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Diffstat (limited to 'upstream/archlinux/man8/nss-myhostname.8')
| -rw-r--r-- | upstream/archlinux/man8/nss-myhostname.8 | 181 |
1 files changed, 181 insertions, 0 deletions
diff --git a/upstream/archlinux/man8/nss-myhostname.8 b/upstream/archlinux/man8/nss-myhostname.8 new file mode 100644 index 00000000..d2e92b58 --- /dev/null +++ b/upstream/archlinux/man8/nss-myhostname.8 @@ -0,0 +1,181 @@ +'\" t +.TH "NSS\-MYHOSTNAME" "8" "" "systemd 255" "nss-myhostname" +.\" ----------------------------------------------------------------- +.\" * Define some portability stuff +.\" ----------------------------------------------------------------- +.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +.\" http://bugs.debian.org/507673 +.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html +.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +.ie \n(.g .ds Aq \(aq +.el .ds Aq ' +.\" ----------------------------------------------------------------- +.\" * set default formatting +.\" ----------------------------------------------------------------- +.\" disable hyphenation +.nh +.\" disable justification (adjust text to left margin only) +.ad l +.\" ----------------------------------------------------------------- +.\" * MAIN CONTENT STARTS HERE * +.\" ----------------------------------------------------------------- +.SH "NAME" +nss-myhostname, libnss_myhostname.so.2 \- Hostname resolution for the locally configured system hostname +.SH "SYNOPSIS" +.PP +libnss_myhostname\&.so\&.2 +.SH "DESCRIPTION" +.PP +\fBnss\-myhostname\fR +is a plug\-in module 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 +\fBgethostname\fR(2)\&. The precise hostnames resolved by this module are: +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +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)\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +The hostnames +"localhost" +and +"localhost\&.localdomain" +(as well as any hostname ending in +"\&.localhost" +or +"\&.localhost\&.localdomain") are resolved to the IP addresses 127\&.0\&.0\&.1 and ::1\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +The hostname +"_gateway" +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\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +The hostname +"_outbound" +is resolved to the local IPv4 and IPv6 addresses that are most likely used for communication with other hosts\&. This is determined by requesting a routing decision to the configured default gateways from the kernel and then using the local IP addresses selected by this decision\&. This hostname is only available if there is at least one local default gateway configured\&. This assigns a stable hostname to the local outbound IP addresses, useful for referencing them independently of the current network configuration state\&. +.RE +.PP +Various software relies on an always\-resolvable local hostname\&. When using dynamic hostnames, this is traditionally achieved by patching +/etc/hosts +at the same time as changing the hostname\&. This is problematic since it requires a writable +/etc/ +file system and is fragile because the file might be edited by the administrator at the same time\&. With +\fBnss\-myhostname\fR +enabled, changing +/etc/hosts +is unnecessary, and on many systems, the file becomes entirely optional\&. +.PP +To activate the NSS modules, add +"myhostname" +to the line starting with +"hosts:" +in +/etc/nsswitch\&.conf\&. +.PP +It is recommended to place +"myhostname" +after +"file" +and before +"dns"\&. This resolves well\-known hostnames like +"localhost" +and the machine hostnames locally\&. It is consistent with the behaviour of +\fBnss\-resolve\fR, and still allows overriding via +/etc/hosts\&. +.PP +Please keep in mind that +\fBnss\-myhostname\fR +(and +\fBnss\-resolve\fR) also resolve in the other direction \(em from locally attached IP addresses to hostnames\&. If you rely on that lookup being provided by DNS, you might want to order things differently\&. +.SH "EXAMPLE" +.PP +Here is an example +/etc/nsswitch\&.conf +file that enables +\fBnss\-myhostname\fR +correctly: +.sp +.if n \{\ +.RS 4 +.\} +.nf +passwd: files systemd +group: files [SUCCESS=merge] systemd +shadow: files systemd +gshadow: files systemd + +hosts: mymachines resolve [!UNAVAIL=return] files \fBmyhostname\fR dns +networks: files + +protocols: db files +services: db files +ethers: db files +rpc: db files + +netgroup: nis +.fi +.if n \{\ +.RE +.\} +.PP +To test, use +\fBglibc\fR\*(Aqs +\fBgetent\fR(1) +tool: +.sp +.if n \{\ +.RS 4 +.\} +.nf +$ getent ahosts `hostname` +::1 STREAM omega +::1 DGRAM +::1 RAW +127\&.0\&.0\&.2 STREAM +127\&.0\&.0\&.2 DGRAM +127\&.0\&.0\&.2 RAW +.fi +.if n \{\ +.RE +.\} +.PP +In this case, the local hostname is +\fIomega\fR\&. +.SH "SEE ALSO" +.PP +\fBsystemd\fR(1), +\fBnss-systemd\fR(8), +\fBnss-resolve\fR(8), +\fBnss-mymachines\fR(8), +\fBnsswitch.conf\fR(5), +\fBgetent\fR(1) |