Logs are an invaluable source of information about problems that may arise in your server. Logwatch keeps an eye on your logs for you, flags items that may be of interest, and reports them via email.
Install logwatch
Install logwatch using the following command:
sudo apt install logwatch
You will also need to manually create a temporary directory in order for it to work:
sudo mkdir /var/cache/logwatch
Configure logwatch
Logwatch’s default configuration is kept in /usr/share/logwatch/default.conf/logwatch.conf. However, configuration changes made directly to that file can be overwritten during updates, so instead the file should be copied into /etc and modified there:
sudo cp /usr/share/logwatch/default.conf/logwatch.conf /etc/logwatch/conf/
With your favorite editor, open /etc/logwatch/conf/logwatch.conf. The uncommented lines indicate the default configuration values. First, lets customise some of the basics:
Output = mail
MailTo = me@mydomain.org
MailFrom = logwatch@host1.mydomain.org
Detail = Low
Service = All
This assumes you’ve already set up mail services on host1 that will allow mail to be delivered to your me@mydomain.org address. These emails will be addressed from logwatch@host1.mydomain.org.
The Detail level defines how much information is included in the reports. Possible values are: Low, Medium, and High.
Logwatch will then monitor logs for all services on the system, unless specified otherwise with the Service parameter. If there are undesired services included in the reports, they can be disabled by removing them with additional Service fields. E.g.:
Service = "-http"
Service = "-eximstats"
Next, run logwatch manually to verify your configuration changes are valid:
sudo logwatch --detail Low --range today
The report produced should look something like this:
################### Logwatch 7.4.3 (12/07/16) ####################
Processing Initiated: Fri Apr 24 16:58:14 2020
Date Range Processed: today
( 2020-Apr-24 )
Period is day.
Detail Level of Output: 0
Type of Output/Format: stdout / text
Logfiles for Host:host1.mydomain.org
##################################################################--------------------- pam_unix Begin ------------------------
sudo:
Sessions Opened:
bryce → root: 1 Time(s)---------------------- pam_unix End -------------------------
--------------------- rsnapshot Begin ------------------------
ERRORS:
/usr/bin/rsnapshot hourly: completed, but with some errors: 5 Time(s)
/usr/bin/rsync returned 127 while processing root@host2:/etc/: 5 Time(s)
/usr/bin/rsync returned 127 while processing root@host2:/home/: 5 Time(s)
/usr/bin/rsync returned 127 while processing root@host2:/proc/uptime: 5 Time(s)
/usr/bin/rsync returned 127 while processing root@host3:/etc/: 5 Time(s)
/usr/bin/rsync returned 127 while processing root@host3:/home/: 5 Time(s)
/usr/bin/rsync returned 127 while processing root@host3:/proc/uptime: 5 Time(s)---------------------- rsnapshot End -------------------------
--------------------- SSHD Begin ------------------------
Users logging in through sshd:
bryce:
192.168.1.123 (host4.mydomain.org): 1 time---------------------- SSHD End -------------------------
--------------------- Sudo (secure-log) Begin ------------------------
bryce => root
-------------
/bin/bash - 1 Time(s).---------------------- Sudo (secure-log) End -------------------------
--------------------- Disk Space Begin ------------------------
Filesystem Size Used Avail Use% Mounted on
/dev/sdc1 220G 19G 190G 9% /
/dev/loop1 157M 157M 0 100% /snap/gnome-3-28-1804/110
/dev/loop11 1.0M 1.0M 0 100% /snap/gnome-logs/81
/dev/md5 9.1T 7.3T 1.8T 81% /srv/Products
/dev/md6 9.1T 5.6T 3.5T 62% /srv/Archives
/dev/loop14 3.8M 3.8M 0 100% /snap/gnome-system-monitor/127
/dev/loop17 15M 15M 0 100% /snap/gnome-characters/399
/dev/loop18 161M 161M 0 100% /snap/gnome-3-28-1804/116
/dev/loop6 55M 55M 0 100% /snap/core18/1668
/dev/md1 1.8T 1.3T 548G 71% /srv/Staff
/dev/md0 3.6T 3.5T 84G 98% /srv/Backup
/dev/loop2 1.0M 1.0M 0 100% /snap/gnome-logs/93
/dev/loop5 15M 15M 0 100% /snap/gnome-characters/495
/dev/loop8 3.8M 3.8M 0 100% /snap/gnome-system-monitor/135
/dev/md7 3.6T 495G 3.0T 15% /srv/Customers
/dev/loop9 55M 55M 0 100% /snap/core18/1705
/dev/loop10 94M 94M 0 100% /snap/core/8935
/dev/loop0 55M 55M 0 100% /snap/gtk-common-themes/1502
/dev/loop4 63M 63M 0 100% /snap/gtk-common-themes/1506
/dev/loop3 94M 94M 0 100% /snap/core/9066/srv/Backup (/dev/md0) => 98% Used. Warning. Disk Filling up.
---------------------- Disk Space End -------------------------
###################### Logwatch End #########################
Further reading
- The Ubuntu manpage for logwatch contains many more detailed options.