modprobe events not logged in /var/log/messages

Question

I'm trying to understand Linux better, specifically driver registration and such so I'm trying to follow what happens when I insert modules and drivers. From what I thought I understood, kernel events such as module insertion and removal are logged in /var/log/messages, but I'm finding inconsistent results depending on the module. For instance, if I load the usb-storage module, the kernel logs the process to /var/log/messages, as demonstrated below:

[root@lily frank]# modprobe -v usb-storage
insmod /lib/modules/2.6.32-573.26.1.el6.i686/kernel/drivers/usb/storage/usb-storage.ko 

[root@lily dev]# cat /var/log/messages | tail
Jun 16 10:03:29 lily kernel: Initializing USB Mass Storage driver...
Jun 16 10:03:29 lily kernel: usbcore: registered new interface driver usb-storage
Jun 16 10:03:29 lily kernel: USB Mass Storage support registered.

But is when I try the same thing with some other modules, the kernel doesn't log the operation, as demonstrated below with the fcoe driver:

[root@lily dev]# modprobe -v fcoe
insmod /lib/modules/2.6.32-573.26.1.el6.i686/kernel/drivers/scsi/scsi_tgt.ko 
insmod /lib/modules/2.6.32-573.26.1.el6.i686/kernel/drivers/scsi/scsi_transport_fc.ko 
insmod /lib/modules/2.6.32-573.26.1.el6.i686/kernel/drivers/scsi/libfc/libfc.ko 
insmod /lib/modules/2.6.32-573.26.1.el6.i686/kernel/drivers/scsi/fcoe/libfcoe.ko 
insmod /lib/modules/2.6.32-573.26.1.el6.i686/kernel/drivers/scsi/fcoe/fcoe.ko 
[root@lily dev]# cat /var/log/messages | tail
Jun 16 10:03:29 lily kernel: Initializing USB Mass Storage driver...
Jun 16 10:03:29 lily kernel: usbcore: registered new interface driver usb-storage
Jun 16 10:03:29 lily kernel: USB Mass Storage support registered.

As you can see the kernel hasn't log anything in /var/log/messages since logging the insertion of the usb-storage module. I find it doesn't log the insertion of a lot of modules.

Can somebody tell me the reason for this behavior? Does it have to do with logging levels or something?

Answer 1

The kernel doesn't log module operations in a centralised manner, each module can log whatever it wants (using printk()). The USB module logs "Initializing USB Mass Storage Driver..." etc.; but the FCoE drivers only log messages when errors occur — if everything loads correctly they're silent. Many modules work this way; the tendency is to minimize the number of messages logged, especially when things are working.