Lsmod

lsmod is a command on Linux systems that lists each loadable kernel module that is loaded.
Example output from lsmod:
Module Size Used by
af_packet 27392 2
8139too 30592 0
snd_cs46xx 96872 3
snd_pcm_oss 55808 1
snd_mixer_oss 21760 2 snd_pcm_oss
ip6table_filter 7424 1
ip6_tables 19728 1 ip6table_filter
ipv6 290404 22
xfs 568384 4
sis900 18052 5
libata 169920 1 pata_sis
scsi_mod 158316 3 usb_storage,sd_mod,libata
usbcore 155312 6 ohci_hcd, usb_storage, usbhid
The Module column contains the name of a module. The Size column indicates the size in bytes of a module. The Used by column indicates how many times the module is in use by running programs. To the right of that is a list of other modules which refer to this one, but this list is sometimes incomplete. If the module controls its own unloading via a can_unload routine then the used-by count shows as -1, irrespective of the actual count.