Rsyslog : Basic Usage2023/07/13

	This is Basic Usage of Rsyslog that is the Log Management Service Daemon.
[1]	According to the configuration when installing Debian OS, though, for example, if Debian is installed without GUI, only selected [Standard system utilities], Rsyslog is not installed, only Jornald manages system logs, so if you need Rsyslog, it needs to install it.

root:~#

apt -y install rsyslog

[2]	Stored rules of logging data are configured in [/etc/rsyslog.conf] and included files.

root@dlp:~#

grep -v -E "^#|^$" /etc/rsyslog.conf

module(load="imuxsock") # provides support for local system logging
module(load="imklog")   # provides kernel logging support
$FileOwner root
$FileGroup adm
$FileCreateMode 0640
$DirCreateMode 0755
$Umask 0022
$WorkDirectory /var/spool/rsyslog
$IncludeConfig /etc/rsyslog.d/*.conf
*.*;auth,authpriv.none          -/var/log/syslog
auth,authpriv.*                 /var/log/auth.log
cron.*                          -/var/log/cron.log
kern.*                          -/var/log/kern.log
mail.*                          -/var/log/mail.log
user.*                          -/var/log/user.log
*.emerg                         :omusrmsg:*

# * how to write rules : (Facility).(Priority)  (Action)
#
# ex : *.info;mail.none;authpriv.none;cron.none /var/log/messages
# ⇒ [syslog] messages of [info] Priority of all Facilities are stored in [/var/log/messages]
# ⇒ but messages of [mail], [authpriv], [cron] Facilities are not stored in [/var/log/messages]
#
# * the [-] that is added at the head of a filename means asynchronous output
#   if [-] is not added, logging data are written with synchronous output

# * Facilities
# kern             :  kernel messages
# auth             :  authentication related messages
# authpriv         :  authentication related messages (private)
# cron             :  cron or at related messages
# mail             :  mail services related messages
# news             :  news related messages
# uucp             :  uucp related messages
# daemon           :  daemon services related messages
# user             :  user level processes related messages
# lpr              :  printer related messages
# syslog           :  internal syslog related messages
# local0 - local7  :  possible to use for custom settings

# * Priorities
# emerg            :  maybe panic level troubles
# alert            :  need to correct immediately more than critical
# crit             :  need to correct immediately
# err              :  common errors, non urgent failures
# warning          :  warning messages
# notice           :  not errors but some unusual events detected
# info             :  normal operational messages
# debug            :  debug information
# none             :  none (not output)

# * if you'd like to store only specified priority messages
# add [=] like follows
# ex : kern.=crit     /dev/console

[2]	To transfer logging data to remote Hosts, Configure like follows.

###### on Syslog Server Host (receives logging data from other Hosts) ######

root@dlp:~#

vi /etc/rsyslog.conf

# line 20-21 : uncomment
line 22 : set allowed hosts to connect

module(load="imtcp")
input(type="imtcp" port="514")
$AllowedSender TCP, 127.0.0.1, 10.0.0.0/24, *.srv.world

root@dlp:~#

systemctl restart rsyslog

###### on Sender Host (sends logging data to Syslog Server Host) ######

root@node01:~#

vi /etc/rsyslog.conf

# add to the end

action(type="omfwd"
       queue.filename="fwdRule_dlp.srv.world"
       queue.maxdiskspace="1g"
       queue.saveonshutdown="on"
       queue.type="LinkedList"
       action.resumeRetryCount="-1"
       Target="dlp.srv.world" Port="514" Protocol="tcp")

# queue.filename               :   queue filename
# queue.maxdiskspace           :   maxdiskspace for queue
# queue.saveonshutdown=on      :   save queue data on disk when system shutdown
# queue.type=LinkedList        :   asynchronous queue which can store 10,000 messages
# action.resumeRetryCount=-1   :   continue to retry sending when syslog server does not respond
# Target=***                   :   specify syslog server Host

root@node01:~#

systemctl restart rsyslog

###### that's OK, verify settings to see logs on syslog server Host ######

root@dlp:~#

tail /var/log/syslog

2023-07-12T23:23:16-05:00 node01 systemd[1]: Stopped rsyslog.service - System Logging Service.
2023-07-12T23:23:16-05:00 node01 systemd[1]: Starting rsyslog.service - System Logging Service...
2023-07-12T23:23:16-05:00 node01 rsyslogd: imuxsock: Acquired UNIX socket '/run/systemd/journal/syslog' (fd 3) from systemd.  [v8.2302.0]
2023-07-12T23:23:16-05:00 node01 rsyslogd: [origin software="rsyslogd" swVersion="8.2302.0" x-pid="965" x-info="https://www.rsyslog.com"] start
2023-07-12T23:23:16-05:00 node01 systemd[1]: Started rsyslog.service - System Logging Service.
2023-07-12T23:23:24-05:00 node01 systemd[1]: Stopping ssh.service - OpenBSD Secure Shell server...
2023-07-12T23:23:24-05:00 node01 systemd[1]: ssh.service: Deactivated successfully.
2023-07-12T23:23:24-05:00 node01 systemd[1]: Stopped ssh.service - OpenBSD Secure Shell server.
2023-07-12T23:23:24-05:00 node01 systemd[1]: Starting ssh.service - OpenBSD Secure Shell server...
2023-07-12T23:23:24-05:00 node01 systemd[1]: Started ssh.service - OpenBSD Secure Shell server.

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