 700 runme.sh". It assigns rwx permissions to the owner of the file and no permissions to the group of the file and others. The "chmod 777 runme.sh" command assigns rwx permissions to every user on the system. The "chmod runme.sh +xuser" uses invalid syntax. The "chown" command is used to change file and/or group ownership of a file or directory without changing the underlying permissions.

An attack surface is an area of a system that is potentially vulnerable to hacking. One way to decrease the attack surface is to remove any unused packages or services that exist on a system.

The "pvcreate" command initializes Physical Volumes (PVs) for use by LVM. The "vgextend" command adds one or more PVs to a VG and thus increases the space available for LVs in the VG. The format of the "vgextend" command is "vgextend VG_NAME PV...", making "pvcreate /dev/sdj && vgextend vg_db_data /dev/sdj" the correct answer. NOTE: "&&" is a logical AND operating, meaning that the command that follows it will only execute if the preceding command succeeds.

The exit status of a shell script is the exit status of the last command executed in the shell script, making "uptime" the correct answer. To override this behavior, use the exit command followed by the desired exit status. All scripts and commands have an exit status. Exit statuses fall between 0 and 255.

The "lvs" command displays information about Logical Volumes, making it the correct answer. The "pvs" command displays information about Physical Volumes. The "vgs" command displays information about Volume Groups. The "logical-volumes" command is invalid.

Of the given commands, "du" is the best answer as it can display the disk usage for a directory and all of its contents recursively.

The "lvcreate" command creates a Logical Volume (LV). The "pvcreate" command initializes Physical Volumes (PVs) for use by LVM. "vgcreate" creats Volume Groups (VGs). "logvol" is not a valid command.

The "systemctl get-default" command displays the default target that they system is configured to boot into. The "systemctl status" command displays service status information, but does not display the default target. The other commands are invalid.