Syslog

Per default VyOSs has minimal syslog logging enabled which is stored and rotated locally. Errors will be always logged to a local file, which includes local7 error messages, emergency messages will be sent to the console, too.

To configure syslog, you need to switch into configuration mode.

Logging

Syslog supports logging to multiple targets, those targets could be a plain file on your VyOS installation itself, a serial console or a remote syslog server which is reached via IP UDP/TCP.

Console

set system syslog console facility <keyword> level <keyword>

Log syslog messages to /dev/console, for an explanation on {ref}`syslog_facilities` keywords and {ref}`syslog_severity_level` keywords see tables below.

Custom File

set system syslog file <filename> facility <keyword> level <keyword>

Log syslog messages to file specified via <filename>, for an explanation on {ref}`syslog_facilities` keywords and {ref}`syslog_severity_level` keywords see tables below.

set system syslog file <filename> archive size <size>

Syslog will write <size> kilobytes into the file specified by <filename>. After this limit has been reached, the custom file is “rotated” by logrotate and a new custom file is created.

set system syslog file <filename> archive file <number>

Syslog uses logrotate to rotate logiles after a number of gives bytes. We keep as many as <number> rotated file before they are deleted on the system.

Remote Host

Logging to a remote host leaves the local logging configuration intact, it can be configured in parallel to a custom file or console logging. You can log to multiple hosts at the same time, using either TCP or UDP. The default is sending the messages via port 514/UDP.

set system syslog host <address> facility <keyword> level <keyword>

Log syslog messages to remote host specified by <address>. The address can be specified by either FQDN or IP address. For an explanation on {ref}`syslog_facilities` keywords and {ref}`syslog_severity_level` keywords see tables below.

set system syslog host <address> facility <keyword> protocol <udp|tcp>

Configure protocol used for communication to remote syslog host. This can be either UDP or TCP.

set system syslog vrf <name>

Specify name of the {abbr}`VRF (Virtual Routing and Forwarding)` instance.

TLS-encrypted remote logging

VyOS supports TLS-encrypted remote logging over TCP to ensure secure transmission of syslog data to remote syslog servers.

Prerequisites: Before configuring TLS-encrypted remote logging, ensure you have:

A valid remote syslog server address.
Valid CA and client certificates uploaded to the local PKI storage.

The remote syslog transport protocol is set to TCP:

set system syslog remote <address> protocol tcp

Note

TLS-encrypted remote logging is not supported over UDP.

set system syslog remote <address> tls

Enable TLS-encrypted remote logging.

set system syslog remote <address> tls ca-certificate <ca_name>

Configure the {abbr}`CA (Certificate Authority)` certificate.

The syslog client uses the {abbr}`CA (Certificate Authority)` certificate to verify the identity of the remote syslog server.

The {abbr}`CA (Certificate Authority)` certificate is required for all authentication modes except anon.

set system syslog remote <address> tls certificate <cert_name>

Configure the client certificate.

The remote syslog server uses the client certificate to verify the identity of the syslog client.

The client certificate is required if the remote syslog server enforces client certificate verification.

set system syslog remote <address> tls auth-mode <anon | fingerprint | certvalid | name>

Configure the authentication mode.

The authentication mode defines how the syslog client verifies the syslog server’s identity.

The following authentication modes are available:

anon (default): Allows encrypted connections without verifying the syslog server’s identity. This mode is not recommended, as it is vulnerable to {abbr}`MITM (Man-in-the-Middle)` attacks.
fingerprint: Verifies the server’s certificate fingerprint against the value preconfigured with:
```
set system syslog remote <address> tls permitted-peer <peer>
```
certvalid: Verifies the server certificate is signed by a trusted {abbr}`CA (Certificate Authority)`, skipping {abbr}`CN (Common Name)` check.
name: Verifies that:
- The server’s certificate is signed by a trusted {abbr}`CA (Certificate Authority)`.
- The {abbr}`CN (Common Name)` in the certificate matches the value preconfigured with:
```
set system syslog remote <address> tls permitted-peer <peer>
```
This is a recommended secure mode for production environments.

set system syslog remote <address> tls permitted-peer <peer>

Configure the peer certificate identifiers.

The certificate identifier format depends on the authentication mode:

fingerprint: Enter the expected certificate fingerprints (SHA-1 or SHA-256).
name: Enter the expected certificate {abbr}`CNs (Common Names)`.

For anon and certvalid authentication modes, certificate identifiers are not required.

Examples:

# Example of 'anon' authentication mode
set system syslog host 10.10.2.3 facility all level debug
set system syslog host 10.10.2.3 port 6514
set system syslog host 10.10.2.3 protocol tcp
set system syslog host 10.10.2.3 tls auth-mode anon
# or just use 'set system syslog host 10.10.2.3 tls'

# Example of 'certvalid' authentication mode
set system syslog host elk.example.com facility all level debug
set system syslog host elk.example.com port 6514
set system syslog host elk.example.com protocol tcp
set system syslog host elk.example.com tls ca-certificate my-ca
set system syslog host elk.example.com tls auth-mode certvalid

# Example of 'fingerprint' authentication mode
set system syslog host syslog.example.com facility all level debug
set system syslog host syslog.example.com port 6514
set system syslog host syslog.example.com protocol tcp
set system syslog host syslog.example.com tls ca-certificate my-ca
set system syslog host syslog.example.com tls auth-mode fingerprint
set system syslog host syslog.example.com tls permitted-peer 'SHA1:10:C4:26:...'

# Example of 'name' authentication mode
set system syslog host graylog.example.com facility all level debug
set system syslog host graylog.example.com port 6514
set system syslog host graylog.example.com protocol tcp
set system syslog host graylog.example.com tls ca-certificate my-ca
set system syslog host graylog.example.com tls certificate syslog-client
set system syslog host graylog.example.com tls auth-mode name
set system syslog host graylog.example.com tls permitted-peer 'graylog.example.com'

Security Notes

Always prefer auth-mode name for secure deployments, as it ensures both CA trust and server hostname validation.
anon mode should only be used for testing, because it does not authenticate the server.
Ensure private keys are stored and managed exclusively in the PKI system.

Local User Account

set system syslog user <username> facility <keyword> level <keyword>

If logging to a local user account is configured, all defined log messages are display on the console if the local user is logged in, if the user is not logged in, no messages are being displayed. For an explanation on {ref}`syslog_facilities` keywords and {ref}`syslog_severity_level` keywords see tables below.

Facilities

List of facilities used by syslog. Most facilities names are self explanatory. Facilities local0 - local7 common usage is f.e. as network logs facilities for nodes and network equipment. Generally it depends on the situation how to classify logs and put them to facilities. See facilities more as a tool rather than a directive to follow.

Facilities can be adjusted to meet the needs of the user:

Facility Code	Keyword	Description
	all	All facilities
0	kern	Kernel messages
1	user	User-level messages
2	mail	Mail system
3	daemon	System daemons
4	auth	Security/authentication messages
5	syslog	Messages generated internally by syslogd
6	lpr	Line printer subsystem
7	news	Network news subsystem
8	uucp	UUCP subsystem
9	cron	Clock daemon
10	security	Security/authentication messages
11	ftp	FTP daemon
12	ntp	NTP subsystem
13	logaudit	Log audit
14	logalert	Log alert
15	clock	clock daemon (note 2)
16	local0	local use 0 (local0)
17	local1	local use 1 (local1)
18	local2	local use 2 (local2)
19	local3	local use 3 (local3)
20	local4	local use 4 (local4)
21	local5	local use 5 (local5)
22	local6	use 6 (local6)
23	local7	local use 7 (local7)

Severity Level

Value	Severity	Keyword	Description
		all	Log everything
0	Emergency	emerg	System is unusable - a panic condition
1	Alert	alert	Action must be taken immediately - A condition that should be corrected immediately, such as a corrupted system database.
2	Critical	crit	Critical conditions - e.g. hard drive errors.
3	Error	err	Error conditions
4	Warning	warning	Warning conditions
5	Notice	notice	Normal but significant conditions - conditions that are not error conditions, but that may require special handling.
6	Informational	info	Informational messages
7	Debug	debug	Debug-level messages - Messages that contain information normally of use only when debugging a program.

Display Logs

show log [all | authorization | cluster | conntrack-sync | …]

Display log files of given category on the console. Use tab completion to get a list of available categories. Thos categories could be: all, authorization, cluster, conntrack-sync, dhcp, directory, dns, file, firewall, https, image lldp, nat, openvpn, snmp, tail, vpn, vrrp

If no option is specified, this defaults to all.

show log image <name> [all | authorization | directory | file <file name> | tail <lines>]

Log messages from a specified image can be displayed on the console. Details of allowed parameters:

all	Display contents of all master log files of the specified image
authorization	Display all authorization attempts of the specified image
directory	Display list of all user-defined log files of the specified image
file <file name>	Display contents of a specified user-defined log file of the specified image
tail	Display last lines of the system log of the specified image
<lines>	Number of lines to be displayed, default 10

When no options/parameters are used, the contents of the main syslog file are displayed.

Hint

Use show log | strip-private if you want to hide private data when sharing your logs.

Delete Logs

delete log file <text>

Deletes the specified user-defined file <text> in the /var/log/user directory

Note that deleting the log file does not stop the system from logging events. If you use this command while the system is logging events, old log events will be deleted, but events after the delete operation will be recorded in the new file. To delete the file altogether, first delete logging to the file using system syslog Custom File command, and then delete the file.