1COROSYNC_OVERVIEW(7C)orosync Cluster Engine Programmer's ManuCaOlROSYNC_OVERVIEW(7)
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6 corosync_overview - Corosync overview
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9 The corosync project's purpose is to implement and support a production
10 quality Revised BSD licensed implementation of a high performance low
11 overhead high availability development toolkit.
12 Faults occur for various reasons:
14 * Application Faults
16 * Middleware Faults
18 * Operating System Faults
20 * Hardware Faults
22 The major focus of high availability in the past has been to mask hard‐
24 ware faults. Faults in other components of the system have gone un‐
25 solved until Corosync. Corosync is designed for applications to repli‐
26 cate their state to up to 16 processors. The processors all contain a
27 replica of the application state.
28 The corosync project provides a group message API called CPG. The
30 project developers recommend CPG be used for most applications. The
31 CPG service implements a closed group messaging model presenting ex‐
32 tended virtual synchrony guarantees.
33 To manage conditions where the process executing the CPG application
35 exchange fails, we provide the Simple Availability Manager (sam) to
36 provide simple application restart.
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40 The corosync executive must be configured. In the directory conf in
41 the source distribution are several files that must be copied to the
42 /etc/corosync directory. If corosync is packaged by a distro, this may
43 be complete.
44 The directory contains the file corosync.conf. Please read the
46 corosync.conf(5) man page for details on the configuration options.
47 The corosync project will work out of the box with the default configu‐
48 ration options, although the administrator may desire different op‐
49 tions.
50 The corosync executive uses cryptographic techniques to ensure authen‐
52 ticity and privacy of the messages. In order for corosync to be secure
53 and operate, a private key must be generated and shared to all proces‐
54 sors.
55 First generate the key on one of the nodes:
57 unix# corosync-keygen
59 Corosync Cluster Engine Authentication key generator.
60 Gathering 2048 bits for key from /dev/urandom.
61 Writing corosync key to /etc/corosync/authkey.
62 After this operation, a private key will be in the file
64 /etc/corosync/authkey. This private key must be copied to every pro‐
65 cessor in the cluster. If the private key isn't the same for every
66 node, those nodes with nonmatching private keys will not be able to
67 join the same configuration.
68 Copy the key to some security transportable storage or use ssh to
70 transmit the key from node to node. Then install the key with the com‐
71 mand:
72 unix#: install -D --group=0 --owner=0 --mode=0400 /path_to_authkey/au‐
74 thkey /etc/corosync/authkey
75 If a message "Invalid digest" appears from the corosync executive, the
77 keys are not consistent between processors.
78 Finally run the corosync executive. If corosync is packaged from a
80 distro, it may be set to start on system start. It may also be turned
81 off by default in which case the init script for corosync must be en‐
82 abled.
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86 The corosync libraries have header files which must be included in the
87 developer's application. Once the header file is included, the devel‐
88 oper can reference the corosync interfaces.
89 The corosync project recommends that distros place include files in
91 /usr/include/corosync.
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95 The corosync project supports both IPv4 and IPv6 network addresses.
96 When using knet as the transport each link should have the same IP fam‐
97 ily, but different links can have different families (eg link 0 could
98 be all IPv4, and link 1 all IPv6). When using UDP/UDPU the single link
99 should use the same family on all nodes.
100 To configure a host for IPv6, use the ifconfig program to add inter‐
102 faces: box20: ifconfig eth0 add fec0::1:a800:4ff:fe00:20/64 box30: if‐
103 config eth0 add fec0::1:a800:4ff:fe00:30/64
104 If the /64 is not specified, a route for the IPv6 network will not be
106 configured which will cause significant problems. Make sure a route is
107 available for IPv6 traffic.
108
111 The corosync libraries are a thin IPC interface to the corosync execu‐
112 tive. The corosync executive implements the functionality of the
113 corosync APIs for distributed computing.
114 The corosync executive uses the Totem extended virtual synchrony proto‐
116 col. The advantage to the end user is excellent performance character‐
117 istics and a proven protocol with excellent reliability. This protocol
118 connects the processors in a configuration together so they may commu‐
119 nicate.
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123 The corosync executive optionally encrypts and signs all messages sent
124 over the network. For more details see crypto_model, crypto_hash and
125 crypto_cipher options in the corosync.conf(5).
126 If membership messages can be captured by intruders, it is possible to
128 execute a denial of service attack on the cluster. In this scenario,
129 the cluster is likely already compromised and a DoS attack is the least
130 of the administration's worries.
131 The security in corosync does not offer perfect forward secrecy because
133 the keys are reused. It may be possible for an intruder to determine
134 the shared key by capturing packets in an automated fashion. No such
135 automated attack has been published as of yet. In this scenario, the
136 cluster is likely already compromised to allow the long-term capture of
137 transmitted data.
138 For security reasons, the corosync executive binary should NEVER be se‐
140 tuid or setgid in the filesystem.
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144 None that are known.
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148 corosync.conf(5), corosync-keygen(8), corosync_quorumtool(8),
149 corosync_cfgtool(8), corosync_cpgtool(8), corosync_cmaptool(8),
150 cpg_overview(3), sam_overview(3)
151corosync Man Page 2018-11-13 COROSYNC_OVERVIEW(7)