Device Terminology
No of hardware and software devices must interact correctly for the device to function properly.
No of hardware and software devices must interact correctly for the device to function properly.
- Physical devices
- Ports
- Device Drivers
- To put a defined device to available
- Logical devices (/dev)
Note:
Some
of the logical devices are accessed only ODM cannot accessed by
users
Types
of devices
1. Primary
Devices
(RAM,CPU and Motherboard)
2. Secondary
Devices
Hard disk, floppy disk, tape
drive, printers , physical adapters, error special files, null
special files etc.,
a)
Block devices: This
is the structured random
device.
Buffering
is used to provide a block-at-a-time method of access. This is
usually a disk file systems
b)
Character devices: This
is the sequential,
stream oriented
device which does not use buffering
3.
Base
devices :
Keyboard, Mouse
Examples
of block devices
Following
are examples of block devices:
cd0 CD-ROM
fd0,
fd0l, fd0h Diskette
hd1,
lv00 Logical volume
hdisk0 Physical volume
Examples
of character (raw) devices
Following
are examples of character (raw) devices:
console,
lft, tty0 Terminal
lp0 Printer
rmt0 Tape drive
tok0,
ent0 Adapter
kmem,
mem, null Memory
rfd0,
rfd0l, rfd0h Diskette
rhd1,
rlv00 Logical volume
rhdisk0 Physical volume
Note:
Most of the block devices have equivalent character device , For ex,
/dev/hd1 provides buffered access to a logical volume whereas
/dev/rhd1 provides raw access to the same logical volume. (The raw
devices are ususally accessed by the kernel)
Major
and Minor Number
maj,min dev nums
brw------- 1 root system
32,8192 Nov 03 14:19 hdisk3
brw------- 1 root system
32,8194 Nov 03 14:19 hdisk4
brw------- 1 root system
32,8195 Nov 07 07:08 hdisk5
Major no is 32 and minor no is
8192,8194 ...
Major no refers to the s/w
section of code in the kernel which handles that type of device(hard
disk). and minor no to the particular device of that type.
Device
Configuration Database
The
predefined and customized databases store information of all the
logical devices in the system and their attributes. It is managed by
ODM.
Predefined
Database (PdDv) List all the Supported Devices
- Contains all the possible devices supported by the system.s
- Devices in Undefined state
- Output contains column like
Class - what the device does
Type - what model
subclass – Where it is attached
Using
“lsdev
-P”
command can list the devices supported by the system
Customized
Database (CuDv) – List Defined Devices
- List the actual devices used (configured) by the system.
- Displays name,status, Location and description.
- “lsdev -CH” provides information about the Customized devices.
The status column contain 2 states
Available
– Device
ready to use
Defined --
Device is unavailable
Note:
Devices may appear in the Defined state after restart the server,
the reason is either the corresponding device is powered off or
removed from the server.
- Devices with location code are physical devices. Devices without location codes are logical devices. Location codes depend on type of device and the adapter to which the device is connected.
- “lsattr -E -l <resource-name> command provides detailed effective attributes of currently configured devices.
- “lscfg -v” - important Customized database command in which displays complete information about the device in ODM. display vital product data (VPD) such as part no, serial nos, Model architecutre, FRU, part number etc., for all the devices present on the system
Device Status
The most common devices states
are as follows.
1. Undefined
The device is supported device but
not configured. Devices reside in the Predefined Database not
customized database.
2. Defined
The
device is configured but unavailable to use. Devices reside in
Customized databases
are in defined state.
3. Available
The
device is available and ready to use.
Configuring
Devices
1.
“cfgmgr” configure
all self-configuring devices.
2. While configuring the devices,
cfgmgr checks whether the device is support on your AIX system by
checking the PdDv.
3.
Once the information is found in PD DB, it uses complete
information to complete entries into the customized devices database
CuDv.
4.
It also loads the appropriate device driver into the AIX kernel and
makes the logical devices under /dev directory.
5. Finally makes the device to
available state (ODM).
The
above 3 &4 steps are performed by mkdev
command
Changing
Device State
i. To put a defined device to available
#mkdev -l <dev>
ex.,#mkdev -l hdisk1
ii. To put a available device to defined
#rmdev -l <device>
ex.,#rmdev -l hdisk1
iii. To permanently remove from ODM.
#rmdev -dl <device>
ex.,#rmdev -dl hdisk1
Device Addressing
- Location codes are used for device addressing
- Where exactly the device is connected to your m/c.
- Location code is made up of 4 fields of information. Useful in troubleshooting scenarios, referred on LED hardware troubleshooting.
- Devices which are having location code are physical deviecs, not having location code are called logical devices.
- Location codes depend on the type of the device and adapter to which it connects.
- Location code is another way of identifying Physical device.
Format for ex;
AB-CD-EF-GH
for non SCSI/PCI devices
AB-CD-EF-G,H
for SCSI devices
Commands
for displaying Location codes are as follows
#lsdev
-Cc adapter
#lscfg
-vl <name of device>
“lscfg”
list the vital product data including h/w serial no.type, model and
part numbers.
Important Commands
- lsdev --> List all the devices (Predefined and Customized)
- lsattr --> List attributes of the devices
- lscfg --> List the VPD information of the configured (customized) devices
Options for Device Commands
LSDEV
-P
--> Predefined
devices
-C --> Customized devices
-c --> Class type
-H --> Header information
-l --> Specify logical device
name
-p --> child devices of
parent deviecs
-F --> parent device of
particular child device (use “lsparent -Cl hdisk0)
LSATTR
-E
--> Effective
attributes of the devices
-l --> Specify the logical
device name
RMDEV
-l --> logical device name
-d --> completely removes from
ODM.
-SR --> removes all child
devices from the parent device.
LSCFG
#lscfg -vp --> all h/w
information
#lscfg -vl --> for particular
logical device
