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
25 unsolved until Corosync. Corosync is designed for applications to
26 replicate their state to up to 16 processors. The processors all con‐
27 tain a 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
32 extended 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
49 options.
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
74 /path_to_authkey/authkey /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
82 enabled.
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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 to distros to place include files in
91 /usr/include/corosync.
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95 The corosync project supports both IPv4 and IPv6 network addresses.
96 The entire cluster must use either IPv4 or IPv6 for the cluster commu‐
97 nication mechanism. In order to use IPv6, IPv6 addresses must be spec‐
98 ified in the bindnetaddr and mcastaddr fields in the configuration
99 file. The nodeid field must also be set.
100 An example of this is: nodeid: 2 bindnetaddr: fec0::1:a800:4ff:fe00:20
102 mcastaddr: ff05::1
103 To configure a host for IPv6, use the ifconfig program to add inter‐
105 faces: box20: ifconfig eth0 add fec0::1:a800:4ff:fe00:20/64 box30:
106 ifconfig eth0 add fec0::1:a800:4ff:fe00:30/64
107 If the /64 is not specified, a route for the IPv6 network will not be
109 configured which will cause significant problems. Make sure a route is
110 available for IPv6 traffic.
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114 The corosync libraries are a thin IPC interface to the corosync execu‐
115 tive. The corosync executive implements the functionality of the
116 corosync APIs for distributed coming.
117 The corosync executive uses the Totem extended virtual synchrony proto‐
119 col. The advantage to the end user is excellent performance character‐
120 istics and a proven protocol with excellent reliability. This protocol
121 connects the processors in a configuration together so they may commu‐
122 nicate.
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126 The corosync executive optionally encrypts and signs all messages sent
127 over the network. For more details see crypto_model, crypto_hash and
128 crypto_cipher options in the corosync.conf(5).
129 If membership messages can be captured by intruders, it is possible to
131 execute a denial of service attack on the cluster. In this scenario,
132 the cluster is likely already compromised and a DOS attack is the least
133 of the administration's worries.
134 The security in corosync does not offer perfect forward secrecy because
136 the keys are reused. It may be possible for an intruder by capturing
137 packets in an automated fashion to determine the shared key. No such
138 automated attack has been published as of yet. In this scenario, the
139 cluster is likely already compromised to allow the long-term capture of
140 transmitted data.
141 For security reasons, the corosync executive binary should NEVER be
143 setuid or setgid in the filesystem.
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147 None that are known.
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151 corosync.conf(5), corosync-keygen(8), cpg_overview(3), sam_overview(3)
152corosync Man Page 2018-11-13 COROSYNC_OVERVIEW(7)