How to redirect output of systemd service to a file

Question

I think there's a more elegant way to solve the problem: send the stdout/stderr to syslog with an identifier and instruct your syslog manager to split its output by program name.

Use the following properties in your systemd service unit file:

StandardOutput=syslog
StandardError=syslog
SyslogIdentifier=<your program identifier> # without any quote

Then, assuming your distribution is using rsyslog to manage syslogs, create a file in /etc/rsyslog.d/<new_file>.conf with the following content:

if $programname == '<your program identifier>' then /path/to/log/file.log
& stop

Now make the log file writable by syslog:

# ls -alth /var/log/syslog 
-rw-r----- 1 syslog adm 439K Mar  5 19:35 /var/log/syslog
# chown syslog:adm /path/to/log/file.log

Restart rsyslog (sudo systemctl restart rsyslog) and enjoy! Your program stdout/stderr will still be available through journalctl (sudo journalctl -u <your program identifier>) but they will also be available in your file of choice.

Source via archive.org

If you have a newer distro with a newer systemd (systemd version 236 or newer), you can set the values of StandardOutput or StandardError to file:YOUR_ABSPATH_FILENAME.

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Long story:

In newer versions of systemd there is a relatively new option (the github request is from 2016 ish and the enhancement is merged/closed 2017 ish) where you can set the values of StandardOutput or StandardError to file:YOUR_ABSPATH_FILENAME. The file:path option is documented in the most recent systemd.exec man page.

This new feature is relatively new and so is not available for older distros like centos-7 (or any centos before that).

I would suggest adding stdout and stderr file in systemd service file itself.

Referring : https://www.freedesktop.org/software/systemd/man/systemd.exec.html#StandardOutput=

As you have configured it should not like:

StandardOutput=/home/user/log1.log
StandardError=/home/user/log2.log

It should be:

StandardOutput=file:/home/user/log1.log
StandardError=file:/home/user/log2.log

This works when you don't want to restart the service again and again.

This will create a new file and does not append to the existing file.

Use Instead:

StandardOutput=append:/home/user/log1.log
StandardError=append:/home/user/log2.log

NOTE: Make sure you create the directory already. I guess it does not support to create a directory.

You possibly get this error:

Failed to parse output specifier, ignoring: /var/log1.log

From the systemd.exec(5) man page:

StandardOutput=

Controls where file descriptor 1 (STDOUT) of the executed processes is connected to. Takes one of inherit, null, tty, journal, syslog, kmsg, journal+console, syslog+console, kmsg+console or socket.

The systemd.exec(5) man page explains other options related to logging. See also the systemd.service(5) and systemd.unit(5) man pages.

Or maybe you can try things like this (all on one line):

ExecStart=/bin/sh -c '/usr/local/bin/binary1 agent -config-dir /etc/sample.d/server 2>&1 > /var/log.log' 

If for a some reason can't use rsyslog, this will do: ExecStart=/bin/bash -ce "exec /usr/local/bin/binary1 agent -config-dir /etc/sample.d/server >> /var/log/agent.log 2>&1"