how to determine which filesystems are supported by the running kernel?
 

well, this exactly is the question: how to determine which filesystems are supported by the running kernel?

some claim one can find such info in /proc/filesystems, but i have running samba server on my machine, and the "smbfs" is not present there, although the service runs without visible problems.

2.4.18
red hat 8.0
samba 2.2.5

help will be appreciated.

Do you have a config file of your kernel in /boot ? You could have a look there in the sections 'filesystems'. Maybe /proc/filesystem shows only loaded/present filesystems. And I would guess that smbfs is not in use on a server (more probable on a client).

yep, I have a file named "config" in /boot.
there is a line "CONFIG_SMB_FS=m" in it.
but when will this module be loaded - at startup or at some other time?

The module will be loaded as soon as it is needed. This may be at startup if you have a smb filesystem in /etc/fstab, or later when you mount a network share.