FreeBSD Manual Pages
COROS...ERVIEW(7) Corosync Cluster Engine Programmer's ManualCOROS...ERVIEW(7) NAME corosync_overview - Corosync overview OVERVIEW The corosync project's purpose is to implement and support a production quality Revised BSD licensed implementation of a high performance low overhead high availability development toolkit. Faults occur for various reasons: * Application Faults * Middleware Faults * Operating System Faults * Hardware Faults The major focus of high availability in the past has been to mask hard- ware faults. Faults in other components of the system have gone un- solved until Corosync. Corosync is designed for applications to repli- cate their state to up to 16 processors. The processors all contain a replica of the application state. The corosync project provides a group message API called CPG. The project developers recommend CPG be used for most applications. The CPG service implements a closed group messaging model presenting ex- tended virtual synchrony guarantees. To manage conditions where the process executing the CPG application exchange fails, we provide the Simple Availability Manager (sam) to provide simple application restart. QUICKSTART The corosync executive must be configured. In the directory conf in the source distribution are several files that must be copied to the /etc/corosync directory. If corosync is packaged by a distro, this may be complete. The directory contains the file corosync.conf. Please read the coro- sync.conf(5) man page for details on the configuration options. The corosync project will work out of the box with the default configura- tion options, although the administrator may desire different options. The corosync executive uses cryptographic techniques to ensure authen- ticity and privacy of the messages. In order for corosync to be secure and operate, a private key must be generated and shared to all proces- sors. First generate the key on one of the nodes: unix# corosync-keygen Corosync Cluster Engine Authentication key generator. Gathering 2048 bits for key from /dev/urandom. Writing corosync key to /etc/corosync/authkey. After this operation, a private key will be in the file /etc/coro- sync/authkey. This private key must be copied to every processor in the cluster. If the private key isn't the same for every node, those nodes with nonmatching private keys will not be able to join the same configuration. Copy the key to some security transportable storage or use ssh to transmit the key from node to node. Then install the key with the com- mand: unix#: install -D --group=0 --owner=0 --mode=0400 /path_to_authkey/au- thkey /etc/corosync/authkey If a message "Invalid digest" appears from the corosync executive, the keys are not consistent between processors. Finally run the corosync executive. If corosync is packaged from a distro, it may be set to start on system start. It may also be turned off by default in which case the init script for corosync must be en- abled. USING LIBRARIES The corosync libraries have header files which must be included in the developer's application. Once the header file is included, the devel- oper can reference the corosync interfaces. The corosync project recommends that distros place include files in /usr/include/corosync. IPv6 The corosync project supports both IPv4 and IPv6 network addresses. When using knet as the transport each link should have the same IP fam- ily, but different links can have different families (eg link 0 could be all IPv4, and link 1 all IPv6). When using UDP/UDPU the single link should use the same family on all nodes. To configure a host for IPv6, use the ifconfig program to add inter- faces: box20: ifconfig eth0 add fec0::1:a800:4ff:fe00:20/64 box30: if- config eth0 add fec0::1:a800:4ff:fe00:30/64 If the /64 is not specified, a route for the IPv6 network will not be configured which will cause significant problems. Make sure a route is available for IPv6 traffic. ARCHITECTURE The corosync libraries are a thin IPC interface to the corosync execu- tive. The corosync executive implements the functionality of the coro- sync APIs for distributed computing. The corosync executive uses the Totem extended virtual synchrony proto- col. The advantage to the end user is excellent performance character- istics and a proven protocol with excellent reliability. This protocol connects the processors in a configuration together so they may commu- nicate. SECURITY The corosync executive optionally encrypts and signs all messages sent over the network. For more details see crypto_model, crypto_hash and crypto_cipher options in the corosync.conf(5). If membership messages can be captured by intruders, it is possible to execute a denial of service attack on the cluster. In this scenario, the cluster is likely already compromised and a DoS attack is the least of the administration's worries. The security in corosync does not offer perfect forward secrecy because the keys are reused. It may be possible for an intruder to determine the shared key by capturing packets in an automated fashion. No such automated attack has been published as of yet. In this scenario, the cluster is likely already compromised to allow the long-term capture of transmitted data. For security reasons, the corosync executive binary should NEVER be se- tuid or setgid in the filesystem. BUGS None that are known. SEE ALSO corosync.conf(5), corosync-keygen(8), corosync_quorumtool(8), coro- sync_cfgtool(8), corosync_cpgtool(8), corosync_cmaptool(8), cpg_overview(3), sam_overview(3) corosync Man Page 2018-11-13 COROS...ERVIEW(7)
NAME | OVERVIEW | QUICKSTART | USING LIBRARIES | IPv6 | ARCHITECTURE | SECURITY | BUGS | SEE ALSO
Want to link to this manual page? Use this URL:
<https://man.freebsd.org/cgi/man.cgi?query=corosync_overview&sektion=7&manpath=FreeBSD+Ports+14.3.quarterly>