NAME (名称)
host.conf - 解析配置文件
DESCRIPTION (描述)
文件 /etc/host.conf 包含了为解析库声明的配置信息. 它应该每行含一个配置关键字, 其后跟着合适的配置信息. 系统识别的关键字有: order, trim, multi, nospoof和 reorder. 每个关键字在下面将分别进行介绍:
- order
- 这个关键字确定了主机查询是如何执行的. 它后面应该跟随一个或者更多的查询方式, 这些查询方式用逗号分隔. 有效的方式有: bind, hosts和 nis.
- trim
- 这个关键字可以多次出现. 每次出现其后应该跟随单个的以句点开头的域名. 如果设置了它, resolv+ 库会自动截去任何通过 DNS 解析出来的主机名后面的域名. 这个选项用于本地主机和域. (相关信息: trim 对于通过 NIS 或者 hosts 文件获取的主机名无效. 需要注意的是要确保在 hosts 文件中的每条记录的第一个主机名是全名或者非全名, 以适合于本地安装.)
- multi
- 有效的值为: on和 off. 如果设置为 on, resolv+ 库会返回一台主机在 /etc/hosts 文件中出现的的所有有效地址, 而不只是第一个. 默认情况下设为 off , 否则可能会导致拥有庞大 hosts 文件的站点潜在的性能损失.
- nospoof
- 有效的值为: on 和 off. 如果设置为 on, resolv+ 库会尝试阻止主机名欺骗以提高使用 rlogin 和 rsh 的安全性. 它是如下这样工作的: 在执行了一个主机地址的查询之后, resolv+ 会对该地址执行一次主机名的查询. 如果两者不匹配, 查询即失败.
- spoofalert
- 如果该选项设为 on 同时也设置了 nospoof 选项, resolv+ 会通过 syslog 设施记录错误报警信息. 默认的值为 off.
- reorder
- 有效的值为 on 和 off. 如果设置为 on, resolv+ 会试图重新排列主机地址, 以便执行 gethostbyname(3) 时, 首先列出本地地址(即在同一子网中的地址). 重新排序适合于所有查询方式. 默认的值为 off.
FILES(相关文件)
- /etc/host.conf
- 解析配置文件
- /etc/resolv.conf
- 解析配置文件
- /etc/hosts
- 本地主机数据库
SEE ALSO(又见)
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)
