overwrite that file with arbitrary data. If the log files themselves are writeable (by a non-root user), then someone may be able to overwrite the log itself with bogus data. 13http://httpd.apache.org/lists A filter is a process that is applied to data that is sent or received by the server. Data sent by clients to the server is processed by input filters while data sent by the server to the client is processed processed by output filters. Multiple filters can be applied to the data, and the order of the filters can be explicitly specified. Filters are used internally by Apache to perform functions such as chunking

likely degrade performance. Operating System Caching Almost all modern operating systems cache file-data in memory managed directly by the kernel. This is a powerful feature, and for the most part operating header" file, which includes meta- information about the URL, such as when it is due to expire and a ".data" file which is a verbatim copy of the content to be served. In the case of a content negotiated via a ".vary" directory will be created for the URL in question. This directory will have multiple ".data" files corresponding to the differently negotiated content. Maintaining the Disk Cache Although

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 537 10.35 Apache Module mod data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 540 10.36 Apache Module loaded, it will now set some default timeouts. • MOD DUMPIO: DUMPIOLOGLEVEL is no longer supported. Data is always logged at LOGLEVEL trace7. 1.1. UPGRADING TO 2.4 FROM 2.2 5 • On Unix platforms, piped now skip compression if it knows that the size overhead added by the compression is larger than the data to be compressed. • Multi-language error documents from 2.2.x may not work unless they are adjusted

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 537 10.35 Apache Module mod data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 540 10.36 Apache Module loaded, it will now set some default timeouts. • MOD DUMPIO: DUMPIOLOGLEVEL is no longer supported. Data is always logged at LOGLEVEL trace7. 1.1. UPGRADING TO 2.4 FROM 2.2 5 • On Unix platforms, piped now skip compression if it knows that the size overhead added by the compression is larger than the data to be compressed. • Multi-language error documents from 2.2.x may not work unless they are adjusted

likely degrade performance. Operating System Caching Almost all modern operating systems cache file-data in memory managed directly by the kernel. This is a powerful feature, and for the most part operating header" file, which includes meta-information about the URL, such as when it is due to expire and a ".data" file which is a verbatim copy of the content to be served. In the case of a content negotiated via a ".vary" directory will be created for the URL in question. This directory will have multiple ".data" files corresponding to the differently negotiated content. Maintaining the Disk Cache Although

likely degrade performance. Operating System Caching Almost all modern operating systems cache file-data in memory managed directly by the kernel. This is a powerful feature, and for the most part operating header" file, which includes meta-information about the URL, such as when it is due to expire and a ".data" file which is a verbatim copy of the content to be served. In the case of a content negotiated via a ".vary" directory will be created for the URL in question. This directory will have multiple ".data" files corresponding to the differently negotiated content. Maintaining the Disk Cache Although

likely degrade performance. Operating System Caching Almost all modern operating systems cache file-data in memory managed directly by the kernel. This is a powerful feature, and for the most part operating header" file, which includes meta-information about the URL, such as when it is due to expire and a ".data" file which is a verbatim copy of the content to be served. In the case of a content negotiated via a ".vary" directory will be created for the URL in question. This directory will have multiple ".data" files corresponding to the differently negotiated content. Maintaining the Disk Cache Although

likely degrade performance. Operating System Caching Almost all modern operating systems cache file-data in memory managed directly by the kernel. This is a powerful feature, and for the most part operating header" file, which includes meta-information about the URL, such as when it is due to expire and a ".data" file which is a verbatim copy of the content to be served. In the case of a content negotiated via a ".vary" directory will be created for the URL in question. This directory will have multiple ".data" files corresponding to the differently negotiated content. Maintaining the Disk Cache Although

. . . . . . . . . . . . . . . . . . . . . . . . . . . 582 CONTENTS vii 10.37 Apache Module mod data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 585 10.38 Apache Module loaded, it will now set some default timeouts. • MOD DUMPIO: DUMPIOLOGLEVEL is no longer supported. Data is always logged at LOGLEVEL trace7. • On Unix platforms, piped logging commands configured using now skip compression if it knows that the size overhead added by the compression is larger than the data to be compressed. • Multi-language error documents from 2.2.x may not work unless they are adjusted

. . . . . . . . . . . . . . . . . . . . . . . . . . . 582 CONTENTS vii 10.37 Apache Module mod data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 585 10.38 Apache Module loaded, it will now set some default timeouts. • MOD DUMPIO: DUMPIOLOGLEVEL is no longer supported. Data is always logged at LOGLEVEL trace7. • On Unix platforms, piped logging commands configured using now skip compression if it knows that the size overhead added by the compression is larger than the data to be compressed. • Multi-language error documents from 2.2.x may not work unless they are adjusted