halt

halt writes file system status information in random access memory (RAM) to the disks and then stops the processor. This command is equivalent to init 0.

halt normally logs the system shutdown to the system log daemon, syslogd, and places a shutdown record in the login accounting file /var/adm/wtmpX.


Hard Disk

The hard disk is made up of magnetic storage devices that read information stored on the disk and write instructions to main memory.

Hard Link

A hard link associates one or more file names with an inode, a data structure describing a file on a disk. Every directory is linked to itself as well as to its parent directory.

Hardware Carrier Detect

When a port is used for both dialing in and dialing out, the modem must be set to use hardware carrier detect so that it raises the data carrier detect (DCD) when there is an active carrier signal on the phone connection. Then when the call hangs up, DCD goes low (the voltage changes) and the modem can be used for dialing out.

Headless System

A headless system is a system without a monitor that is capable of displaying bitmapped graphics (no Frame Buffer ). It cannot display the graphical interfaces required for Web Start installation or programs such as Admintool. When access is needed, a serial ASCII terminal can be connected.

Hidden File

Hidden files are files that have names beginning with a dot (.). An example of a hidden file is .wastebasket.

history

history is a feature of the C shell and Korn shell that allows repetition of previously entered commands. In the Korn shell, the history command is a built-in alias. The history command without arguments displays the last 16 command lines to the screen.

History First Last

In the Korn shell, specifying a range (first last) displays the range of command lines to the screen.

history n

In the Korn shell, specifying history with the n argument (no minus in front of the n) displays all commands from command n onwards.

home Directory

A home directory is the user's own directory, which is set up by the system administrator.

Host

A host is a computer system in a network computing environment.

Host Name

The hostname is a unique name identifying a host machine connected to a network. The name must be unique on the network. The hostname command is used to determine a system's host name.

Host ID

The host ID is a unique system ID which is maintained on the NVRAM . The hostid command is used to determine a system's host ID.

Hot Spare

A hot spare is a slice that automatically comes online and resyncs after a mirror has become unavailable. Hot spares are created in a hot spare pool from which the software can choose an available drive.

Hot Plug

Hotplugging refers to the ability to add or remove hardware components while the system bus and devices are powered up.

HTML

Hypertext Markup Language (HTML) is a page description language for the World Wide Web.