NAME (名稱)

host.conf - 解析配置文件  

DESCRIPTION (描述)

文件 /etc/host.conf 包含了為解析庫聲明的配置信息. 它應該每行含一個配置關鍵字, 其后跟著合適的配置信息. 系統(tǒng)識別的關鍵字有: order, trim, multi, nospoof和 reorder. 每個關鍵字在下面將分別進行介紹:

order

這個關鍵字確定了主機查詢是如何執(zhí)行的. 它后面應該跟隨一個或者更多的查詢方式, 這些查詢方式用逗號分隔. 有效的方式有: bind, hosts和 nis.

trim

這個關鍵字可以多次出現(xiàn). 每次出現(xiàn)其后應該跟隨單個的以句點開頭的域名. 如果設置了它, resolv+ 庫會自動截去任何通過 DNS 解析出來的主機名后面的域名. 這個選項用于本地主機和域. (相關信息: trim 對于通過 NIS 或者 hosts 文件獲取的主機名無效. 需要注意的是要確保在 hosts 文件中的每條記錄的第一個主機名是全名或者非全名, 以適合于本地安裝.)

multi

有效的值為: on和 off. 如果設置為 on, resolv+ 庫會返回一臺主機在 /etc/hosts 文件中出現(xiàn)的的所有有效地址, 而不只是第一個. 默認情況下設為 off , 否則可能會導致?lián)碛旋嫶?hosts 文件的站點潛在的性能損失.

nospoof

有效的值為: on 和 off. 如果設置為 on, resolv+ 庫會嘗試阻止主機名欺騙以提高使用 rlogin 和 rsh 的安全性. 它是如下這樣工作的: 在執(zhí)行了一個主機地址的查詢之后, resolv+ 會對該地址執(zhí)行一次主機名的查詢. 如果兩者不匹配, 查詢即失敗.

spoofalert

如果該選項設為 on 同時也設置了 nospoof 選項, resolv+ 會通過 syslog 設施記錄錯誤報警信息. 默認的值為 off.

reorder

有效的值為 on 和 off. 如果設置為 on, resolv+ 會試圖重新排列主機地址, 以便執(zhí)行 gethostbyname(3) 時, 首先列出本地地址(即在同一子網(wǎng)中的地址). 重新排序適合于所有查詢方式. 默認的值為 off.

FILES(相關文件)

/etc/host.conf

解析配置文件

/etc/resolv.conf

解析配置文件

/etc/hosts

本地主機數(shù)據(jù)庫

SEE ALSO(又見)

gethostbyname(3), hostname(7), resolv+(8), named(8)

#p#

NAME

host.conf - resolver configuration file  

DESCRIPTION

The file /etc/host.conf contains configuration information specific to the resolver library. It should contain one configuration keyword per line, followed by appropriate configuration information. The keywords recognized are order, trim, multi, nospoof, spoof, and reorder. These keywords are described below.

order

This keyword specifies how host lookups are to be performed. It should be followed by one or more lookup methods, separated by commas. Valid methods are bind, hosts, and nis.

trim

This keyword may be listed more than once. Each time it should be followed by a list of domains, separated by colons (`:'), semicolons (`;') or commas (`,'), with the leading dot. When set, the resolv+ library will automatically trim the given domain name from the end of any hostname resolved via DNS. This is intended for use with local hosts and domains. (Related note: trim will not affect hostnames gathered via NIS or the hosts file. Care should be taken to ensure that the first hostname for each entry in the hosts file is fully qualified or non-qualified, as appropriate for the local installation.)

multi

Valid values are on and off. If set to on, the resolv+ library will return all valid addresses for a host that appears in the /etc/hosts file, instead of only the first. This is off by default, as it may cause a substantial performance loss at sites with large hosts files.

nospoof

Valid values are on and off. If set to on, the resolv+ library will attempt to prevent hostname spoofing to enhance the security of rlogin and rsh. It works as follows: after performing a host address lookup, resolv+ will perform a hostname lookup for that address. If the two hostnames do not match, the query will fail. The default value is off.

spoofalert

Valid values are on and off. If this option is set to on and the nospoof option is also set, resolv+ will log a warning of the error via the syslog facility. The default value is off.

spoof

Valid values are off, nowarn and warn. If this option is set to off, spoofed addresses are permitted and no warnings will be emitted via the syslog facility. If this option is set to warn, resolv+ will attempt to prevent hostname spoofing to enhance the security and log a warning of the error via the syslog facility. If this option is set to nowarn, the resolv+ library will attempt to prevent hostname spoofing to enhance the security but not emit warnings via the syslog facility. Setting this option to anything else is equal to setting it to nowarn.

reorder

Valid values are on and off. If set to on, resolv+ will attempt to reorder host addresses so that local addresses (i.e., on the same subnet) are listed first when a gethostbyname(3) is performed. Reordering is done for all lookup methods. The default value is off.

ENVIRONMENT

There are six environment variables that can be used to allow users to override the behavior which is configured in /etc/host.conf.

RESOLV_HOST_CONF

If set this variable points to a file that should be read instead of /etc/host.conf.

RESOLV_SERV_ORDER

Overrides the order command.

RESOLV_SPOOF_CHECK

Overrides the nospoof, spoofalert and spoof commands in the same way as the spoof command is parsed. Valid values are off, nowarn and warn.

RESOLV_MULTI

Overrides the multi command.

RESOLV_REORDER

Overrides the reorder command.

RESOLV_ADD_TRIM_DOMAINS

A list of domains, separated by colons (`:'), semicolons (`;') or commas (`,'), with the leading dot, which will be added to the list of domains that should be trimmed.

RESOLV_OVERRIDE_TRIM_DOMAINS

A list of domains, separated by colons (`:'), semicolons (`;') or commas (`,'), with the leading dot, which will replace the list of domains that should be trimmed. Overrides the trim command.

FILES

/etc/host.conf

Resolver configuration file

/etc/resolv.conf

Resolver configuration file

/etc/hosts

Local hosts database

NOTES

The following differences exist compared to the original implementation. A new command spoof and a new environment variable RESOLV_SPOOF_CHECK can take arguments like off, nowarn and warn. Line comments can appear anywhere and not only at the beginning of a line.  

SEE ALSO

gethostbyname(3), hostname(7), resolv+(8), named(8)