Chapter 9 Study Cards

Question 1

chage

Answer 1

The chage command enables you to modify account settings relating to account expiration.

Question 2

Coordinated Universal Time (UTC)

Answer 2

A time closely related to Greenwich Mean Time (GMT).

Question 3

cron

Answer 3

The cron program is a daemon, so it runs continuously, looking for events that cause it to spring into action.

Question 4

Cron job

Answer 4

A program or script that’s run at a regular interval by the cron daemon. See also system cron job and user cron job.

Question 5

daemon

Answer 5

A daemon is a program that runs continuously in the background waiting for an event to trigger it to perform some action.

Question 6

File server

Answer 6

A computer or program that delivers files to other computers via network protocols upon request. Examples of file-server programs include NFS, Samba, and FTP.

Question 7

GMT

Answer 7

The time in Greenwich, England, unadjusted for daylight saving time. Linux systems use this time internally and adjust to local time by knowing the system’s time zone. See also Coordinated Universal Time (UTC).

Question 8

Greenwich Mean Time (GMT)

Answer 8

The time in Greenwich, England, unadjusted for daylight saving time. Linux systems use this time internally and adjust to local time by knowing the system’s time zone. See also Coordinated Universal Time (UTC).

Question 9

Group administrator

Answer 9

A person with administrative authority over a group. A group administrator can add or delete members from a group and perform similar administrative tasks.

Question 10

groups

Answer 10

Linux uses groups as a means of organizing users. In many ways, groups parallel users. In particular, they’re defined in similar configuration files, have names similar to usernames, and are represented internally by numbers (as are accounts).

Question 11

Hardware clock

Answer 11

A clock that’s built into a computer’s hardware. The hardware clock maintains the time when the computer is powered down. See also software clock.

Question 12

Log file

Answer 12

A text file, maintained by the system as a whole or by an individual server, in which important system events are recorded. Log files typically include information about user logins, server access attempts, and automatic routine maintenance.

Question 13

Log rotation

Answer 13

A routine maintenance process in which the computer suspends recording data in log files, renames them, and opens new log files. This process keeps log files available for a time, but ultimately it deletes them, preventing them from growing to consume all available disk space. Also called log rotation.

Question 14

Network Time Protocol (NTP)

Answer 14

A network protocol and server enabling one computer to set its clock based on the value maintained by another clock.

Question 15

Skeleton directory

Answer 15

A directory, typically /etc/skel, that holds files that should be copied to each new user’s home directory as the user’s account is created.

Question 16

Software clock

Answer 16

A type of clock maintained by a running Linux system and used by most software programs that must refer to the time. See hardware clock.

Question 17

Stratum

Answer 17

In the context of the Network Time Protocol (NTP), the distance of a server from an atomic clock or other original time source. Stratum 0 servers are such sources but can’t be contacted directly except by a stratum 1 server. Stratum 2 servers set their clocks from stratum 1 servers, stratum 3 servers set their clocks from stratum 2 servers, and so on.

Question 18

System clock

Answer 18

A clock that’s built into a computer’s hardware. The hardware clock maintains the time when the computer is powered down. See also software clock.

Question 19

System cron job

Answer 19

A cron job that handles system-wide maintenance tasks, like log rotation or deletion of unused files from /tmp. See also user cron job.

Question 20

User cron job

Answer 20

A cron job created by an individual user to handle tasks for that user, such as running a CPU-intensive job late at night when other users won’t be disturbed by the job’s CPU demands. See also system cron job.

Question 21

usermod

Answer 21

The usermod program closely parallels useradd in its features and parameters. This utility changes an existing account instead of creating a new one, though.

Question 22

UTC

Answer 22

A time closely related to Greenwich Mean Time (GMT).