The lab adds three spare disks, image files under /var/lib/le-lab/disks/ that are attached again at every boot, each with an ext4 filesystem and a line in /etc/fstab:

/dev/loop40, meant to be mounted on /mnt/lab;
/dev/loop41, mounted on /mnt/inodes, where an application keeps a cache (/mnt/inodes/cache/, safe to delete) and its data (/mnt/inodes/data/, keep it);
/dev/loop42, mounted on /mnt/scratch, used by the service report-cache.

Write answers to the files in /root/lab-answers/.

Tasks

/mnt/lab isn't mounted, though /etc/fstab has a line for it. Find the error, and fix the line so that mount -a mounts /dev/loop40 there, now and at boot.
The application can't create files in /mnt/inodes/data, yet df -h shows free space. Find out why, write the resource that ran out to /root/lab-answers/2, and make room without touching data/.
/mnt/scratch is nearly full, but du finds almost nothing there. Find the process that holds the space, write its name to /root/lab-answers/3, and free the space.

Hints

findmnt --verify, blkid, lsblk -f; systemctl daemon-reload after editing fstab.
df -h versus df -i.
lsof +L1 (install lsof if it's missing), or ls -l /proc/*/fd looking for (deleted); ps, systemctl status.