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153 lines
3.8 KiB
Groff
153 lines
3.8 KiB
Groff
'\" t
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.TH "NSS\-MYHOSTNAME" "8" "" "systemd 219" "nss-myhostname"
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.\" -----------------------------------------------------------------
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.\" * Define some portability stuff
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.\" -----------------------------------------------------------------
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.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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.\" http://bugs.debian.org/507673
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.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
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.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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.ie \n(.g .ds Aq \(aq
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.el .ds Aq '
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.\" -----------------------------------------------------------------
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.\" * set default formatting
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.\" -----------------------------------------------------------------
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.\" disable hyphenation
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.nh
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.\" disable justification (adjust text to left margin only)
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.ad l
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.\" -----------------------------------------------------------------
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.\" * MAIN CONTENT STARTS HERE *
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.\" -----------------------------------------------------------------
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.SH "NAME"
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nss-myhostname, libnss_myhostname.so.2 \- Provide hostname resolution for the locally configured system hostname\&.
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.SH "SYNOPSIS"
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.PP
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libnss_myhostname\&.so\&.2
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.SH "DESCRIPTION"
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.PP
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\fBnss\-myhostname\fR
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is a plugin for the GNU Name Service Switch (NSS) functionality of the GNU C Library (\fBglibc\fR) primarily providing hostname resolution for the locally configured system hostname as returned by
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\fBgethostname\fR(2)\&. The precise hostnames resolved by this module are:
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.sp
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.RS 4
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.ie n \{\
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\h'-04'\(bu\h'+03'\c
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.\}
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.el \{\
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.sp -1
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.IP \(bu 2.3
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.\}
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The local, configured hostname is resolved to all locally configured IP addresses ordered by their scope, or \(em if none are configured \(em the IPv4 address 127\&.0\&.0\&.2 (which is on the local loopback) and the IPv6 address ::1 (which is the local host)\&.
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.RE
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.sp
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.RS 4
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.ie n \{\
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\h'-04'\(bu\h'+03'\c
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.\}
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.el \{\
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.sp -1
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.IP \(bu 2.3
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.\}
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The hostname
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"localhost"
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is resolved to the IP addresses 127\&.0\&.0\&.1 and ::1\&.
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.RE
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.sp
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.RS 4
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.ie n \{\
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\h'-04'\(bu\h'+03'\c
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.\}
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.el \{\
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.sp -1
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.IP \(bu 2.3
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.\}
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The hostname
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"gateway"
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is resolved to all current default routing gateway addresses, ordered by their metric\&. This assigns a stable hostname to the current gateway, useful for referencing it independently of the current network configuration state\&.
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.RE
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.PP
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Various software relies on an always\-resolvable local hostname\&. When using dynamic hostnames, this is traditionally achieved by patching
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/etc/hosts
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at the same time as changing the hostname\&. This is problematic since it requires a writable
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/etc
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file system and is fragile because the file might be edited by the administrator at the same time\&. With
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\fBnss\-myhostname\fR
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enabled changing
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/etc/hosts
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is unncessary, and on many systems the file becomes entirely optional\&.
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.PP
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To activate the NSS modules,
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"myhostname"
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has to be added to the line starting with
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"hosts:"
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in
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/etc/nsswitch\&.conf\&.
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.PP
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It is recommended to place
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"myhostname"
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last in the
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nsswitch\&.conf
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line to make sure that this mapping is only used as fallback, and any DNS or
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/etc/hosts
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based mapping takes precedence\&.
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.SH "EXAMPLE"
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.PP
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Here\*(Aqs an example
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/etc/nsswitch\&.conf
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file, that enables
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\fBmyhostname\fR
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correctly:
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.sp
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.if n \{\
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.RS 4
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.\}
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.nf
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passwd: compat
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group: compat
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shadow: compat
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hosts: files dns mymachines \fBmyhostname\fR
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networks: files
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protocols: db files
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services: db files
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ethers: db files
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rpc: db files
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netgroup: nis
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.fi
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.if n \{\
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.RE
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.\}
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.PP
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To test, use
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\fBglibc\fR\*(Aqs
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\fBgetent\fR
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tool:
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.sp
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.if n \{\
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.RS 4
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.\}
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.nf
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$ getent ahosts `hostname`
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::1 STREAM omega
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::1 DGRAM
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::1 RAW
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127\&.0\&.0\&.2 STREAM
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127\&.0\&.0\&.2 DGRAM
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127\&.0\&.0\&.2 RAW
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.fi
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.if n \{\
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.RE
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.\}
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.PP
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In this case the local hostname is
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\fIomega\fR\&.
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.SH "SEE ALSO"
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.PP
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\fBsystemd\fR(1),
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\fBnss-mymachines\fR(8),
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\fBnsswitch.conf\fR(5),
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\fBgetent\fR(1)
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