CIS 193A – Lesson3CIS 193A – Lesson3
Vigilance!Logging & Monitoring
SyslogLogrotate
LogwatchAccounting
CIS 193A – Lesson3
Focus Question
What tools does Linux provide for organizing and making useful sense of logged output?
CIS 193A – Lesson3
The Syslog Utility
• Daemons: syslogd and klogd• Configuration: /etc/syslog.conf• Log files: /var/log/messages
secure maillog cron spooler boot.log
CIS 193A – Lesson3
Syslog Facilities
Syslog categorizes messages into the following “facilities”:– authpriv - local0– cron - local1– daemon - local2– ftp - local3– kern - local4– lpr - local5– mail - local6– news - local7– syslog,user,uucp
CIS 193A – Lesson3
Syslog – Levels of Logging• Syslog organizes messages within a facility
according to level of importance:– emerg– alert– crit– err– warning– notice– info– debug
• Logging at one of these levels, logs all messages at that level and above
CIS 193A – Lesson3
Log Files
• Syslog logs to files, but in UNIX, everything is a file!– Regular files in /var/log/– Terminal screens: /dev/console– Another program: | program– A remote syslog server: @servername
CIS 193A – Lesson3
The logger Command
The logger command allows shell scripts to use the syslog facility:
logger [-t tag] –p facility.level “message”
The logger command will also read the message to log from stdin:
echo “message” | logger –p facility.level
Often used in service init scripts.
CIS 193A – Lesson3
The logrotate Facility
Customizable, pluggable log-rotating system.
• Executable: /usr/sbin/logrotate activated by cron on a daily basis
• Configuration: /etc/logrotate.conf and /etc/logrotate.d/*
logrotate.conf contains global settings, and individual services add their settings to logrotate.d
CIS 193A – Lesson3
Features of logrotate
• Rotates any file through a series of predefined extensions: .1, .2, … .n
• You configure the frequency.• May compress files as well.• May rotate based on size of file.• May mail you the last file of series
rather than delete.
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Configuration File Syntax
Filename [,filename] { rotate n # n is number of copies weekly # frequency: daily, monthly compress mail email size nk postrotate
command to restart logging service endscript}
CIS 193A – Lesson3
logwatch
CIS 193A – Lesson3
The logwatch Service
Customizable, pluggable log-monitoring system written in perl. Goes through your logs for a given period of time and make a report in the areas that you wish with the detail that you wish.
• Executable: /usr/sbin/logwatch• Configuration: /etc/logwatch
/usr/share/logwatch/default.conf/*
CIS 193A – Lesson3
logwatch Features
• Will analyze logfiles by service.• Supports three levels of detail.• Analyzes today’s, yesterday’s or
historical data.• Mails summary of analysis to root
account.• Extensible, drop-in scripts and
configuration files.
CIS 193A – Lesson3
Logwatch Examples
Although logwatch is normally run from cron just before a logrotate is done, you can run the command from the command line:
logwatch --range all –-detail high –-service sshd –-print
Logwatch –-range yesterday –-detail low –-logfile secure
CIS 193A – Lesson3
Process Accounting
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A Suite of Utilities
• As a service: psacct– logs to /var/account/pacct
• As a client: lastcomm• Other clients:
– ac– sa– last, lastb
CIS 193A – Lesson3
Review
CIS 193A – Lesson3
Focus Question
What tools does Linux provide for organizing and making useful sense of logging output?
Syslog allows you to organize log messages from different facilities according to their severity level. Logrotate prevents the log files from getting too large, and logwatch summarizes information from the logs.