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/*

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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.

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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.