Linux in a Nutshell, Fifth Edition

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Chapter 3: Linux Commands

This is the Title of the Book, eMatter Edition

Copyright © 2006 O’Reilly & Associates, Inc. All rights reserved.

-S n

Set the amount of time a disk is inactive before it spins down

and goes into standby mode. Settings from 1 to 240 represent

chunks of five seconds (for timeout values between 5 seconds

and 20 minutes); values from 241 to 251 are increments of 30

minutes (for 30 minutes to 5.5 hours). A value of 252 sets the

timeout to 21 minutes, 253 to the vendor default, and 255 to

20 minutes and 15 seconds.

-T Time cache reads to determine performance.

-t Time device reads to determine performance.

-u [n]

Get or set the interrupt-unmask value for the drive. A value of

1 lets the drive unmask other interrupts and can improve

performance; when used with older kernels and hardware, it

can cause data loss.

-U Unregister an IDE interface. Use this feature and the -R feature

only with hot-swappable hardware, such as very high-end

servers and some laptops. It can damage or hang other

systems, and should be used with caution.

-v Display all appropriate settings for device except -i. This is the

same as the default behavior with no flags.

-w Reset the device. Use as a last resort only; may cause data loss.

-W Enable or disable the write-cache feature for the drive. The

default varies among drive manufacturers.

-x Sets tristate. Use only for hot-swappable devices. See the -R

and -U ...