Linux Guide to Linux Certification, Third Edition

1
Linux Guide to Linux Certification, Third Edition

• Chapter 10
• Common Administrative Tasks

2
Objectives

• Set up, manage, and print to printers on a Linux
  system
• Understand the purpose of log files and how they
  are administered
• Create, modify, manage, and delete user and group
  accounts

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Printer Administration The Common UNIX Printing
System

• Common Unix Printing System (CUPS) most common
  printing system used on Linux
• Print job set of information sent to a printer
  at the same time
• Can consist of a file, a set of files, or the
  output of a command
• lp command sends a print job to a printer

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Printer Administration The Common UNIX Printing
System (continued)

• cups daemon (cupsd) responsible for printing in
  CUPS printing system
• Print job ID print jobs unique identifier
• Assigned by cupsd
• Print queue directory holding print jobs waiting
  to be printed
• Typically /var/spool/cups

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Printer Administration The Common UNIX Printing
System (continued)

• Printer can accept or reject request to print
• If rejected, CUPS gives an error message
• Spooling or queuing accepting print jobs into a
  print queue
• Printing sending print jobs from print queue to
  a printer
• Occurs if the printer is enabled, cupsd removes
  copy of print job from the print queue.

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Printer Administration The Common UNIX Printing
System (continued)
Figure 10-1 The print process
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Printer Administration The Common UNIX Printing
System (continued)

• lpstat command with t (total) option, lists all
  printers and their status
• cupsaccept, cupsreject, cupsenable, and
  cupsdisable commands manipulate status of a
  printer
• -r option used to specify reason for cupsdisable
  and cupsreject commands

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Managing Print Jobs

• lp d command print to a specified printer
• If d option omitted, prints to default printer
• lpoptions d command set default printer
• Each user can set his own default printer
• Add name of the default printer to .lpoptions
  file in home directory
• Use PRINTER or LPDEST variable

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Managing Print Jobs (continued)

• lp command accepts information from stdin
• lpstat command can list print jobs in queue for a
  printer
• cancel command remove print jobs from print
  queue
• Receives print job IDs as arguments
• -u option remove all the jobs sent by specified
  user
• lpadmin command perform printer administration
• e.g., restrict specific user access to specific
  printers

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Managing Print Jobs (continued)
Table 10-1 Common options to the lp command
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Managing Print Jobs (continued)
Table 10-2 Common options to the lpstat command
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The LPD Printing System

• Line Printer Daemon (LPD) printing system used
  on older Linux systems
• lpr command send documents to a print queue
• lpc command view status of printers
• lpq command view print jobs in print queue
• lprm command remove print jobs
• CUPS contains versions of the lpr, lpc, lpq, and
  lprm commands

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Configuring Printers

• /etc/cups/cupsd.conf contains cupsd settings
• /etc/cups/printers.conf contains each printers
  configuration information
• Printer Configuration tool used to edit printer
  and cupsd setting files and thus configure
  printers
• Activated using the system-config-printer command
  in a desktop environment
• e.g., add new printers

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Configuring Printers (continued)
Figure 10-2 The Printer Configuration tool
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Configuring Printers (continued)
Figure 10-3 Specifying the printer device
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Configuring Printers (continued)

• For local printers that do not support PnP, must
  specify the Uniform Resource Identifier (URI) for
  the device
• Within Printer Configuration tool you can
• Give a printer a name to identify it within
  programs and commands
• Specify printer location and description
• Modify printer properties
• Manage the status of the printer, share it using
  IPP, choose an error action, and configure banner
  pages

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Configuring Printers (continued)
Figure 10-4 Selecting the printer manufacturer
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Configuring Printers (continued)
Figure 10-5 Selecting the printer model
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Configuring Printers (continued)
Figure 10-6 Completing the creation of a new
printer
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Configuring Printers (continued)
Figure 10-7 Viewing installed printers
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Configuring Printers (continued)
Figure 10-8 Modifying printer properties
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Configuring Printers (continued)
Figure 10-9 The Policies section of printer
properties
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Configuring Printers (continued)
Figure 10-10 The Access control section of
printer properties
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Configuring Printers (continued)

• To apply standard printer properties to several
  printers on a system, create printer class
• Apply the properties to the printer class
• Printer Configuration tool allows configuration
  of the properties of CUPS daemon
• Add shared network printers
• Share printers on the system
• Remotely create and manage printers

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Configuring Printers (continued)
Figure 10-11 Configuring CUPS settings
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Log File Administration

• Log file file containing system information
• Typically recorded during daemon activity
• Information includes error messages
• /var/log contains most log files
• Many programs store log files in subdirectories

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Log File Administration (continued)
Table 10-3 Common Linux log files found in
/var/log
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The System Log Daemon

• System log daemon (syslogd) central handling of
  logging system events
• Creates /dev/log socket for system processes to
  write to
• Writes to appropriate log file using
  /etc/rsyslog.conf file
• Entries indicate facility and priority
• Facility area of system that information is
  gathered from
• Priority importance of system information

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The System Log Daemon (continued)
Table 10-4 Facilities used by the System Log
Daemon
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The System Log Daemon (continued)
Table 10-5 Priorities used by the log daemon
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Managing Log Files

• Log files can take up unnecessary space
• Clear contents occasionally
• Print copy for records
• Use gt redirection symbol to clear log file
• Use cron daemon for repetitive clearing
• Do not remove log files
• Permissions and ownership will be removed

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Managing Log Files (continued)

• logrotate command back up and clear log files
• Compress old log files and save under new name
• /etc/logrotate.conf used by logrotate utility
• Specifies rotation parameters for log files

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Administering Users and Groups

• Authentication verify users identity
• Compare username and password to system database
• Database containing user account information
  typically consists of two files
• /etc/passwd user account information
• /etc/shadow encrypted password and expiration
  information
• pwconv command convert system to use an
  /etc/shadow file for encrypted password storage

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Administering Users and Groups (continued)

• pwunconv command revert back to using an
  /etc/passwd file only
• User Identifier (UID) unique user ID for each
  user
• Group Identifier (GID) primary group ID for each
  user
• Primary group group owner for all files created
  by a user
• General Electric Comprehensive Operating System
  (GECOS) text description of the user
• Typically left blank

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Administering Users and Groups (continued)

• Root user usually listed at top of /etc/passwd
  file
• Next are listed system daemons
• Password field differs in the two files
• /etc/shadow contains encrypted password
• /etc/passwd contains an x character
• lastchange date of most recent password change
• Number represents number of days since January 1,
  1970

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Administering Users and Groups (continued)

• Passwords often set to expire at certain
  intervals
• Intervals specified in /etc/shadow
• Minimum number of days before changing password
• Maximum number of days to use password
• Number of days before password expiration in
  which user is warned to change password
• /etc/group file Lists all groups and their
  members
• Allows users to belong to multiple groups
• Password field usually contains an x

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Creating User Accounts

• useradd command add new user accounts
• Most new user information comes from two files
• /etc/login.defs
• E-mail location, password expiration, minimum
  password length, range of UIDs and GIDs
• /etc/default/useradd
• Default primary group, home directory location,
  password expiration info, shell, skeleton
  directory

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Creating User Accounts (continued)

• Skeleton directory contains environment files to
  copy to new users home directories
• Usually /etc/skel
• Override default parameters by specifying options
  to useradd command
• passwd command set a users password
• If no arguments, sets current users password
• User accounts must have password set to log on
• Root user can change any users password

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Creating User Accounts (continued)
Table 10-6 Common options to the useradd command
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Modifying User Accounts

• usermod command modify user account information
• chage command modify password expiration
  information
• Locking an account make an account temporarily
  unusable
• Alter password information
• Use l or L options of passwd command
• chsh command change a valid shell to an invalid
  shell

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Modifying User Accounts (continued)
Table 10-7 Common options to the usermod command
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Deleting User Accounts

• userdel command remove user accounts
• Specify user name as argument
• When an account is deleted, files previously
  owned by the user become owned by a number
  representing UID of deleted user
• Next user with that UID will own the files

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Managing Groups

• Can add groups by editing /etc/group file
• groupadd command add a group to the system
• groupmod command modify GID name of a group on
  the system
• groupdel command remove a group from the system

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Managing Groups (continued)

• groups command list groups that user belongs to
• id command list GIDs of groups that a user
  belongs to
• newgrp command temporarily change users primary
  group
• Graphical utilities exist to create, modify, and
  delete user and group accounts

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Managing Groups (continued)
Figure 10-13 Configuring users and groups within
a desktop environment
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Summary

• Print jobs are spooled to a print queue before
  being printed to a printer
• You can configure spooling or printing by using
  the cupsaccept, cupsreject, cupsenable, and
  cupsdisable commands
• Print jobs are created using lp, can be viewed in
  the queue using lpstat, and are removed from the
  queue using cancel

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Summary (continued)

• Create local and remote printers using Printer
  Configuration tool or by modifying
  /etc/cups/printers.conf
• Most log files in Linux are stored in /var/log
• System events are typically logged to files by
  the System Log Daemon
• Log files should be cleared or rotated over time
  to save disk space
• User and group account information is typically
  in /etc/passwd, /etc/shadow, and /etc/group

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Summary (continued)

• Use the useradd command to create users and the
  groupadd command to create groups
• All users must have a valid password before
  logging in to a Linux system
• Users can be modified with usermod, chage, chfn,
  chsh, and passwd commands, and groups can be
  modified using groupmod command
• The userdel and groupdel commands remove users
  and groups from the system, respectively