06 System Administration Tools - altair.pw HAT LINUX TUTORIAL/RH1… · Certification System Administration Tools. Copyright © 2003 Red Hat, Inc. 1 Rev RH133-9.0-1. Copyright ©

Certification

System Administration Tools

Copyright © 2003 Red Hat, Inc.

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Rev RH133-9.0-1

UNIT 6

System Administration Tools


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UNIT 6: Objectives

Upon completion of this unit you should be able to:

• Configure printing• Perform task automation with at and cron• Configure system logging• Monitor system resources and activities• Perform backup and restore


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UNIT 6: Agenda

• Printing• Task Automation• System Logging• System Monitoring• Backup and Restore


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Alternatives

• Multiple services in the distribution may provide the same functions

• alternatives allows the selection of which service is used through a generic name

• Generic name is a link to a link in/etc/alternatives/

• Only the links in /etc/alternatives/ are modified

• Related links can be arranged in a link group

• Master link and slave links

• Link groups have two modes, auto and manual


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Using alternatives• Systems with alternatives available

• print: /usr/bin/lpr.cups and /usr/bin/lpr.LPRng• mta: /usr/sbin/sendmail.sendmail and /usr/sbin/sendmail.postfix

• alternatives displays and sets link groups• alternatives --display name• alternatives --auto name• alternatives --config name• alternatives --set name path

• redhat-switch-printer{-nox}• redhat-switch-mail{-nox}


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Print System User Interface• BSD Interface

• lpr, lpq, lprm• System V Interface

• lp, lpstat, cancel• Print Queue Specification

• lpr -P printer• lp -d printer• $PRINTER, $LPDEST


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CUPS Overview• New IPP protocol based on HTTP/1.1

• Web administration interface on port 631• Can communicate with LPD print servers

• System V and BSD command interfaces• Classes support automatic job redirection and printer

pooling• Authentication by user/host/digital certificate• Log files in web server Common Log Format• Print Queue Design

• program --> lp --> cupsd --> filter --> printer


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CUPS Configuration Files

• /etc/cups/cupsd.conf• cupsd server configuration file• similar syntax to Apache httpd.conf file

• /etc/cups/printers.conf• print queue configuration file• automatically generated by lpadmin or web

administration interface


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CUPS Queue Management• lpadmin commands

• Add printer:lpadmin -p PRINTER -E -v DEV

• Set system default printer:lpadmin -d PRINTER

• Delete printer: lpadmin -x PRINTER• Web interface: http://localhost:631/

• To authenticate, user must be a member of theSystemGroup (sys by default) listed in /etc/cups/cupsd.conf

• Connection is not encrypted


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LPRng Overview• LPRng Features

• RFC1167 (LPD) compliant• BSD and System V command interfaces• Dynamic Job Redirection• Printer Pool Support

• Print Queue Design• program --> lpr --> lpd --> filter --> printer

• configuration files:• /etc/printcap, /etc/printcap.local• lpd.conf• lpd.perms


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/etc/printcap and redhat-config-printer• /etc/printcap

• print queue configuration file for LPRng• automatically generated by redhat-config-printer

• redhat-config-printer, redhat-config-printer-tui

• /etc/printcap.local• for manually managed printcap entries• automatically appended to /etc/printcap

• checkpc


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LPRng Queue Management• lpc commands

• status, abort, redo, kill• queue state commands: enable, disable, start, stop, up, down

• scheduling commands: topq, hold, release• queue management: redirect, class

• print filters• printconf (foomatic)


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Task Automation

• Red Hat Linux provides three facilities• at - Execute a task at a specific time• cron - Execute tasks at scheduled intervals• anacron – Run tasks after prescribed intervals

have passed


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Using at

• Useful for schedule a single future event• Use cron instead for recurring events

• Use atq, atrm to manage jobs• atq - lists pending jobs (and job IDs)• atrm - deletes pending job by job ID

• Example:$ at 6:00at> mail joe < joe.msg


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Controlling Access to at

• Use access files• /etc/at.allow• /etc/at.deny

• Contains usernames to whom access is allowed or denied


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Using cron

• Schedules recurring events• Use crontab to edit, install, and view job

schedules• Syntax

• crontab [-u user] file• crontab [-l|-r|-e]


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crontab Format

30 6 * * 0 /home/joe/mailmom.sh

CommandDay of Week (0-6)Month (1-12)Day Hour (0-23)Minute (0-59)


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System crontab Files• Different format than user crontab files• Master crontab file /etc/crontab runs

executables in• /etc/cron.hourly• /etc/cron.daily• /etc/cron.weekly• /etc/cron.monthly

• /etc/cron.d/ directory contains additional system crontab files


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Controlling Access to cron

• Restrict / allow user access to cron• /etc/cron.allow• /etc/cron.deny

• Contains usernames to allow / deny access for


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Using anacron

• Does not assume machine is powered at all times.

• Not a daemon like cron• Useful on laptops, workstations


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The anacrontab file

• Schedules anacron tasks• /etc/anacrontab• Format different from crontab

7 10 weekly.tasks /opt/bin/weekly.sh

CommandLabelDelay (min)Interval (days)


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Using tmpwatch

• Cleans old files out of specified directories• Useful for keeping /tmp directory from filling

up• tmpwatch is run daily in /etc/cron.daily


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System Log Configuration

• Centralized system logging• Logging daemons

•Syslogd•klogd


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System Log Configuration (cont.)

• /etc/syslog.conf• Configures system logging

• /etc/sysconfig/syslog• Sets switches used when starting syslogd and klogd from the System V startup script

• /var/log/messages• File where logged messages are written


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System Logging

• /var/log/dmesg• Kernel boot messages

• /var/log/messages• Standard system error messages

• /var/log/maillog• Mail system messages

• dmesg• prints contents of kernel ring buffer


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System Logging - cont

• /var/log/xferlog• FTP transfers using wu-ftpd• vsftpd uses /var/log/vsftpd.log

• /var/log/secure• Security information • System login and network connection info


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Maintaining Logs• Maintain with logrotate

• Keeps log files from getting too large• Keeps filesystem from filling up

• logrotate is run daily in /etc/cron.daily

• Highly configurable• Configure all logs in /etc/logrotate.conf• Configure individual log files in files within /etc/logrotate.d


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Monitoring Logs

• Monitor with logwatch• Helps catch problem issues• Detects suspicious behavior

• logwatch is run daily in /etc/cron.daily• Configured in /etc/log.d/conf/logwatch.conf

• Sends nightly email report• Other tools


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Managing whatis

• The whatis command relies on a database• Database updated with makewhatis

• Updated daily via /etc/cron.daily script


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System Monitoring and Process Control

• top, gnome-system-monitor - display snapshotof processes

• procinfo - displays information from /proc• vmstat - reports virtual memory stats• iostat - lists information on resource usage,

including I/O statistics• free - summary of system memory usage• renice - change priority of a process• kill - send system signal to a process


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Backup to Tape

• Red Hat Linux supports many tape devices• IDE tape devices

• /dev/[n]ht0, /dev/[n]ht1, etc.• SCSI tape devices (i.e., DDS, DLT)

• /dev/[n]st0, /dev/[n]st1, etc.• Floppy tape devices

• /dev/[n]rft0, /dev/[n]rft1, etc.


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Controlling Tape Drives

• Use the mt utility to control tape drive• mt -f /dev/st0 rewind (Rewind)• mt -f /dev/st0 fsf 50 (Position)• mt -f /dev/st0 offline (Eject)• mt -f /dev/st0 erase (Erase)• mt -f /dev/st0 rewoff (Rewind, Eject)


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Using tar• Originally used for tapes• Also used for creating archive files• Parameter syntax

• Use x to extract from archive• Use c to create from archive• Use v for verbose output

• Example• tar xvf archive.tar


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Using dump/restore

• Back up and restore ext2/3 filesystems• Does not work with other filesystems

• Can do full or incremental backups• Example

• dump -0u -f /dev/nst0 /dev/hda2• restore -rf /dev/nst0


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Using cpio

• Similar to tar• Does not recurse directories by itself• Piping output from find into cpio is common

• Example• find /tmp | cpio -ocv > /dev/nst0


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Remote Backups

• dump and tar can use rmt (remote tape mgr)• dump -0uf joe@svr:/dev/nst0 /home• Use user@host:path format to specify the

remote user, host, and device.• dump can use ssh for secure backups when RSH

environment variable is set to ssh• i.e., ($ RSH=ssh)


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Other Backup Software

• Higher-level applications for tape backup include:• Amanda

• Highly-scalable command-line client-server archiver included with Red Hat Linux

• Commercial applications• Arkeia, Bru, Veritas (client), UNiBACK, ArcServe


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End of Unit 6

• Questions and answers• Summary

• Configuring Printing• Task Automation• Configuring System Logging• Performing System Monitoring• Backup and Restore

Documents

06 System Administration Tools - altair.pw HAT LINUX TUTORIAL/RH1… · Certification System Administration Tools. Copyright © 2003 Red Hat, Inc. 1 Rev RH133-9.0-1. Copyright ©