unicorn - a rackup-like command to launch the Unicorn HTTP server
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.
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".
Run under the given RACK_ENV. See the RACK ENVIRONMENT section for more details.
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.
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 recommended instead.
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.
No-op, this exists only for compatibility with rackup(1).
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 to true.
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 command-line.
require a specified LIBRARY before executing the application. The "require" statement will be executed immediately and in the order they were specified on the command-line.
The following UNIX signals may be sent to the master process:
See the SIGNALS 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):
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 them.
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.
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