unicorn - a rackup-like command to launch the Unicorn HTTP
unicorn [-c CONFIG_FILE] [-E RACK_ENV] [-D] [RACKUP_FILE]
A rackup(1)-like command to launch Rack applications using
Unicorn. It is expected to be started in your application root
(APP_ROOT), but the "working_directory" directive may be used
in the CONFIG_FILE.
While unicorn takes a myriad of command-line options for
compatibility with ruby(1) and rackup(1), it is recommended to
stick to the few command-line options specified in the SYNOPSIS
and use the CONFIG_FILE as much as possible.
This defaults to "config.ru" in APP_ROOT. It should be the
same file used by rackup(1) and other Rack launchers, it uses
the Rack::Builder DSL.
Embedded command-line options are mostly parsed for
compatibility with rackup(1) but strongly discouraged.
-c, --config-file CONFIG_FILE
Path to the Unicorn-specific config file. The config
file is implemented as a Ruby DSL, so Ruby code may
executed. See the RDoc/ri for the Unicorn::Configurator
class for the full list of directives available from the
DSL. Using an absolute path for for CONFIG_FILE is
recommended as it makes multiple instances of Unicorn
easily distinguishable when viewing ps(1) output.
Run daemonized in the background. The process is
detached from the controlling terminal and stdin is
redirected to "/dev/null". Unlike many common UNIX
daemons, we do not chdir to "/" upon daemonization to
allow more control over the startup/upgrade process.
Unless specified in the CONFIG_FILE, stderr and stdout
will also be redirected to "/dev/null".
-E, --env RACK_ENV
Run under the given RACK_ENV. See the RACK ENVIRONMENT
section for more details.
-l, --listen ADDRESS
Listens on a given ADDRESS. ADDRESS may be in the form
of HOST:PORT or PATH, HOST:PORT is taken to mean a TCP
socket and PATH is meant to be a path to a UNIX domain
socket. Defaults to "0.0.0.0:8080" (all addresses on
TCP port 8080) For production deployments, specifying
the "listen" directive in CONFIG_FILE is recommended as
it allows fine-tuning of socket options.
Disables loading middleware implied by RACK_ENV. This
bypasses the configuration documented in the RACK
ENVIRONMENT section, but still allows RACK_ENV to be
used for application/framework-specific purposes.
RACKUP COMPATIBILITY OPTIONS
-o, --host HOST
Listen on a TCP socket belonging to HOST, default is
"0.0.0.0" (all addresses). If specified multiple times
on the command-line, only the last-specified value takes
effect. This option only exists for compatibility with
the rackup(1) command, use of "-l"/"--listen" switch is
-p, --port PORT
Listen on the specified TCP PORT, default is 8080. If
specified multiple times on the command-line, only the
last-specified value takes effect. This option only
exists for compatibility with the rackup(1) command, use
of "-l"/"--listen" switch is recommended instead.
-s, --server SERVER
No-op, this exists only for compatibility with
-e, --eval LINE
Evaluate a LINE of Ruby code. This evaluation happens
immediately as the command-line is being parsed.
Turn on debug mode, the $DEBUG variable is set to true.
Turn on verbose warnings, the $VERBOSE variable is set
-I, --include PATH
specify $LOAD_PATH. PATH will be prepended to
$LOAD_PATH. The ':' character may be used to delimit
multiple directories. This directive may be used more
than once. Modifications to $LOAD_PATH take place
immediately and in the order they were specified on the
-r, --require LIBRARY
require a specified LIBRARY before executing the
application. The "require" statement will be executed
immediately and in the order they were specified on the
The following UNIX signals may be sent to the master process:
• HUP - reload config file, app, and gracefully restart all
• INT/TERM - quick shutdown, kills all workers immediately
• QUIT - graceful shutdown, waits for workers to finish their
current request before finishing.
• USR1 - reopen all logs owned by the master and all workers
See Unicorn::Util.reopen_logs for what is considered a log.
• USR2 - reexecute the running binary. A separate QUIT should
be sent to the original process once the child is verified to
be up and running.
• WINCH - gracefully stops workers but keep the master running.
This will only work for daemonized processes.
• TTIN - increment the number of worker processes by one
• TTOU - decrement the number of worker processes by one
See the SIGNALS (https://yhbt.net/unicorn/SIGNALS.html)
document for full description of all signals used by Unicorn.
Accepted values of RACK_ENV and the middleware they
automatically load (outside of RACKUP_FILE) are exactly as
those in rackup(1):
• development - loads Rack::CommonLogger, Rack::ShowExceptions,
• deployment - loads Rack::CommonLogger middleware
• none - loads no middleware at all, relying entirely on
All unrecognized values for RACK_ENV are assumed to be "none".
Production deployments are strongly encouraged to use
"deployment" or "none" for maximum performance.
As of Unicorn 0.94.0, RACK_ENV is exported as a process-wide
environment variable as well. While not current a part of the
Rack specification as of Rack 1.0.1, this has become a de facto
standard in the Rack world.
Note the Rack::ContentLength and Rack::Chunked middlewares are
also loaded by "deployment" and "development", but no other
values of RACK_ENV. If needed, they must be individually
specified in the RACKUP_FILE, some frameworks do not require
The RACK_ENV variable is set by the aforementioned -E switch.
All application or library-specific environment variables (e.g.
TMPDIR) may always be set in the Unicorn CONFIG_FILE in
addition to the spawning shell. When transparently upgrading
Unicorn, all environment variables set in the old master
process are inherited by the new master process. Unicorn only
uses (and will overwrite) the UNICORN_FD environment variable
internally when doing transparent upgrades.
UNICORN_FD is a comma-delimited list of one or more file
descriptors used to implement USR2 upgrades. Init systems may
bind listen sockets itself and spawn unicorn with UNICORN_FD
set to the file descriptor numbers of the listen socket(s).
As of unicorn 5.0, LISTEN_PID and LISTEN_FDS are used for
socket activation as documented in the sd_listen_fds(3)
manpage. Users relying on this feature do not need to specify
a listen socket in the unicorn config file.
• Rack::Builder ri/RDoc
• Unicorn::Configurator ri/RDoc
• unicorn RDoc ⟨https://yhbt.net/unicorn/⟩
• Rack RDoc ⟨https://www.rubydoc.info/github/rack/rack/⟩
• Rackup HowTo
The Unicorn Community <firstname.lastname@example.org>.
Unicorn User Manual September 15, 2009 UNICORN(1)
mail archives: https://yhbt.net/unicorn-public/
source code: git clone https://yhbt.net/unicorn.git
torsocks git clone http://ou63pmih66umazou.onion/unicorn.git