It is normally a good idea to mount it as it will allow operations such as reinstalling the boot loader. However, if the file system on ${FILESYSTEM} is corrupt then you may want to avoid mounting it.
D tikti yelhan ad d-yettusali acku aya ad yeǧǧ timahlin am wallus n usebded n usalay n usenker. Acu kan, ma yella anagraw n yifuyla ɣef ${FILESYSTEM} yerreẓ, ahat ad tebɣuḍ ad tḥebseḍ asali-ines.