Как узнать кто монтирует /dev/shm?

df -HT | grep shm
shm            tmpfs     4.2G   91k  4.2G   1% /dev/shm
shm            tmpfs     6.9G     0  6.9G   0% /var/tmp/portage

grep shm /etc/fstab 
shm                    /var/tmp/portage    tmpfs        size=6512M     0 0

mount | grep shm
shm on /dev/shm type tmpfs (rw,nosuid,nodev,noexec,relatime)
shm on /var/tmp/portage type tmpfs (rw,size=6512M)

shm            tmpfs     4.2G   91k  4.2G   1% /dev/shm