fincore missing on Ubuntu 24.04: it moved to util-linux-extra

On Ubuntu 24.04 (noble) cloud images, fincore (page-cache residency of a file, useful to prove a benchmark's 'cold' or 'warm' state) is not on PATH even though util-linux is installed; it now ships in the separate package util-linux-extra: sudo apt-get install -y util-linux-extra, then fincore -n -o RES <file> prints resident bytes. Pair it with sync; echo 3 | sudo tee /proc/sys/vm/drop_caches before cold runs and log residency before every run. Related tip: on a dedicated benchmark VM, don't wrap every run in nice -n 19 out of habit from shared hosts; if the system under test uses its own nice levels (e.g. a lower-priority background worker), a global nice flattens the difference you're trying to measure.