Red Hat ENTERPRISE LINUX 5 - DEPLOYMENT Deployment Manual page 360

Chapter 22. Apache HTTP Server
BrowserMatch
The BrowserMatch directive allows the server to define environment variables and take appropriate
actions based on the User-Agent HTTP header field — which identifies the client's Web browser type.
By default, the Web server uses BrowserMatch to deny connections to specific browsers with known
problems and also to disable keepalives and HTTP header flushes for browsers that are known to
have problems with those actions.
Cache Directives
A number of commented cache directives are supplied by the default Apache HTTP Server
configuration file. In most cases, uncommenting these lines by removing the hash mark (#) from
the beginning of the line is sufficient. The following, however, is a list of some of the more important
cache-related directives.
• CacheEnable — Specifies whether the cache is a disk, memory, or file descriptor cache. By default
CacheEnable configures a disk cache for URLs at or below /.
• CacheRoot — Specifies the name of the directory containing cached files. The default CacheRoot
is the /var/httpd/proxy/ directory.
• CacheSize — Specifies how much space the cache can use in kilobytes. The default CacheSize
is 5 KB.
The following is a list of some of the other common cache-related directives.
• CacheMaxExpire — Specifies how long HTML documents are retained (without a reload from the
originating Web server) in the cache. The default is 24 hours (86400 seconds).
• CacheLastModifiedFactor — Specifies the creation of an expiry (expiration) date for a
document which did not come from its originating server with its own expiry set. The default
CacheLastModifiedFactor is set to 0.1, meaning that the expiry date for such documents
equals one-tenth of the amount of time since the document was last modified.
• CacheDefaultExpire — Specifies the expiry time in hours for a document that was received
using a protocol that does not support expiry times. The default is set to 1 hour (3600 seconds).
• NoProxy — Specifies a space-separated list of subnets, IP addresses, domains, or hosts whose
content is not cached. This setting is most useful for Intranet sites.
CacheNegotiatedDocs
By default, the Web server asks proxy servers not to cache any documents which were negotiated on
the basis of content (that is, they may change over time or because of the input from the requester). If
CacheNegotiatedDocs is set to on, this function is disabled and proxy servers are allowed to cache
such documents.
CustomLog
CustomLog identifies the log file and the log file format. By default, the access log is recorded to the /
var/log/httpd/access_log file while errors are recorded in the /var/log/httpd/error_log
file.
The default CustomLog format is the combined log file format, as illustrated here:
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