How to check if the printer is connected to the computer.

1. Unplug the printer from your computer, open a terminal/console window and enter this command. This will display the syslog.

tail -f /var/log/messages

for Ubuntu:

sudo tail -f /var/log/syslog

then reconnect the printer. You should see the system display something like:

Mar 16 11:45:43 localhost kernel: [4298892.030000] hub 2-1.2:1.0: USB hub found
Mar 16 11:45:43 localhost kernel: [4298892.033000] hub 2-1.2:1.0: 4 ports detected
Mar 16 11:45:44 localhost kernel: [4298892.316000] usb 2-1.3: new full speed USB device using uhci_hcd and address 11
Mar 16 11:45:44 localhost kernel: [4298892.409000] hub 2-1.3:1.0: USB hub found
Mar 16 11:45:44 localhost kernel: [4298892.412000] hub 2-1.3:1.0: 4 ports detected
Mar 16 11:45:44 localhost kernel: [4298892.697000] usb 2-1.2.1: new full speed USB device using uhci_hcd and address 12
Mar 16 11:45:44 localhost kernel: [4298892.798000] drivers/usb/class/usblp.c: usblp0: USB Bidirectional printer dev 12 if 1 alt 0 proto 2 vid 0x03F0 pid 0x4311
Mar 16 11:45:44 localhost kernel: [4298892.798000] scsi6 : SCSI emulation for USB Mass Storage devices
Mar 16 11:45:44 localhost kernel: [4298892.975000] usb 2-1.2.2: new full speed USB device using uhci_hcd and address 13
Mar 16 11:45:44 localhost kernel: [4298893.063000] usb 2-1.2.2: not running at top speed; connect to a high speed hub
Mar 16 11:45:45 localhost kernel: [4298893.077000] drivers/usb/class/usblp.c: usblp0: USB Bidirectional printer dev 13 if 0 alt 0 proto 2 vid 0x03F0 pid 0x8804
Mar 16 11:45:45 localhost kernel: [4298893.255000] usb 2-1.3.1: new full speed USB device using uhci_hcd and address 14
Mar 16 11:45:45 localhost kernel: [4298893.342000] usb 2-1.3.1: not running at top speed; connect to a high speed hub
Mar 16 11:45:45 localhost kernel: [4298893.356000] drivers/usb/class/usblp.c: usblp0: USB Bidirectional printer dev 14 if 0 alt 1 proto 2 vid 0x03F0 pid 0x2817
Mar 16 11:45:45 localhost kernel: [4298893.360000] scsi7 : SCSI emulation for USB Mass Storage devices
Mar 16 11:45:45 localhost kernel: [4298893.539000] usb 2-1.3.3: new full speed USB device using uhci_hcd and address 15
Mar 16 11:45:45 localhost kernel: [4298893.624000] usb 2-1.3.3: not running at top speed; connect to a high speed hub
Mar 16 11:45:45 localhost kernel: [4298893.638000] drivers/usb/class/usblp.c: usblp0: USB Bidirectional printer dev 15 if 1 alt 0 proto 2 vid 0x03F0 pid 0x5711
Mar 16 11:45:45 localhost kernel: [4298893.638000] scsi8 : SCSI emulation for USB Mass Storage devices

Then enter this command:

dmesg

You should see something like this displayed:

[4298893.638000] scsi8 : SCSI emulation for USB Mass Storage devices
[4298893.638000] usb-storage: device found at 15
[4298893.638000] usb-storage: waiting for device to settle before scanning
[4298897.802000]   Vendor: HP        Model: Officejet 74xx S  Rev: 1.00
[4298897.802000]   Type:   Direct-Access                      ANSI SCSI revision: 02
[4298897.816000] sd 6:0:0:0: Attached scsi removable disk sdb
[4298897.816000] sd 6:0:0:0: Attached scsi generic sg1 type 0
[4298897.817000] usb-storage: device scan complete
[4298898.366000]   Vendor: HP        Model: LaserJet 2840     Rev: 1.00
[4298898.366000]   Type:   Direct-Access                      ANSI SCSI revision: 02
[4298898.381000] sd 7:0:0:0: Attached scsi removable disk sdc
[4298898.381000] sd 7:0:0:0: Attached scsi generic sg2 type 0
[4298898.384000] usb-storage: device scan complete
[4298898.642000]   Vendor: HP        Model: Photosmart        Rev: 1.00
[4298898.642000]   Type:   Direct-Access                      ANSI SCSI revision: 02
[4298898.657000] sd 8:0:0:0: Attached scsi removable disk sdd
[4298898.657000] sd 8:0:0:0: Attached scsi generic sg3 type 0
[4298898.660000] usb-storage: device scan complete

enter this command:

/usr/lib/cups/backend/hp

You should see something like this displayed:

direct hp:/usb/Photosmart_series?serial=XXXXXXXXXXXXXX "HP Photosmart_series" "hp:/usb/Photosmart_series?serial=XXXXXXXXXXXXXX"
direct hp:/usb/HP_Color_LaserJet_2840?serial=XXXXXXXXXXXX "HP HP_Color_LaserJet_2840" "hp:/usb/HP_Color_LaserJet_2840?serial=XXXXXXXXXXXX"
direct hp:/usb/Deskjet_6980_series?serial=XXXXXXXXXXXXXX "HP Deskjet_6980_series" "hp:/usb/Deskjet_6980_series?serial=XXXXXXXXXXXXXX"
direct hp:/usb/Officejet_7400_series?serial=XXXXXXXXXXXXXX "HP Officejet_7400_series" "hp:/usb/Officejet_7400_series?serial=XXXXXXXXXXXXXX"