rsyslog

一、rsyslog是什么

在linux系统中日志可以分为：
（1）klogd：kernel，记录内核相关的日志
（2）syslogd：service，记录应用程序的日志
（3）rsyslog：是CentOS 6以后的系统使用的日志系统，rsyslog是用来管理、记录日志的程序。rsyslog是一个C/S架构的服务，可监听于某套接字，帮其它主机记录日志信息。

二、rsyslog的配置文件/etc/rsyslog.conf

# rsyslog configuration file
 
# For more information see /usr/share/doc/rsyslog-*/rsyslog_conf.html
# If you experience problems, see http://www.rsyslog.com/doc/troubleshoot.html
 
#### MODULES ####
# The imjournal module bellow is now used as a message source instead of imuxsock.
$ModLoad imuxsock # provides support for local system logging (e.g. via logger command)
$ModLoad imjournal # provides access to the systemd journal
#$ModLoad imklog # reads kernel messages (the same are read from journald)
#$ModLoad immark  # provides --MARK-- message capability
 
# Provides UDP syslog reception
#$ModLoad imudp
#$UDPServerRun 514
 
# Provides TCP syslog reception
#$ModLoad imtcp
#$InputTCPServerRun 514
 
 
#### GLOBAL DIRECTIVES ####
 
# Where to place auxiliary files
$WorkDirectory /var/lib/rsyslog
 
# Use default timestamp format
$ActionFileDefaultTemplate RSYSLOG_TraditionalFileFormat
 
# File syncing capability is disabled by default. This feature is usually not required,
# not useful and an extreme performance hit
#$ActionFileEnableSync on
 
# Include all config files in /etc/rsyslog.d/
$IncludeConfig /etc/rsyslog.d/*.conf
# Turn off message reception via local log socket;
# local messages are retrieved through imjournal now.
$OmitLocalLogging on
 
# File to store the position in the journal
$IMJournalStateFile imjournal.state
 
 
#### RULES ####
 
# Log all kernel messages to the console.
# Logging much else clutters up the screen.
#kern.*                                                 /dev/console
 
# Log anything (except mail) of level info or higher.
# Don't log private authentication messages!
*.info;mail.none;authpriv.none;cron.none                /var/log/messages
 
# The authpriv file has restricted access.
authpriv.*                                              /var/log/secure
 
# Log all the mail messages in one place.
mail.*                                                  -/var/log/maillog
 
 
# Log cron stuff
cron.*                                                  /var/log/cron
 
# Everybody gets emergency messages
*.emerg                                                 :omusrmsg:*
 
# Save news errors of level crit and higher in a special file.
uucp,news.crit                                          /var/log/spooler
 
# Save boot messages also to boot.log
local7.*                                                /var/log/boot.log
# ### begin forwarding rule ###
# The statement between the begin ... end define a SINGLE forwarding
# rule. They belong together, do NOT split them. If you create multiple
# forwarding rules, duplicate the whole block!
# Remote Logging (we use TCP for reliable delivery)
#
# An on-disk queue is created for this action. If the remote host is
# down, messages are spooled to disk and sent when it is up again.
#$ActionQueueFileName fwdRule1 # unique name prefix for spool files
#$ActionQueueMaxDiskSpace 1g   # 1gb space limit (use as much as possible)
#$ActionQueueSaveOnShutdown on # save messages to disk on shutdown
#$ActionQueueType LinkedList   # run asynchronously
#$ActionResumeRetryCount -1    # infinite retries if host is down
# remote host is: name/ip:port, e.g. 192.168.0.1:514, port optional
#*.* @@remote-host:514
# ### end of the forwarding rule ###

 三、详解rsyslog的配置文件/etc/rsyslog.conf

日志级别数字越小越紧急，一般运维过程中出现4级就要进行检查注意了

1）debug：调试级别（程序调试信息）
2）info：通知消息（程序的正常输出）
3）notice：注意级别（程序可能有错误）
4）warning：警告级别（警告错误）
5）error：错误级别
6）crit：严重错误级别
7）alter：发出严重报警级别
8）emerg：系统级别故障

记录日志的时候会把本级别以及高于本级别的日志信息都会记录下来。

例子1：

mail.info              info和info以上级别
mail.!info             除了info以外的全部级别
mail.=info             仅仅记录info级别的日志
mail.*                 记录mail设施全部级别的日志
*.info                 记录所以设施的info及其以上级别的日志
mail,auth.info         记录mail和auth两个设施的info及其以上级别的日志
 mail.none              不记录任何级别的日志