System Logging - Revision history

Mgloff at 22:40, 11 June 2019

2019-06-11T22:40:42Z

Mgloff at 21:47, 13 July 2017

2017-07-13T21:47:35Z

Awichmann at 16:20, 8 June 2016

2016-06-08T16:20:18Z

Mdean: Fixed source formatting issue.

2015-11-20T19:13:25Z

Fixed source formatting issue.

Rossi at 21:48, 18 November 2015

2015-11-18T21:48:28Z

Kyoungmeyer at 21:11, 18 November 2015

2015-11-18T21:11:40Z

Mdean: Last minute addition while waiting for a reviewer.

2015-11-18T20:49:45Z

Last minute addition while waiting for a reviewer.

Mdean: Ready for review.

2015-11-18T18:58:12Z

Ready for review.

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2015-11-18T00:13:27Z

Almost finished. Almost.

Mdean: Checking page in while switching tasks.

2015-11-17T22:19:20Z

Checking page in while switching tasks.

@@ Line 134: / Line 134: @@
 <!-- /*********************************************************************************************************/ -->
 {{:Templateimpl:using | initials=MD | title=System Logging | desc=The page describes how to system log. | project=OE 5.0 }}
-EMAC OE Linux 5.X uses Busybox's syslog daemon, <code>syslogd</code>, by default.  However, the <code>syslog-ng</code> package can be installed to provide a much more capable system logging daemon, when needed.
+EMAC OE Linux 5.X uses Busybox's built-in version of syslog daemon, <code>syslogd</code>, by default.  However, the <code>syslog-ng</code> package can be installed to provide a much more capable system logging daemon, when needed.
 ====About====
@@ Line 151: / Line 147: @@
 ====Working With====
-The Busybox syslog daemon is configured, by default, to log to files in the RAMDISK mounted on <code>/var/log/</code>.  The files contained in this directory will be capped in size and rotated according to the configuration of the syslog daemon.
+The syslog daemon is configured, by default, to log to a shared memory buffer. The messages are displayed with the <code>logread</code> utility.
 The standard <code>/etc/syslog-startup.conf</code> configuration is shown below:
@@ Line 161: / Line 155: @@
 # /etc/init.d/syslog[.busybox] to set syslog configuration at start time.
-DESTINATION=file                # log destinations (buffer file remote)
+DESTINATION=buffer                # log destinations (buffer file remote)
 LOGFILE=/var/log/messages       # where to log (file)
 REMOTE=loghost:514              # where to log (syslog remote)
@@ Line 184: / Line 178: @@
 : The <code>LOGFILE</code> parameter specifies the location of the logfile which should be used with the <code>file</code> destination.
 ;REMOTE
-: The <code>REMOTE</code> parameter specifies the host and port to which to send remote log messages.  The two part format for this variable provides the destination host followed by the destination port number, with a colon as the delimiter between the two.  The destination may be specified as a hostname, or as an IP address.  The destination port number should be the port on which the remote syslog server listens.
+: The <code>REMOTE</code> parameter specifies the host and port to which to send remote log messages.  The two part format for this variable provides the destination host followed by the destination port number, with a colon as the delimiter between the two.  The destination may be specified as a hostname, or as an IP address.  The destination port number should be the port on which the remote syslog server listens. Port 514 is the default syslog port. A syslog collector server will need to be installed and set up in order to log remotely.
 {{note | If the destination is specified as a hostname, it is best to create an entry in <code>/etc/hosts</code> for the hostname so that it will resolve to an IP address even if there is a problem with the DNS servers.}}
@@ Line 303: / Line 297: @@
 {{clop}}
-{{cliop | pwd=/var/log |<nowiki>function genseq() { logfn=$1; max=$2; for i in $(seq $max -1 0); do printf "${logfn}.${i} "; done;</nowiki>}}<nowiki>
+{{cliop | pwd=/var/log |<nowiki>function genseq() { logfn=$1; max=$2; for i in $(seq $max -1 0); do printf "${logfn}.${i} "; done; printf "$logfn\n"; }</nowiki>}}
 {{closp}}

@@ Line 581: / Line 581: @@
 <!-- /*********************************************************************************************************/ -->
 {{:Templateimpl:moreinfo | initials=MD | title=System Logging | desc=The page describes how to system log. | project=OE 5.0 }}
-* [[Install_the_EMAC_SDK | Installing the EMAC SDK]]
+* [[Installing_EMAC_OE_5.0_SDK | Installing the EMAC SDK]]
 {{:Templateimpl:whatnext | initials=MD | title=System Logging | desc=The page describes how to system log. | project=OE 5.0 }}
 * [[Opkg | Working With the OPKG Package Manager]]

@@ Line 134: / Line 134: @@
 <!-- /*********************************************************************************************************/ -->
 {{:Templateimpl:using | initials=MD | title=System Logging | desc=The page describes how to system log. | project=OE 5.0 }}
-EMAC OE Linux 5.0 uses Busybox's syslog daemon, <code>syslogd</code>, by default.  However, the <code>syslog-ng</code> package can be installed to provide a much more capable system logging daemon, when needed.
+EMAC OE Linux 5.X uses Busybox's syslog daemon, <code>syslogd</code>, by default.  However, the <code>syslog-ng</code> package can be installed to provide a much more capable system logging daemon, when needed.
 ===Default Syslog Daemon===

@@ Line 398: / Line 398: @@
 {{clio |logger "Default settings message example"}}
 {{clio |tail -n 1 /var/log/messages}}
-Nov 17 19:20:23 ipac9x25 user.notice root: Default settings message example{{clos}}
+Nov 17 19:20:23 ipac9x25 user.notice root: Default settings message example
 To send a message to the system log with severity 3 (err):

@@ Line 1: / Line 1: @@
-{{todo| FinalDraft (04.13.2015-14:44->BS+)(11.10.2015-18:00->MD+)(11.11.2015-10:30->MD+)(11.17.2015-18:10->MD+);(11.18.2015-12:55->MD+)(11.18.2015-14:50->MD+)(11.18.2015-15:10->KY+)|Mike Dean| project=OE 5.0,MD,FinalDraft }}
+{{todo| Complete (04.13.2015-14:44->BS+)(11.10.2015-18:00->MD+)(11.11.2015-10:30->MD+)(11.17.2015-18:10->MD+);(11.18.2015-12:55->MD+)(11.18.2015-14:50->MD+)(11.18.2015-15:10->KY+);(11.18.2015-15:50->ER+)|Mike Dean| project=OE 5.0,MD,Complete}}
 {{#seo:
 |title=System Logging

@@ Line 1: / Line 1: @@
-{{todo| Review (04.13.2015-14:44->BS+)(11.10.2015-18:00->MD+)(11.11.2015-10:30->MD+)(11.17.2015-18:10->MD+);(11.18.2015-12:55->MD+)(11.18.2015-14:50->MD+)|Mike Dean| project=OE 5.0,MD,Review }}
+{{todo| FinalDraft (04.13.2015-14:44->BS+)(11.10.2015-18:00->MD+)(11.11.2015-10:30->MD+)(11.17.2015-18:10->MD+);(11.18.2015-12:55->MD+)(11.18.2015-14:50->MD+)(11.18.2015-15:10->KY+)|Mike Dean| project=OE 5.0,MD,FinalDraft }}
 {{#seo:
 |title=System Logging
@@ Line 24: / Line 24: @@
 ==== Facilities ====
-In syslog terminology, a facility is a category for log messages.  There are generally at least seven standard syslog facilities on any Linux syslog system.  The following list shows the standard seven as well as some which are rarely used anymore (especially in embedded systems).  The name of the facility is followed, in parenthesis, by the integer facility code associated with the facility, which is then followed by a description of the facility.  The ones you should not expect to find on an embedded system are demarcated with an asterisk (*):
+In syslog terminology, a facility is a category for log messages.  There are generally at least seven standard syslog facilities on any Linux syslog system.  The following list shows the standard seven, as well as some which are rarely used anymore (especially in embedded systems).  The name of the facility is followed, in parenthesis, by the integer facility code associated with the facility, which is then followed by a description of the facility.  The ones you should not expect to find on an embedded system are demarcated with an asterisk (*):
 ;kern(0)

@@ Line 1: / Line 1: @@
-{{todo| Review (04.13.2015-14:44->BS+)(11.10.2015-18:00->MD+)(11.11.2015-10:30->MD+)(11.17.2015-18:10->MD+);(11.18.2015-12:55->MD+)|Mike Dean| project=OE 5.0,MD,Review }}
+{{todo| Review (04.13.2015-14:44->BS+)(11.10.2015-18:00->MD+)(11.11.2015-10:30->MD+)(11.17.2015-18:10->MD+);(11.18.2015-12:55->MD+)(11.18.2015-14:50->MD+)|Mike Dean| project=OE 5.0,MD,Review }}
 {{#seo:
 |title=System Logging
@@ Line 494: / Line 494: @@
 <br /><br />
 This function takes no arguments.
 }}

@@ Line 1: / Line 1: @@
-{{todo| InProgress (04.13.2015-14:44->BS+)(11.10.2015-18:00->MD+)(11.11.2015-10:30->MD+)|Mike Dean| project=OE 5.0,BS,MD }}
+{{todo| InProgress (04.13.2015-14:44->BS+)(11.10.2015-18:00->MD+)(11.11.2015-10:30->MD+)(11.17.2015-18:10->MD+)|Mike Dean| project=OE 5.0,BS,MD }}
 {{#seo:
 |title=System Logging
@@ Line 312: / Line 312: @@
 The relevant functions are:
-<br /><br />
-{{ note |<code>'''void openlog( const char * ident, int option, int facility )'''</code>
+{{function | name=openlog |
-: <br />The <code>openlog()</code> function is used to (optionally) open a connection to the log daemon before writing log messages.  If the <code>openlog()</code> function is called, the <code>closelog()</code> function must also be called before exiting.  <br /><br />The following parameters are accepted by this function:<br /><br />
+<code>'''void openlog( const char * ident, int option, int facility )'''</code>
-:;<code>''ident''</code>
+<br /><br />The <code>openlog()</code> function is used to (optionally) open a connection to the log daemon before writing log messages.  If the <code>openlog()</code> function is called, the <code>closelog()</code> function must also be called before exiting.  <br /><br />The following parameters are accepted by this function:<br /><br />
 :: The <code>ident</code> parameter is an identification string to use for log messages.  This is just like the tag option to the <code>logger</code> command available from the shell.  If this parameter is <code>null</code>, the identification string defaults to the name of the process sending the messages.
-:;<code>''option''</code>
+:;<code>'''option'''</code>
 :: The <code>option</code> parameter is a bit string which accepts the following single bit masks:
 ::;<code>'''LOG_PERROR'''</code>
 ::: If on, any log messages sent will also go to the <code>stderr</code> stream associated with the current process.
-::;<code>''LOG_CONS''</code>
+::;<code>'''LOG_CONS'''</code>
 ::: This useful flag causes any messages which were unable to be sent to the system logger (due to any kind of failure) will be sent to the system console instead.
-::;<code>''LOG_PID''</code>
+::;<code>'''LOG_PID'''</code>
 ::: When on, the process ID of the current process will be printed with each log message.  This is especially useful for programs which call <code>fork()</code> at some point in their lifetime.
-::;<code>''LOG_NDELAY''</code>
+::;<code>'''LOG_NDELAY'''</code>
 ::: This option forces the connection to be established immediately, rather than deferred to a later point (such as at the beginning of the first call to the <code>syslog()</code> function.)
-:;<code>''facility''</code>
+:;<code>'''facility'''</code>
 :: This is the facility to which the log messages should be directed.  The available facilities were described earlier in this document; see [[System_Logging#Facilities | facilities]].
 }}
 <!-- /*********************************************************************************************************/ -->

@@ Line 246: / Line 246: @@
 ===Writing to Syslog from Programs and Scripts===
-As mentioned previously, many languages support writing to the Linux system logging utility.  There are many handy libraries and functions for this.  Some of the most commonly used ones are shown here.
+As mentioned previously, many languages support writing to the Linux system logging daemon.  There are many handy libraries and functions which provide this capability.  Some of the most commonly used ones are shown here.
 ====Shell Utility: <code>logger</code>====
-Whether you are writing a shell script, or simply wish to enter something into the system logs from the commandline, the <code>logger</code> utility will give you the capability you need.  This simple command takes a few options, but it can also be run with the only argument being the message to log.
+Whether you are writing a shell script, or simply wishing to enter something into the system logs from the commandline, the <code>logger</code> utility will give you the capability you need.  This simple command takes a few options, but it can also be run with the only argument being the message to log.
 =====Arguments to <code>logger</code>=====
@@ Line 255: / Line 255: @@
 The following options are available for <code>logger</code>:
 ;<code>-t</code> ''TAG''
-: Takes a ''TAG'' as an argument.  This option specifies a tag to label the message with, which is useful for sorting through logs later.
+: Takes a ''TAG'' as an argument.  This option specifies a tag to use for labeling the message.  Tags are useful for sorting through logs later on.
 ;<code>-p</code> ''Priority''
 : Takes a ''Priority'' as an argument.  The priority may be specified as just a numeric priority level, identifying the severity of the message, or it can be specified as a tuple containing a facility name and a priority level, delimited by a dot (<code>.</code>).  If no facility is specified, the facility defaults to, <code>user</code>.  The severity levels are specified in [[System_Logging#Severity | severity]] above.  The facility names are specified in [[System_Logging#Facilities | facilities]] above.
@@ Line 306: / Line 306: @@
 ====Writing to Syslog from a C Program====
-There is a standard C function call on Linux for writing to the system logger.
+There is a standard C function call on Linux for writing to the system logger.  This function, <code>syslog()</code>, uses a persistent connection to the log facility which can be opened and closed using the associated <code>openlog()</code> and <code>closelog()</code> functions.  However, if the <code>syslog()</code> function is called without first calling <code>openlog()</code>, the <code>syslog()</code> function will open the connection implicitly.