boa - a single-tasking high performance http server
boa [-c server_root] [-r chroot] [-d]
Boa is a single-tasking HTTP server. That means that unlike traditional
web servers, it does not fork for each incoming connection, nor does it
fork many copies of itself to handle multiple connections. It
internally multiplexes all of the ongoing HTTP connections, and forks
only for CGI programs (which must be separate processes.) Preliminary
tests show Boa is more than twice as fast as Apache.
The primary design goals of Boa are speed and security. Security, in
the sense of "can’t be subverted by a malicious user", not "fine
grained access control and encrypted communications". Boa is not
intended as a feature-packed server; if you want one of those, check
out WN from John Franks. Modifications to Boa that improve its speed,
security, robustness, and portability, are eagerly sought. Other
features may be added if they can be achieved without hurting the
-d instruct Boa not to fork itself (non-daemonize).
choose a server root overriding the default SERVER_ROOT #define
The server root must hold your local copy of the configuration
instruct Boa where to chdir and chroot to. The chdir/chroot is
done before the configuration file is read, or any log files are
boa.conf - the sole configuration file for Boa.
The directives in this file are defined in the DIRECTIVES
mime.types - the
MimeTypes <filename> defines what Content-Type Boa will send in
an HTTP/1.0 or better transaction.
The Boa configuration file is parsed with a lex/yacc or flex/bison
generated parser. If it reports an error, the line number will be
provided; it should be easy to spot. The syntax of each of these rules
is very simple, and they can occur in any order. Where possible, these
directives mimic those of NCSA httpd 1.3; We saw no reason to introduce
Note: the "ServerRoot" is not in this configuration file. It can be
compiled into the server (see defines.h ) or specified on the command
line with the -c option.
The following directives are contained in the boa.conf file, and most,
but not all, are required.
This is the port that Boa runs on. The default port for http
servers is 80. If it is less than 1024, the server must be
started as root.
User <user name or UID>
The name or UID the server should run as. For Boa to attempt
this, the server must be started as root.
Group <group name or GID>
The group name or GID the server should run as. For Boa to
attempt this, the server must be started as root.
ServerAdmin <email address>
The email address where server problems should be sent. Note:
this is not currently used.
Where to put the pid of the process. Comment out to write no
pid file. Note: Because Boa drops privileges at startup, and
the pid file is written by the UID/GID before doing so, Boa does
not attempt removal of the pid file.
The location of the error log file. If this does not start with
/, it is considered relative to the server root. Set to
/dev/null if you don’t want errors logged.
The location of the access log file. If this does not start
with /, it is considered relative to the server root. Comment
out or set to /dev/null (less effective) to disable access
This is a logical switch and does not take any parameters.
Comment out to disable.
The location of the CGI error log file. If this does not start
with /, it is considered relative to the server root. If
specified, this is the file that the stderr of CGIs is tied to,
*instead* of to the ErrorLog.
The CGIumask is set immediately before execution of the CGI.
The default value is 027. The number must be interpretable
unambiguously by the C function strtol. No base is specified, so
one may use a hexadecimal, decimal, or octal number if it is
The name of this server that should be sent back to clients if
different than that returned by gethostname.
This is a logical switch and does not take any parameters.
Comment out to disable. Given DocumentRoot /var/www, requests
on interface ’A’ or IP ’IP-A’ become /var/www/IP-A. Example:
http://localhost/ becomes /var/www/127.0.0.1
The root location for all virtually hosted data Comment out to
disable. Incompatible with ’Virtualhost’ and ’DocumentRoot’!!
Given VHostRoot /var/www, requests to host foo.bar.com, where
foo.bar.com is ip a.b.c.d, become /var/www/a.b.c.d/foo.bar.com
Hostnames are "cleaned", and must conform to the rules specified
in rfc1034, which are be summarized here:
Hostnames must start with a letter, end with a letter or digit,
and have as interior characters only letters, digits, and
hyphen. Hostnames must not exceed 63 characters in length.
Define this in order to have a default hostname when the client
does not specify one, if using VirtualHostName. If not
specified, the word "default" will be used for compatibility
with older clients.
The root directory of the HTML documents. If this does not start
with /, it is considered relative to the server root.
The name of the directory which is appended onto a user’s home
directory if a ~user request is received.
Name of the file to use as a pre-written HTML directory index.
Please make and use these files. On the fly creation of
directory indexes can be slow.
Name of the program used to generate on-the-fly directory
listings. The program must take one or two command-line
arguments, the first being the directory to index (absolute),
and the second, which is optional, contains what Boa would have
the "title" of the document be. Comment out if you don’t want
on the fly directory listings. If this does not start with /,
it is considered relative to the server root.
Number of KeepAlive requests to allow per connection. Comment
out, or set to 0 to disable keepalive processing.
Number of seconds to wait before keepalive connections time out.
The location of the mime.types file. If this does not start
with /, it is considered relative to the server root. Set to
/dev/null if you do not want to load a mime types file. Do *not*
comment out (better use AddType!)
DefaultType <mime type>
MIME type used if the file extension is unknown, or there is no
AddType <mime type> <extension> [extension...]
Associates a MIME type with an extension or extensions.
Redirect, Alias, and ScriptAlias <path1> <path2>
Redirect, Alias, and ScriptAlias all have the same semantics --
they match the beginning of a request and take appropriate
action. Use Redirect for other servers, Alias for the same
server, and ScriptAlias to enable directories for script
Redirect allows you to tell clients about documents which used
to exist in your server’s namespace, but do not anymore. This
allows you tell the clients where to look for the relocated
Alias aliases one path to another. Of course, symbolic links in
the file system work fine too.
ScriptAlias maps a virtual path to a directory for serving
Please see the included boa.conf for defaults and examples.
Like the Linux kernel, even numbered versions are "stable", and odd
numbered versions are "unstable", or rather, "development". Versions
0.91 and 0.91beta of Boa were released by Paul Phillips
Version 0.92 was released by Larry Doolittle on December 12, 1996.
Version 0.93 was the development version of 0.94.
Version 0.94 was released 22 Jan 2000.
There are probably bugs, but we are not aware of any at this time.
Boa was created by Paul Phillips <firstname.lastname@example.org>. It is now being
maintained and enhanced by Larry Doolittle <email@example.com> and Jon
Linux is the development platform at the moment, other OS’s are known
to work. If you’d like to contribute to this effort, contact Larry or
Jon via e-mail.
This program is distributed under the GNU General Public License, as
noted in each source file.