Devices

Devices:

1. Physical Devices: Actual hardware that is connected in some way to the system
2. Ports: The physical connectors / adaptors in the system where physical devices attached.  Most ports are programmable by system software to allow attachment of many different types of devices.
3. Device Drivers: Software in the kernel that controls the activity on a port and format of the data that is sent to device.
4. Logical Devices: Software interfaces (special files) that present a means of accessing a physical device to the user and application programs.

       Data appended to logical devices will be sent to appropriate device driver.

       Data read from logical devices will e read from appropriate device driver.

5. /dev:  The directory which contains all the logical devices that can be directly access by the user.

Listing of /dev directory

# ls –l /dev

brw-rw-rw   root system tdo

crw-rw-rw   root system td1

Block Device: Block device is random access device, buffering is used to provide a block at a time of access. Usually disks file systems only.

Character Device: Character device is sequential stream oriented device which provide no buffering.

Types of devices:

i)                    Predefined devices (All system supported devices)

ii)                  Defined devices (All configured devices)

Listing all devices

# lsdev  

Listing all supported devices (predefined)

# lsdev –P –H ( -P pulls data from predefined database, -H pulls data for header)

class   type   subclass     description

tape    4mm     scsi          4.0 GB mm tape

# lsdev –Pc tape (c stands for class)

Using with smit listing all supported devices (predefined)

# smit devices > list devices > list all supported devices

Listing all configured devices (customized)

# lsdev – C – H ( -C pulls data from customized database, -H pulls data for header)

Using with smit listing all configured devices (customized)

# smit devices > list devices > list all defined devices

Device configuration:
# mkdev -l or cfgmgr 
Remove the device:
# rmdev -l or rmdev -dl 
To list the attributes of the device
# lsattr -El tape
To list all the devices currently connected to the system
# lscfg  

To see the disk size

            # bootinfo –s hdisk0
           

Device states: