When dealing with daemons managed by Upstart, logging output becomes crucial for debugging and monitoring. The behavior differs between Ubuntu versions, particularly when moving from 0.3.9 (Hardy) to 0.6.x (Lucid).

In Upstart 0.3.9, you could use the console logged stanza to capture output:

description "My Daemon Service"
author "Your Name"

start on runlevel [2345]
stop on runlevel [016]

console logged
exec /path/to/your/daemon

This would automatically log to /var/log/upstart/your-daemon.log. However, this method was deprecated in later versions.

For newer Upstart versions, consider these approaches:

Method 1: Direct Output to syslog

description "Modern Daemon Service"
author "Your Name"

start on runlevel [2345]
stop on runlevel [016]

exec /path/to/daemon 2>&1 | logger -t mydaemon

This pipes both stdout and stderr to syslog, viewable in /var/log/syslog.

Method 2: Custom Log File

description "Custom Log Daemon"
author "Your Name"

start on runlevel [2345]
stop on runlevel [016]

script
    exec /path/to/daemon >> /var/log/mydaemon.log 2>&1
end script

The transition period requires special handling. If you need compatibility across versions:

description "Cross-version Daemon"
author "Your Name"

start on runlevel [2345]
stop on runlevel [016]

script
    # For 0.3.9
    if [ -e /etc/init.d/.upstart-version ] && 
       [ "$(cat /etc/init.d/.upstart-version)" = "0.3.9" ]; then
        exec /path/to/daemon
    else
        # For 0.6.x
        exec /path/to/daemon >> /var/log/mydaemon.log 2>&1
    fi
end script

Remember to configure log rotation in /etc/logrotate.d/:

/var/log/mydaemon.log {
    weekly
    missingok
    rotate 4
    compress
    delaycompress
    notifempty
    create 640 root adm
}

For systems migrating to systemd, the logging approach changes completely:

[Unit]
Description=My Daemon Service

[Service]
ExecStart=/path/to/daemon
StandardOutput=syslog
StandardError=syslog
SyslogIdentifier=mydaemon

[Install]
WantedBy=multi-user.target

When managing daemons with Upstart on Ubuntu servers, one common pain point is capturing the application's stdout/stderr output. The behavior varies significantly between Upstart versions, particularly when moving from Hardy (0.3.9) to Lucid (0.6.x) and later.

In Ubuntu Hardy (0.3.9), the console logged stanza directs output to the system log file:

# Example Upstart job for 0.3.9
description "My Daemon Service"
author "Your Name"

start on runlevel [2345]
stop on runlevel [016]

console logged
exec /usr/local/bin/mydaemon --verbose

This logs to /var/log/daemon.log by default. You can verify with:

grep 'My Daemon' /var/log/daemon.log

For Ubuntu Lucid (0.6.5) and later, console logged was deprecated. Instead, use these approaches:

Method 1: Direct to syslog

description "Modern Daemon"
author "Your Name"

start on runlevel [2345]
stop on runlevel [016]

# Log to syslog with custom facility
console none
exec /usr/local/bin/mydaemon 2>&1 | logger -t mydaemon

Method 2: Custom Log File

description "File-Logged Daemon"
author "Your Name"

start on runlevel [2345]
stop on runlevel [016]

console none
script
    exec /usr/local/bin/mydaemon >> /var/log/mydaemon.log 2>&1
end script

For production systems, create a logrotate config at /etc/logrotate.d/mydaemon:

/var/log/mydaemon.log {
    weekly
    missingok
    rotate 12
    compress
    delaycompress
    notifempty
    create 640 root adm
    sharedscripts
    postrotate
        /usr/bin/killall -HUP mydaemon || true
    endscript
}

When troubleshooting:

• Check initctl log-priority to verify logging level
• Use initctl emit --no-wait mydaemon for manual triggering
• Monitor with tail -f /var/log/syslog | grep mydaemon