chdev

chdev Command 



Purpose

Changes the characteristics of a device.

Syntax

chdev -l Name [ -a Attribute=Value ... ] [ -f File ] [ -h ]
[ -p ParentName ] [ -P | -T ] [ -q ] [ -w ConnectionLocation
]

Description

The chdev command changes the characteristics of the device specified
with the given device logical name (the -l Name flag).The device can
be in the Defined, Stopped, or Available state. Some changes may not
be allowed when the device is in the Available state. When changing
the device characteristics, you can supply the flags either on the
command line or from a specified File parameter.

When neither the -P nor the -T flags are specified, the chdev command
applies the changes to the device and updates the database to reflect
the changes. If the -P flag is specified, only the database is updated
to reflect the changes, and the device itself is left unchanged. This
is useful in cases where a device cannot be changed because it is
in use; in which case, the changes can be made to the database with
the -P flag, and the changes will be applied to the device when the
system is restarted. The -T flag is used to make a temporary change
in the device without the change being reflected in the database.
It is temporary in that the device will revert to the characteristics
described in the database when the system is restarted. Not all devices
support the -P and -T flags. A device that is in the Defined state
can only have changes applied to the database.

Attention: To protect the Configuration database, the chdev command
is not interruptible. To stop this command before execution is complete
could result in a corrupted database.

You can use the System Management Interface Tool (SMIT) to run this
command for certain devices. To use SMIT, enter:

smit chdev

Flags

-a Attribute=Value	Specifies the device attribute value pairs used
for changing specific attribute values. The Attribute=Value parameter
can use one attribute value pair or multiple attribute value pairs
for one -a flag. If you use an -a flag with multiple attribute value
pairs, the list of pairs must be enclosed in quotes with spaces between
the pairs. For example, entering -a Attribute=Value lists one attribute
value pair per flag, while entering -a 'Attribute1=Value1 Attribute2=Value2'
lists more than one attribute value pair.

-f File	Reads the needed flags from the named File parameter.

-h	Displays the command usage message.

-l Name	Specifies the device logical name, specified by the Name parameter,
in the Customized Devices object class whose characteristics are to
be changed.

-P	Changes the device's characteristics permanently in the Customized
Devices object class without actually changing the device. This is
useful for devices that cannot be made unavailable and cannot be changed
while in the available state. The change can be made to the database
with the -P flag. By restarting the system, the changes will be applied
to the device. This flag cannot be used with the -T flag. Not all
devices support the -P flag.

-p ParentName	Specifies the new device logical name of the parent
device, specified by the ParentName parameter, in the Customized Devices
object class. This flag is used only when changing the parent of the
device. Not all devices support the -p flag.

-q	Suppresses the command output messages from standard output and
standard error.

-T	Changes the characteristics of the device temporarily without changing
the Customized Devices object class for the current start of the system.
This flag cannot be used with the -P flag. Not all devices support
the -T flag.

-w ConnectionLocation	Specifies the new connection location on the
parent. This flag is used only when changing the connection location
of the device. Not all devices support the -w flag.

Security

Access Control: Only the root user and members of the security group
should have execute (x) access to this command.

Auditing Event	Information

DEV_Change	Parameters to the method the cfgmgr command calls.

Examples

1.	To change the retention instructions of a 150M-byte, .25-inch tape
drive to rmt0 (so that the drive does not move the tape to the beginning,
then to the end, and then back to the beginning each time a tape is
inserted or the drive is powered on), enter:

chdev -l rmt0 -a ret=no

The system displays a message similar to the following:

rmt0 changed

2.	To change one or more attributes of the token-ring adapter tok0
to preset values as described in the changattr file, enter:

chdev -l tok0 -f changattr

The system displays a message similar to the following:

tok0 changed

3.	To change the SCSI ID of the available SCSI adapter scsi0 that
cannot be made unavailable or changed due to available disk drives
connected to it, enter:

chdev -l scsi0 -a id=6 -P

The system displays a message similar to the following:

scsi0 changed

To apply the change to the adapter, shutdown and restart the system.

4.	To change the attribute describing which external connector is
to be used by adapter ent0, enter:

chdev -l ent0 -a bnc_select=dix

The system displays a message similar to the following:

ent0 changed

If an error message is displayed because the device is in use, reissue
the chdev command using the -P flag. Shutdown and restart the system
to apply the change to the adapter.

5.	To move a defined tty device tty11 to port 0 on another serial
adapter sa5, enter:

chdev -l tty11 -p sa5 -w 0

The system displays a message similar to the following:

tty11 changed

chdev -l sys0 -a maxuproc=100

Files

/usr/lpp/msg/En_US/cmdcfg.cat	Contains the message catalog file.

/usr/sbin/chdev	Specifies the command file.

Related Information

Commands: lsattr, lsconn, lsdev, lsparent, mkdev, rmdev.

The Devices Overview for System Management in AIX Version 4 System
Management Guide: Operating System and Devices provides information
about adding, changing, moving, and removing devices.

The System Management Interface Tool (SMIT): Overview in AIX Version
4 System Management Guide: Operating System and Devices tells you
about the SMIT application.