syslog-ng Open Source Edition 3.25 - Administration Guide

Error messages

This section describes the most common error messages.

Destination queue full

Destination queue full, dropping messages; queue_len='10000', 
log_fifo_size='10000', count='4', 
persist_name='afsocket_dd_qfile(stream,serverdown:514)' 

Alert unknown CA

SSL error while writing stream; tls_error='SSL routines:ssl3_read_bytes:tlsv1 alert unknown ca'

PEM routines:PEM_read_bio:no start line

Error message:	testuser@thor-x1:~/cert_no_start_line/certs$ openssl x509 -in cert.pem -text unable to load certificate 140178126276248:error:0906D06C:PEM routines:PEM_read_bio:no start line:pem_lib.c:701:Expecting: TRUSTED CERTIFICATE
Description:	The error message is displayed when using Transport Layer Security (TLS). The syslog-ng application uses OpenSSL for TLS and this message indicates that the certificate contains characters that OpenSSL cannot process. The error occurs when the certificate comes from Windows and you want to use it on a Linux-based computer. On Windows, the end of line (EOL) character is different (\r\n) compared to Linux (\n). To verify this, open the certificate in a text editor, for example, MCEdit. Notice the^Mcharacters as shown in the image below: Figure 21: Example of OpenSSL character processing error
Solution:	On Windows, save the certificate using UTF-8, for example, using Notepad++. NOTE: Windows Notepad is not able to save the file in normal UTF-8, even if you select it. In Notepad++, from the menu, selectEncoding. Change the value fromUTF-8-BOMtoUTF-8. Save. On Linux, run dos2unix cert.pem. This will convert the file to a Linux-compatible style. Alternatively, replace the EOL characters in the file manually.

SELinux prevents syslog-ng OSE from using the execmem access on a process

If you are using a recent enough PCRE library, syslog-ng OSE will automatically use the JIT of the regexp engine, which will result in a similar error:

setroubleshoot [21631 ] : SELinux is preventing <syslog-ng path> from using the execmem access on a process. (...)

python [21631 ] : SELinux is preventing <syslog-ng path> from using the execmem access on a process.

To resolve this issue, switch off the PCRE JIT compile function by using the disable-jit flags() option in the given filter or rewrite rule of your configuration.

Best practices and examples

This chapter discusses some special examples and recommendations.

General recommendations

This section provides general tips and recommendations on using syslog-ng. Some of the recommendations are detailed in the sections below:

• Do not base the separation of log messages in different files on the facility parameter. As several applications and processes can use the same facility, the facility does not identify the application that sent the message. By default, the facility parameter is not even included in the log message itself. In general, sorting the log messages into several different files can make finding specific log messages difficult. If you must create separate log files, use the application name.

• Standard log messages include the local time of the sending host, without any time zone information. It is recommended to replace this timestamp with an ISODATE timestamp, because the ISODATE format includes the year and timezone as well. To convert all timestamps to the ISODATE format, include the following line in the syslog-ng configuration file:

  options {ts-format(iso) ; };

• Resolving the IP addresses of the clients to domain names can decrease the performance of syslog-ng. For details, see Using name resolution in syslog-ng.