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Linux+ Guide to Linux Certification, Third Edition. Chapter 10 Common Administrative Tasks. 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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linux guide to linux certification third edition

Linux+ Guide to Linux Certification, Third Edition

Chapter 10

Common Administrative Tasks

objectives
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

Linux+ Guide to Linux Certification, 3e

printer administration the common unix printing system
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

Linux+ Guide to Linux Certification, 3e

printer administration the common unix printing system continued
Printer Administration: The Common UNIX Printing System (continued)
  • cups daemon (cupsd): responsible for printing in CUPS printing system
  • Print job ID: print job’s unique identifier
    • Assigned by cupsd
  • Print queue: directory holding print jobs waiting to be printed
    • Typically /var/spool/cups

Linux+ Guide to Linux Certification, 3e

printer administration the common unix printing system continued1
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.

Linux+ Guide to Linux Certification, 3e

printer administration the common unix printing system continued2
Printer Administration: The Common UNIX Printing System (continued)

Figure 10-1: The print process

Linux+ Guide to Linux Certification, 3e

printer administration the common unix printing system continued3
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

Linux+ Guide to Linux Certification, 3e

managing print jobs
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

Linux+ Guide to Linux Certification, 3e

managing print jobs continued
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

Linux+ Guide to Linux Certification, 3e

managing print jobs continued1
Managing Print Jobs (continued)

Table 10-1: Common options to the lp command

Linux+ Guide to Linux Certification, 3e

managing print jobs continued2
Managing Print Jobs (continued)

Table 10-2: Common options to the lpstatcommand

Linux+ Guide to Linux Certification, 3e

the lpd printing system
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

Linux+ Guide to Linux Certification, 3e

configuring printers
Configuring Printers
  • /etc/cups/cupsd.conf: contains cupsd settings
  • /etc/cups/printers.conf: contains each printer’s 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

Linux+ Guide to Linux Certification, 3e

configuring printers continued
Configuring Printers (continued)

Figure 10-2: The Printer Configuration tool

Linux+ Guide to Linux Certification, 3e

configuring printers continued1
Configuring Printers (continued)

Figure 10-3: Specifying the printer device

Linux+ Guide to Linux Certification, 3e

configuring printers continued2
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

Linux+ Guide to Linux Certification, 3e

configuring printers continued3
Configuring Printers (continued)

Figure 10-4: Selecting the printer manufacturer

Linux+ Guide to Linux Certification, 3e

configuring printers continued4
Configuring Printers (continued)

Figure 10-5: Selecting the printer model

Linux+ Guide to Linux Certification, 3e

configuring printers continued5
Configuring Printers (continued)

Figure 10-6: Completing the creation of a new printer

Linux+ Guide to Linux Certification, 3e

configuring printers continued6
Configuring Printers (continued)

Figure 10-7: Viewing installed printers

Linux+ Guide to Linux Certification, 3e

configuring printers continued7
Configuring Printers (continued)

Figure 10-8: Modifying printer properties

Linux+ Guide to Linux Certification, 3e

configuring printers continued8
Configuring Printers (continued)

Figure 10-9: The Policies section of printer properties

Linux+ Guide to Linux Certification, 3e

configuring printers continued9
Configuring Printers (continued)

Figure 10-10: The Access control section of printer properties

Linux+ Guide to Linux Certification, 3e

configuring printers continued10
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

Linux+ Guide to Linux Certification, 3e

configuring printers continued11
Configuring Printers (continued)

Figure 10-11: Configuring CUPS settings

Linux+ Guide to Linux Certification, 3e

log file administration
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

Linux+ Guide to Linux Certification, 3e

log file administration continued
Log File Administration (continued)

Table 10-3: Common Linux log files found in /var/log

Linux+ Guide to Linux Certification, 3e

the system log daemon
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

Linux+ Guide to Linux Certification, 3e

the system log daemon continued
The System Log Daemon (continued)

Table 10-4: Facilities used by the System Log Daemon

Linux+ Guide to Linux Certification, 3e

the system log daemon continued1
The System Log Daemon (continued)

Table 10-5: Priorities used by the log daemon

Linux+ Guide to Linux Certification, 3e

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

Linux+ Guide to Linux Certification, 3e

managing log files continued
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

Linux+ Guide to Linux Certification, 3e

administering users and groups
Administering Users and Groups
  • Authentication: verify user’s 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

Linux+ Guide to Linux Certification, 3e

administering users and groups continued
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

Linux+ Guide to Linux Certification, 3e

administering users and groups continued1
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

Linux+ Guide to Linux Certification, 3e

administering users and groups continued2
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

Linux+ Guide to Linux Certification, 3e

creating user accounts
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

Linux+ Guide to Linux Certification, 3e

creating user accounts continued
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 user’s password
    • If no arguments, sets current user’s password
    • User accounts must have password set to log on
    • Root user can change any user’s password

Linux+ Guide to Linux Certification, 3e

creating user accounts continued1
Creating User Accounts (continued)

Table 10-6: Common options to the useradd command

Linux+ Guide to Linux Certification, 3e

modifying user accounts
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

Linux+ Guide to Linux Certification, 3e

modifying user accounts continued
Modifying User Accounts (continued)

Table 10-7: Common options to the usermod command

Linux+ Guide to Linux Certification, 3e

deleting user accounts
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

Linux+ Guide to Linux Certification, 3e

managing groups
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

Linux+ Guide to Linux Certification, 3e

managing groups continued
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 user’s primary group
  • Graphical utilities exist to create, modify, and delete user and group accounts

Linux+ Guide to Linux Certification, 3e

managing groups continued1
Managing Groups (continued)

Figure 10-13: Configuring users and groups within a desktop environment

Linux+ Guide to Linux Certification, 3e

summary
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

Linux+ Guide to Linux Certification, 3e

summary continued
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

Linux+ Guide to Linux Certification, 3e

summary continued1
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

Linux+ Guide to Linux Certification, 3e

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