From 41b7beb7404c134820870ab21ae0242dfc749b2c Mon Sep 17 00:00:00 2001 From: Luke Shumaker Date: Wed, 26 Oct 2016 22:49:41 -0400 Subject: ./tools/notsd-move --- .../systemd-resolved/systemd-resolved.service.xml | 234 +++++++++++++++++++++ 1 file changed, 234 insertions(+) create mode 100644 src/grp-resolve/systemd-resolved/systemd-resolved.service.xml (limited to 'src/grp-resolve/systemd-resolved/systemd-resolved.service.xml') diff --git a/src/grp-resolve/systemd-resolved/systemd-resolved.service.xml b/src/grp-resolve/systemd-resolved/systemd-resolved.service.xml new file mode 100644 index 0000000000..aa1c2365e5 --- /dev/null +++ b/src/grp-resolve/systemd-resolved/systemd-resolved.service.xml @@ -0,0 +1,234 @@ + + + + + + + + + systemd-resolved.service + systemd + + + + Developer + Tom + Gundersen + teg@jklm.no + + + + + + systemd-resolved.service + 8 + + + + systemd-resolved.service + systemd-resolved + Network Name Resolution manager + + + + systemd-resolved.service + /usr/lib/systemd/systemd-resolved + + + + Description + + systemd-resolved is a system service that provides network name resolution to local + applications. It implements a caching and validating DNS/DNSSEC stub resolver, as well as an LLMNR resolver and + responder. Local applications may submit network name resolution requests via three interfaces: + + + The native, fully-featured API systemd-resolved exposes on the bus. See the + API Documentation for + details. Usage of this API is generally recommended to clients as it is asynchronous and fully featured (for + example, properly returns DNSSEC validation status and interface scope for addresses as necessary for supporting + link-local networking). + + The glibc + getaddrinfo3 API as defined + by RFC3493 and its related resolver functions, + including gethostbyname3. This + API is widely supported, including beyond the Linux platform. In its current form it does not expose DNSSEC + validation status information however, and is synchronous only. This API is backed by the glibc Name Service + Switch (nss5). Usage of the + glibc NSS module nss-resolve8 + is required in order to allow glibc's NSS resolver functions to resolve host names via + systemd-resolved. + + Additionally, systemd-resolved provides a local DNS stub listener on IP + address 127.0.0.53 on the local loopback interface. Programs issuing DNS requests directly, bypassing any local + API may be directed to this stub, in order to connect them to systemd-resolved. Note however + that it is strongly recommended that local programs use the glibc NSS or bus APIs instead (as described above), + as various network resolution concepts (such as link-local addressing, or LLMNR Unicode domains) cannot be mapped + to the unicast DNS protocol. + + + The DNS servers contacted are determined from the global settings in + /etc/systemd/resolved.conf, the per-link static settings in + /etc/systemd/network/*.network files, the per-link dynamic settings received over DHCP and any + DNS server information made available by other system services. See + resolved.conf5 and + systemd.network5 for details + about systemd's own configuration files for DNS servers. To improve compatibility, + /etc/resolv.conf is read in order to discover configured system DNS servers, but only if it is + not a symlink to /run/systemd/resolve/resolv.conf (see below). + + systemd-resolved synthesizes DNS resource records (RRs) for the following cases: + + + The local, configured hostname is resolved to + all locally configured IP addresses ordered by their scope, or + — if none are configured — the IPv4 address 127.0.0.2 (which + is on the local loopback) and the IPv6 address ::1 (which is the + local host). + + 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. + + 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. + + The mappings defined in /etc/hosts are resolved to their configured + addresses and back. + + + Lookup requests are routed to the available DNS servers + and LLMNR interfaces according to the following rules: + + + Lookups for the special hostname + localhost are never routed to the + network. (A few other, special domains are handled the same way.) + + Single-label names are routed to all local + interfaces capable of IP multicasting, using the LLMNR + protocol. Lookups for IPv4 addresses are only sent via LLMNR on + IPv4, and lookups for IPv6 addresses are only sent via LLMNR on + IPv6. Lookups for the locally configured host name and the + gateway host name are never routed to + LLMNR. + + Multi-label names are routed to all local + interfaces that have a DNS sever configured, plus the globally + configured DNS server if there is one. Address lookups from the + link-local address range are never routed to + DNS. + + + If lookups are routed to multiple interfaces, the first + successful response is returned (thus effectively merging the + lookup zones on all matching interfaces). If the lookup failed on + all interfaces, the last failing response is returned. + + Routing of lookups may be influenced by configuring + per-interface domain names. See + systemd.network5 + for details. Lookups for a hostname ending in one of the + per-interface domains are exclusively routed to the matching + interfaces. + + See the resolved D-Bus API + Documentation for information about the APIs systemd-resolved provides. + + + + + <filename>/etc/resolv.conf</filename> + + Three modes of handling /etc/resolv.conf (see + resolv.conf5) are + supported: + + + A static file /usr/lib/systemd/resolv.conf is provided that lists + the 127.0.0.53 DNS stub (see above) as only DNS server. This file may be symlinked from + /etc/resolv.conf in order to connect all local clients that bypass local DNS APIs to + systemd-resolved. This mode of operation is recommended. + + systemd-resolved maintains the + /run/systemd/resolve/resolv.conf file for compatibility with traditional Linux + programs. This file may be symlinked from /etc/resolv.conf and is always kept up-to-date, + containing information about all known DNS servers. Note the file format's limitations: it does not know a + concept of per-interface DNS servers and hence only contains system-wide DNS server definitions. Note that + /run/systemd/resolve/resolv.conf should not be used directly by applications, but only + through a symlink from /etc/resolv.conf. If this mode of operation is used local clients + that bypass any local DNS API will also bypass systemd-resolved and will talk directly to the + known DNS servers. + + Alternatively, /etc/resolv.conf may be managed by other packages, in which + case systemd-resolved will read it for DNS configuration data. In this mode of operation + systemd-resolved is consumer rather than provider of this configuration + file. + + + Note that the selected mode of operation for this file is detected fully automatically, depending on whether + /etc/resolv.conf is a symlink to /run/systemd/resolve/resolv.conf or + lists 127.0.0.53 as DNS server. + + + + Signals + + + + SIGUSR1 + + Upon reception of the SIGUSR1 process signal systemd-resolved will dump the + contents of all DNS resource record caches it maintains into the system logs. + + + + SIGUSR2 + + Upon reception of the SIGUSR2 process signal systemd-resolved will flush all + caches it maintains. Note that it should normally not be necessary to request this explicitly – except for + debugging purposes – as systemd-resolved flushes the caches automatically anyway any time + the host's network configuration changes. + + + + + + See Also + + systemd1, + resolved.conf5, + dnssec-trust-anchors.d5, + nss-resolve8, + systemd-resolve1, + resolv.conf5, + hosts5, + systemd.network5, + systemd-networkd.service8 + + + + -- cgit v1.2.3-54-g00ecf