diff --git a/doc/Clusters_from_Scratch/en-US/Ch-Installation.txt b/doc/Clusters_from_Scratch/en-US/Ch-Installation.txt index af50405594..8861dedf74 100644 --- a/doc/Clusters_from_Scratch/en-US/Ch-Installation.txt +++ b/doc/Clusters_from_Scratch/en-US/Ch-Installation.txt @@ -1,514 +1,557 @@ :compat-mode: legacy = Installation = == Install &DISTRO; &DISTRO_VERSION; == === Boot the Install Image === Download the 4GB http://isoredirect.centos.org/centos/7/isos/x86_64/CentOS-7-x86_64-DVD-1804.iso[&DISTRO; &DISTRO_VERSION; DVD ISO]. Use the image to boot a virtual machine, or burn it to a DVD or USB drive and boot a physical server from that. After starting the installation, select your language and keyboard layout at the welcome screen. .&DISTRO; &DISTRO_VERSION; Installation Welcome Screen image::images/Welcome.png["Welcome to &DISTRO; &DISTRO_VERSION;",align="center",scaledwidth="100%"] === Installation Options === At this point, you get a chance to tweak the default installation options. .&DISTRO; &DISTRO_VERSION; Installation Summary Screen image::images/Installer.png["&DISTRO; &DISTRO_VERSION; Installation Summary",align="center",scaledwidth="100%"] Ignore the *SOFTWARE SELECTION* section (try saying that 10 times quickly). The *Infrastructure Server* environment does have add-ons with much of the software we need, but we will leave it as a *Minimal Install* here, so that we can see exactly what software is required later. === Configure Network === In the *NETWORK & HOSTNAME* section: - Edit *Host Name:* as desired. For this example, we will use *pcmk-1.localdomain*. - Select your network device, press *Configure...*, and manually assign a fixed IP address. For this example, we'll use 192.168.122.101 under *IPv4 Settings* (with an appropriate netmask, gateway and DNS server). - Flip the switch to turn your network device on, and press *Done*. .&DISTRO; &DISTRO_VERSION; Network Interface Screen image::images/Editing-eth0.png["&DISTRO; &DISTRO_VERSION; Editing eth0",align="center",scaledwidth="100%"] [IMPORTANT] =========== Do not accept the default network settings. Cluster machines should never obtain an IP address via DHCP, because DHCP's periodic address renewal will interfere with corosync. =========== === Configure Disk === By default, the installer's automatic partitioning will use LVM (which allows us to dynamically change the amount of space allocated to a given partition). However, it allocates all free space to the +/+ (aka. *root*) partition, which cannot be reduced in size later (dynamic increases are fine). In order to follow the DRBD and GFS2 portions of this guide, we need to reserve space on each machine for a replicated volume. Enter the *INSTALLATION DESTINATION* section, ensure the hard drive you want to install to is selected, select *I will configure partitioning*, and press *Done*. In the *MANUAL PARTITIONING* screen that comes next, click the option to create mountpoints automatically. Select the +/+ mountpoint, and reduce the desired capacity by 1GiB or so. Select *Modify...* by the volume group name, and change the *Size policy:* to *As large as possible*, to make the reclaimed space available inside the LVM volume group. We'll add the additional volume later. .&DISTRO; &DISTRO_VERSION; Manual Partitioning Screen image::images/Partitioning.png["&DISTRO; &DISTRO_VERSION; Partitioning",align="center",scaledwidth="100%"] Press *Done*, then *Accept changes*. === Configure Time Synchronization === It is highly recommended to enable NTP on your cluster nodes. Doing so ensures all nodes agree on the current time and makes reading log files significantly easier. &DISTRO; will enable NTP automatically. If you want to change any time-related settings (such as time zone or NTP server), you can do this in the *TIME & DATE* section. === Finish Install === Select *Begin Installation*. Once it completes, set a root password, and reboot as instructed. For the purposes of this document, it is not necessary to create any additional users. After the node reboots, you'll see a login prompt on the console. Login using *root* and the password you created earlier. .&DISTRO; &DISTRO_VERSION; Console Prompt image::images/Console.png["&DISTRO; &DISTRO_VERSION; Console",align="center",scaledwidth="100%"] [NOTE] ====== From here on, we're going to be working exclusively from the terminal. ====== == Configure the OS == === Verify Networking === Ensure that the machine has the static IP address you configured earlier. ----- [root@pcmk-1 ~]# ip addr 1: lo: mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eth0: mtu 1500 qdisc pfifo_fast state UP group default qlen 1000 link/ether 52:54:00:8e:eb:41 brd ff:ff:ff:ff:ff:ff inet 192.168.122.101/24 brd 192.168.122.255 scope global noprefixroute eth0 valid_lft forever preferred_lft forever inet6 fe80::e45:c99b:34c0:c657/64 scope link noprefixroute valid_lft forever preferred_lft forever ----- [NOTE] ===== If you ever need to change the node's IP address from the command line, follow these instructions, replacing *${device}* with the name of your network device: .... [root@pcmk-1 ~]# vi /etc/sysconfig/network-scripts/ifcfg-${device} # manually edit as desired [root@pcmk-1 ~]# nmcli dev disconnect ${device} [root@pcmk-1 ~]# nmcli con reload ${device} [root@pcmk-1 ~]# nmcli con up ${device} .... This makes *NetworkManager* aware that a change was made on the config file. ===== Next, ensure that the routes are as expected: ----- [root@pcmk-1 ~]# ip route default via 192.168.122.1 dev eth0 proto static metric 100 192.168.122.0/24 dev eth0 proto kernel scope link src 192.168.122.101 metric 100 ----- If there is no line beginning with *default via*, then you may need to add a line such as [source,Bash] GATEWAY="192.168.122.1" to the device configuration using the same process as described above for changing the IP address. Now, check for connectivity to the outside world. Start small by testing whether we can reach the gateway we configured. ----- [root@pcmk-1 ~]# ping -c 1 192.168.122.1 PING 192.168.122.1 (192.168.122.1) 56(84) bytes of data. 64 bytes from 192.168.122.1: icmp_seq=1 ttl=64 time=0.254 ms --- 192.168.122.1 ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 0.254/0.254/0.254/0.000 ms ----- Now try something external; choose a location you know should be available. ----- [root@pcmk-1 ~]# ping -c 1 www.clusterlabs.org PING oss-uk-1.clusterlabs.org (109.74.197.241) 56(84) bytes of data. 64 bytes from oss-uk-1.clusterlabs.org (109.74.197.241): icmp_seq=1 ttl=49 time=333 ms --- oss-uk-1.clusterlabs.org ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 333.204/333.204/333.204/0.000 ms ----- === Login Remotely === The console isn't a very friendly place to work from, so we will now switch to accessing the machine remotely via SSH where we can use copy and paste, etc. From another host, check whether we can see the new host at all: ----- beekhof@f16 ~ # ping -c 1 192.168.122.101 PING 192.168.122.101 (192.168.122.101) 56(84) bytes of data. 64 bytes from 192.168.122.101: icmp_req=1 ttl=64 time=1.01 ms --- 192.168.122.101 ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 1.012/1.012/1.012/0.000 ms ----- Next, login as root via SSH. ----- beekhof@f16 ~ # ssh -l root 192.168.122.101 The authenticity of host '192.168.122.101 (192.168.122.101)' can't be established. ECDSA key fingerprint is 6e:b7:8f:e2:4c:94:43:54:a8:53:cc:20:0f:29:a4:e0. Are you sure you want to continue connecting (yes/no)? yes Warning: Permanently added '192.168.122.101' (ECDSA) to the list of known hosts. root@192.168.122.101's password: Last login: Tue Aug 11 13:14:39 2015 [root@pcmk-1 ~]# ----- === Apply Updates === Apply any package updates released since your installation image was created: ---- [root@pcmk-1 ~]# yum update ---- === Use Short Node Names === During installation, we filled in the machine's fully qualified domain name (FQDN), which can be rather long when it appears in cluster logs and status output. See for yourself how the machine identifies itself: (((Nodes, short name))) ---- [root@pcmk-1 ~]# uname -n pcmk-1.localdomain ---- (((Nodes, Domain name (Query)))) We can use the `hostnamectl` tool to strip off the domain name: ---- [root@pcmk-1 ~]# hostnamectl set-hostname $(uname -n | sed s/\\..*//) ---- (((Nodes, Domain name (Remove from host name)))) Now, check that the machine is using the correct name: ---- [root@pcmk-1 ~]# uname -n pcmk-1 ---- You may want to reboot to ensure all updates take effect. == Repeat for Second Node == Repeat the Installation steps so far, so that you have two nodes ready to have the cluster software installed. For the purposes of this document, the additional node is called pcmk-2 with address 192.168.122.102. == Configure Communication Between Nodes == === Configure Host Name Resolution === Confirm that you can communicate between the two new nodes: ---- [root@pcmk-1 ~]# ping -c 3 192.168.122.102 PING 192.168.122.102 (192.168.122.102) 56(84) bytes of data. 64 bytes from 192.168.122.102: icmp_seq=1 ttl=64 time=0.343 ms 64 bytes from 192.168.122.102: icmp_seq=2 ttl=64 time=0.402 ms 64 bytes from 192.168.122.102: icmp_seq=3 ttl=64 time=0.558 ms --- 192.168.122.102 ping statistics --- 3 packets transmitted, 3 received, 0% packet loss, time 2000ms rtt min/avg/max/mdev = 0.343/0.434/0.558/0.092 ms ---- Now we need to make sure we can communicate with the machines by their name. If you have a DNS server, add additional entries for the two machines. Otherwise, you'll need to add the machines to +/etc/hosts+ on both nodes. Below are the entries for my cluster nodes: ---- [root@pcmk-1 ~]# grep pcmk /etc/hosts 192.168.122.101 pcmk-1.clusterlabs.org pcmk-1 192.168.122.102 pcmk-2.clusterlabs.org pcmk-2 ---- We can now verify the setup by again using ping: ---- [root@pcmk-1 ~]# ping -c 3 pcmk-2 PING pcmk-2.clusterlabs.org (192.168.122.101) 56(84) bytes of data. 64 bytes from pcmk-1.clusterlabs.org (192.168.122.101): icmp_seq=1 ttl=64 time=0.164 ms 64 bytes from pcmk-1.clusterlabs.org (192.168.122.101): icmp_seq=2 ttl=64 time=0.475 ms 64 bytes from pcmk-1.clusterlabs.org (192.168.122.101): icmp_seq=3 ttl=64 time=0.186 ms --- pcmk-2.clusterlabs.org ping statistics --- 3 packets transmitted, 3 received, 0% packet loss, time 2001ms rtt min/avg/max/mdev = 0.164/0.275/0.475/0.141 ms ---- === Configure SSH === SSH is a convenient and secure way to copy files and perform commands remotely. For the purposes of this guide, we will create a key without a password (using the -N option) so that we can perform remote actions without being prompted. (((SSH))) [WARNING] ========= Unprotected SSH keys (those without a password) are not recommended for servers exposed to the outside world. We use them here only to simplify the demo. ========= Create a new key and allow anyone with that key to log in: .Creating and Activating a new SSH Key ---- [root@pcmk-1 ~]# ssh-keygen -t dsa -f ~/.ssh/id_dsa -N "" Generating public/private dsa key pair. Your identification has been saved in /root/.ssh/id_dsa. Your public key has been saved in /root/.ssh/id_dsa.pub. The key fingerprint is: 91:09:5c:82:5a:6a:50:08:4e:b2:0c:62:de:cc:74:44 root@pcmk-1.clusterlabs.org The key's randomart image is: +--[ DSA 1024]----+ |==.ooEo.. | |X O + .o o | | * A + | | + . | | . S | | | | | | | | | +-----------------+ [root@pcmk-1 ~]# cp ~/.ssh/id_dsa.pub ~/.ssh/authorized_keys ---- (((Creating and Activating a new SSH Key))) Install the key on the other node: ---- [root@pcmk-1 ~]# scp -r ~/.ssh pcmk-2: The authenticity of host 'pcmk-2 (192.168.122.102)' can't be established. ECDSA key fingerprint is SHA256:63xNPkPYq98rYznf3T9QYJAzlaGiAsSgFVNHOZjPWqc. ECDSA key fingerprint is MD5:d9:bf:6e:32:88:be:47:3d:96:f1:96:27:65:05:0b:c3. Are you sure you want to continue connecting (yes/no)? yes Warning: Permanently added 'pcmk-2,192.168.122.102' (ECDSA) to the list of known hosts. root@pcmk-2's password: id_dsa id_dsa.pub authorized_keys known_hosts ---- Test that you can now run commands remotely, without being prompted: ---- [root@pcmk-1 ~]# ssh pcmk-2 -- uname -n pcmk-2 ---- == Install the Cluster Software == Fire up a shell on both nodes and run the following to install pacemaker, and while we're at it, some command-line tools to make our lives easier: ---- # yum install -y pacemaker pcs psmisc policycoreutils-python ---- [IMPORTANT] =========== This document will show commands that need to be executed on both nodes with a simple `#` prompt. Be sure to run them on each node individually. =========== [NOTE] =========== This document uses `pcs` for cluster management. Other alternatives, such as `crmsh`, are available, but their syntax will differ from the examples used here. =========== == Configure the Cluster Software == === Allow cluster services through firewall === On each node, allow cluster-related services through the local firewall: ---- # firewall-cmd --permanent --add-service=high-availability success # firewall-cmd --reload success ---- [NOTE] ====== If you are using iptables directly, or some other firewall solution besides firewalld, simply open the following ports, which can be used by various clustering components: TCP ports 2224, 3121, and 21064, and UDP port 5405. If you run into any problems during testing, you might want to disable the firewall and SELinux entirely until you have everything working. This may create significant security issues and should not be performed on machines that will be exposed to the outside world, but may be appropriate during development and testing on a protected host. To disable security measures: ---- [root@pcmk-1 ~]# setenforce 0 [root@pcmk-1 ~]# sed -i.bak "s/SELINUX=enforcing/SELINUX=permissive/g" /etc/selinux/config [root@pcmk-1 ~]# systemctl mask firewalld.service [root@pcmk-1 ~]# systemctl stop firewalld.service [root@pcmk-1 ~]# iptables --flush ---- ====== === Enable pcs Daemon === Before the cluster can be configured, the pcs daemon must be started and enabled to start at boot time on each node. This daemon works with the pcs command-line interface to manage synchronizing the corosync configuration across all nodes in the cluster. Start and enable the daemon by issuing the following commands on each node: ---- # systemctl start pcsd.service # systemctl enable pcsd.service Created symlink from /etc/systemd/system/multi-user.target.wants/pcsd.service to /usr/lib/systemd/system/pcsd.service. ---- The installed packages will create a *hacluster* user with a disabled password. While this is fine for running `pcs` commands locally, the account needs a login password in order to perform such tasks as syncing the corosync configuration, or starting and stopping the cluster on other nodes. This tutorial will make use of such commands, so now we will set a password for the *hacluster* user, using the same password on both nodes: ---- # passwd hacluster Changing password for user hacluster. New password: Retype new password: passwd: all authentication tokens updated successfully. ---- [NOTE] =========== Alternatively, to script this process or set the password on a different machine from the one you're logged into, you can use the `--stdin` option for `passwd`: ---- [root@pcmk-1 ~]# ssh pcmk-2 -- 'echo mysupersecretpassword | passwd --stdin hacluster' ---- =========== === Configure Corosync === On either node, use `pcs cluster auth` to authenticate as the *hacluster* user: ---- [root@pcmk-1 ~]# pcs cluster auth pcmk-1 pcmk-2 Username: hacluster Password: pcmk-2: Authorized pcmk-1: Authorized ---- +.Note +[NOTE] +==== +In Fedora 29 and CentOS 8.0, the command has been changed to `pcs host auth`: +---- +[root@pcmk-1 ~]# pcs host auth pcmk-1 pcmk-2 +Username: hacluster +Password: +pcmk-2: Authorized +pcmk-1: Authorized +---- +==== + Next, use `pcs cluster setup` on the same node to generate and synchronize the corosync configuration: ---- [root@pcmk-1 ~]# pcs cluster setup --name mycluster pcmk-1 pcmk-2 Destroying cluster on nodes: pcmk-1, pcmk-2... pcmk-2: Stopping Cluster (pacemaker)... pcmk-1: Stopping Cluster (pacemaker)... pcmk-1: Successfully destroyed cluster pcmk-2: Successfully destroyed cluster Sending 'pacemaker_remote authkey' to 'pcmk-1', 'pcmk-2' pcmk-2: successful distribution of the file 'pacemaker_remote authkey' pcmk-1: successful distribution of the file 'pacemaker_remote authkey' Sending cluster config files to the nodes... pcmk-1: Succeeded pcmk-2: Succeeded Synchronizing pcsd certificates on nodes pcmk-1, pcmk-2... pcmk-2: Success pcmk-1: Success Restarting pcsd on the nodes in order to reload the certificates... pcmk-2: Success pcmk-1: Success ---- +.Note +[NOTE] +==== +In Fedora 29 and CentOS 8.0, the syntax has been changed and the +--name+ option +has been dropped: +---- +[root@pcmk-1 ~]# pcs cluster setup mycluster pcmk-1 pcmk-2 +No addresses specified for host 'pcmk-1', using 'pcmk-1' +No addresses specified for host 'pcmk-2', using 'pcmk-2' +Destroying cluster on hosts: 'pcmk-1', 'pcmk-2'... +pcmk-1: Successfully destroyed cluster +pcmk-2: Successfully destroyed cluster +Requesting remove 'pcsd settings' from 'pcmk-1', 'pcmk-2' +pcmk-1: successful removal of the file 'pcsd settings' +pcmk-2: successful removal of the file 'pcsd settings' +Sending 'corosync authkey', 'pacemaker authkey' to 'pcmk-1', 'pcmk-2' +pcmk-2: successful distribution of the file 'corosync authkey' +pcmk-2: successful distribution of the file 'pacemaker authkey' +pcmk-1: successful distribution of the file 'corosync authkey' +pcmk-1: successful distribution of the file 'pacemaker authkey' +Synchronizing pcsd SSL certificates on nodes 'pcmk-1', 'pcmk-2'... +pcmk-1: Success +pcmk-2: Success +Sending 'corosync.conf' to 'pcmk-1', 'pcmk-2' +pcmk-2: successful distribution of the file 'corosync.conf' +pcmk-1: successful distribution of the file 'corosync.conf' +Cluster has been successfully set up. +---- +==== + If you received an authorization error for either of those commands, make sure you configured the *hacluster* user account on each node with the same password. [NOTE] ====== If you are not using `pcs` for cluster administration, follow whatever procedures are appropriate for your tools to create a corosync.conf and copy it to all nodes. The `pcs` command will configure corosync to use UDP unicast transport; if you choose to use multicast instead, choose a multicast address carefully. footnote:[For some subtle issues, see http://web.archive.org/web/20101211210054/http://29west.com/docs/THPM/multicast-address-assignment.html[Topics in High-Performance Messaging: Multicast Address Assignment] or the more detailed treatment in https://www.cisco.com/c/dam/en/us/support/docs/ip/ip-multicast/ipmlt_wp.pdf[Cisco's Guidelines for Enterprise IP Multicast Address Allocation].] ====== The final corosync.conf configuration on each node should look something like the sample in <>. diff --git a/doc/Clusters_from_Scratch/en-US/Ch-Shared-Storage.txt b/doc/Clusters_from_Scratch/en-US/Ch-Shared-Storage.txt index 24eb26029f..f9287da3cf 100644 --- a/doc/Clusters_from_Scratch/en-US/Ch-Shared-Storage.txt +++ b/doc/Clusters_from_Scratch/en-US/Ch-Shared-Storage.txt @@ -1,584 +1,614 @@ :compat-mode: legacy = Replicate Storage Using DRBD = Even if you're serving up static websites, having to manually synchronize the contents of that website to all the machines in the cluster is not ideal. For dynamic websites, such as a wiki, it's not even an option. Not everyone care afford network-attached storage, but somehow the data needs to be kept in sync. Enter DRBD, which can be thought of as network-based RAID-1. footnote:[See http://www.drbd.org/ for details.] == Install the DRBD Packages == DRBD itself is included in the upstream kernel,footnote:[Since version 2.6.33] but we do need some utilities to use it effectively. CentOS does not ship these utilities, so we need to enable a third-party repository to get them. Supported packages for many OSes are available from DRBD's maker http://www.linbit.com/[LINBIT], but here we'll use the free http://elrepo.org/[ELRepo] repository. On both nodes, import the ELRepo package signing key, and enable the repository: ---- # rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org # rpm -Uvh http://www.elrepo.org/elrepo-release-7.0-3.el7.elrepo.noarch.rpm Retrieving http://www.elrepo.org/elrepo-release-7.0-3.el7.elrepo.noarch.rpm Preparing... ################################# [100%] Updating / installing... 1:elrepo-release-7.0-3.el7.elrepo ################################# [100%] ---- Now, we can install the DRBD kernel module and utilities: ---- # yum install -y kmod-drbd84 drbd84-utils ---- DRBD will not be able to run under the default SELinux security policies. If you are familiar with SELinux, you can modify the policies in a more fine-grained manner, but here we will simply exempt DRBD processes from SELinux control: ---- # semanage permissive -a drbd_t ---- We will configure DRBD to use port 7789, so allow that port from each host to the other: ---- [root@pcmk-1 ~]# firewall-cmd --permanent --add-rich-rule='rule family="ipv4" \ source address="192.168.122.102" port port="7789" protocol="tcp" accept' success [root@pcmk-1 ~]# firewall-cmd --reload success ---- ---- [root@pcmk-2 ~]# firewall-cmd --permanent --add-rich-rule='rule family="ipv4" \ source address="192.168.122.101" port port="7789" protocol="tcp" accept' success [root@pcmk-2 ~]# firewall-cmd --reload success ---- [NOTE] ====== In this example, we have only two nodes, and all network traffic is on the same LAN. In production, it is recommended to use a dedicated, isolated network for cluster-related traffic, so the firewall configuration would likely be different; one approach would be to add the dedicated network interfaces to the trusted zone. ====== == Allocate a Disk Volume for DRBD == DRBD will need its own block device on each node. This can be a physical disk partition or logical volume, of whatever size you need for your data. For this document, we will use a 512MiB logical volume, which is more than sufficient for a single HTML file and (later) GFS2 metadata. ---- [root@pcmk-1 ~]# vgdisplay | grep -e Name -e Free VG Name centos_pcmk-1 Free PE / Size 255 / 1020.00 MiB [root@pcmk-1 ~]# lvcreate --name drbd-demo --size 512M centos_pcmk-1 Logical volume "drbd-demo" created. [root@pcmk-1 ~]# lvs LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert drbd-demo centos_pcmk-1 -wi-a----- 512.00m root centos_pcmk-1 -wi-ao---- 3.00g swap centos_pcmk-1 -wi-ao---- 1.00g ---- Repeat for the second node, making sure to use the same size: ---- [root@pcmk-1 ~]# ssh pcmk-2 -- lvcreate --name drbd-demo --size 512M centos_pcmk-2 Logical volume "drbd-demo" created. ---- == Configure DRBD == There is no series of commands for building a DRBD configuration, so simply run this on both nodes to use this sample configuration: ---- # cat </etc/drbd.d/wwwdata.res resource wwwdata { protocol C; meta-disk internal; device /dev/drbd1; syncer { verify-alg sha1; } net { allow-two-primaries; } on pcmk-1 { disk /dev/centos_pcmk-1/drbd-demo; address 192.168.122.101:7789; } on pcmk-2 { disk /dev/centos_pcmk-2/drbd-demo; address 192.168.122.102:7789; } } END ---- [IMPORTANT] ========= Edit the file to use the hostnames, IP addresses and logical volume paths of your nodes if they differ from the ones used in this guide. ========= [NOTE] ======= Detailed information on the directives used in this configuration (and other alternatives) is available in the https://docs.linbit.com/docs/users-guide-8.4/#ch-configure[DRBD User's Guide]. The *allow-two-primaries* option would not normally be used in an active/passive cluster. We are adding it here for the convenience of changing to an active/active cluster later. ======= == Initialize DRBD == With the configuration in place, we can now get DRBD running. These commands create the local metadata for the DRBD resource, ensure the DRBD kernel module is loaded, and bring up the DRBD resource. Run them on one node: ---- [root@pcmk-1 ~]# drbdadm create-md wwwdata --== Thank you for participating in the global usage survey ==-- The server's response is: you are the 2147th user to install this version initializing activity log initializing bitmap (16 KB) to all zero Writing meta data... New drbd meta data block successfully created. success [root@pcmk-1 ~]# modprobe drbd [root@pcmk-1 ~]# drbdadm up wwwdata --== Thank you for participating in the global usage survey ==-- The server's response is: ---- We can confirm DRBD's status on this node: ---- [root@pcmk-1 ~]# cat /proc/drbd version: 8.4.11-1 (api:1/proto:86-101) GIT-hash: 66145a308421e9c124ec391a7848ac20203bb03c build by mockbuild@, 2018-04-26 12:10:42 1: cs:WFConnection ro:Secondary/Unknown ds:Inconsistent/DUnknown C r----s ns:0 nr:0 dw:0 dr:0 al:8 bm:0 lo:0 pe:0 ua:0 ap:0 ep:1 wo:f oos:524236 ---- Because we have not yet initialized the data, this node's data is marked as *Inconsistent*. Because we have not yet initialized the second node, the local state is *WFConnection* (waiting for connection), and the partner node's status is marked as *Unknown*. Now, repeat the above commands on the second node, starting with creating wwwdata.res. After giving it time to connect, when we check the status, it shows: ---- [root@pcmk-2 ~]# cat /proc/drbd version: 8.4.11-1 (api:1/proto:86-101) GIT-hash: 66145a308421e9c124ec391a7848ac20203bb03c build by mockbuild@, 2018-04-26 12:10:42 1: cs:Connected ro:Secondary/Secondary ds:Inconsistent/Inconsistent C r----- ns:0 nr:0 dw:0 dr:0 al:8 bm:0 lo:0 pe:0 ua:0 ap:0 ep:1 wo:f oos:524236 ---- You can see the state has changed to *Connected*, meaning the two DRBD nodes are communicating properly, and both nodes are in *Secondary* role with *Inconsistent* data. To make the data consistent, we need to tell DRBD which node should be considered to have the correct data. In this case, since we are creating a new resource, both have garbage, so we'll just pick pcmk-1 and run this command on it: ---- [root@pcmk-1 ~]# drbdadm primary --force wwwdata ---- [NOTE] ====== If you are using a different version of DRBD, the required syntax may be different. See the documentation for your version for how to perform these commands. ====== If we check the status immediately, we'll see something like this: ---- [root@pcmk-1 ~]# cat /proc/drbd version: 8.4.11-1 (api:1/proto:86-101) GIT-hash: 66145a308421e9c124ec391a7848ac20203bb03c build by mockbuild@, 2018-04-26 12:10:42 1: cs:SyncSource ro:Primary/Secondary ds:UpToDate/Inconsistent C r----- ns:43184 nr:0 dw:0 dr:45312 al:8 bm:0 lo:0 pe:0 ua:0 ap:0 ep:1 wo:f oos:481052 [>...................] sync'ed: 8.6% (481052/524236)K finish: 0:01:51 speed: 4,316 (4,316) K/sec ---- We can see that this node has the *Primary* role, the partner node has the *Secondary* role, this node's data is now considered *UpToDate*, the partner node's data is still *Inconsistent*, and a progress bar shows how far along the partner node is in synchronizing the data. After a while, the sync should finish, and you'll see something like: ---- [root@pcmk-1 ~]# cat /proc/drbd version: 8.4.11-1 (api:1/proto:86-101) GIT-hash: 66145a308421e9c124ec391a7848ac20203bb03c build by mockbuild@, 2018-04-26 12:10:42 1: cs:Connected ro:Primary/Secondary ds:UpToDate/UpToDate C r----- ns:524236 nr:0 dw:0 dr:526364 al:8 bm:0 lo:0 pe:0 ua:0 ap:0 ep:1 wo:f oos:0 ---- Both sets of data are now *UpToDate*, and we can proceed to creating and populating a filesystem for our WebSite resource's documents. == Populate the DRBD Disk == On the node with the primary role (pcmk-1 in this example), create a filesystem on the DRBD device: ---- [root@pcmk-1 ~]# mkfs.xfs /dev/drbd1 meta-data=/dev/drbd1 isize=512 agcount=4, agsize=32765 blks = sectsz=512 attr=2, projid32bit=1 = crc=1 finobt=0, sparse=0 data = bsize=4096 blocks=131059, imaxpct=25 = sunit=0 swidth=0 blks naming =version 2 bsize=4096 ascii-ci=0 ftype=1 log =internal log bsize=4096 blocks=855, version=2 = sectsz=512 sunit=0 blks, lazy-count=1 realtime =none extsz=4096 blocks=0, rtextents=0 ---- [NOTE] ==== In this example, we create an xfs filesystem with no special options. In a production environment, you should choose a filesystem type and options that are suitable for your application. ==== Mount the newly created filesystem, populate it with our web document, give it the same SELinux policy as the web document root, then unmount it (the cluster will handle mounting and unmounting it later): ---- [root@pcmk-1 ~]# mount /dev/drbd1 /mnt [root@pcmk-1 ~]# cat <<-END >/mnt/index.html My Test Site - DRBD END [root@pcmk-1 ~]# chcon -R --reference=/var/www/html /mnt [root@pcmk-1 ~]# umount /dev/drbd1 ---- == Configure the Cluster for the DRBD device == One handy feature `pcs` has is the ability to queue up several changes into a file and commit those changes all at once. To do this, start by populating the file with the current raw XML config from the CIB. ---- [root@pcmk-1 ~]# pcs cluster cib drbd_cfg ---- Using pcs's `-f` option, make changes to the configuration saved in the +drbd_cfg+ file. These changes will not be seen by the cluster until the +drbd_cfg+ file is pushed into the live cluster's CIB later. Here, we create a cluster resource for the DRBD device, and an additional _clone_ resource to allow the resource to run on both nodes at the same time. ---- [root@pcmk-1 ~]# pcs -f drbd_cfg resource create WebData ocf:linbit:drbd \ drbd_resource=wwwdata op monitor interval=60s [root@pcmk-1 ~]# pcs -f drbd_cfg resource master WebDataClone WebData \ master-max=1 master-node-max=1 clone-max=2 clone-node-max=1 \ notify=true [root@pcmk-1 ~]# pcs -f drbd_cfg resource show ClusterIP (ocf::heartbeat:IPaddr2): Started pcmk-1 WebSite (ocf::heartbeat:apache): Started pcmk-1 Master/Slave Set: WebDataClone [WebData] Stopped: [ pcmk-1 pcmk-2 ] ---- +.Note +[NOTE] +==== +In Fedora 29 and CentOS 8.0, 'master' resources have been renamed to +'promotable clone' resources and the `pcs` command has been changed +accordingly: +---- +[root@pcmk-1 ~]# pcs -f drbd_cfg resource promotable WebData \ + promoted-max=1 promoted-node-max=1 clone-max=2 clone-node-max=1 \ + notify=true +---- +The new command does not allow to set a custom name for the resulting +promotable resource. `Pcs` automatically creates a name for the resource in +the form of *pass:[resource_name]-clone*, that is +*WebData-clone* in this case. + +To avoid confusion whether the +pcs resource show+ command displays resources' +status or configuration, the command has been deprecated in Fedora 29 and +CentOS 8.0. Two new commands have been introduced for displaying resources' +status and configuration: `pcs resource status` and `pcs resource config`, +respectively. +==== + After you are satisfied with all the changes, you can commit them all at once by pushing the drbd_cfg file into the live CIB. ---- [root@pcmk-1 ~]# pcs cluster cib-push drbd_cfg --config CIB updated ---- Let's see what the cluster did with the new configuration: ---- [root@pcmk-1 ~]# pcs status Cluster name: mycluster Stack: corosync Current DC: pcmk-2 (version 1.1.18-11.el7_5.3-2b07d5c5a9) - partition with quorum Last updated: Mon Sep 10 17:58:07 2018 Last change: Mon Sep 10 17:57:53 2018 by root via cibadmin on pcmk-1 2 nodes configured 4 resources configured Online: [ pcmk-1 pcmk-2 ] Full list of resources: ClusterIP (ocf::heartbeat:IPaddr2): Started pcmk-1 WebSite (ocf::heartbeat:apache): Started pcmk-1 Master/Slave Set: WebDataClone [WebData] Masters: [ pcmk-1 ] Slaves: [ pcmk-2 ] Daemon Status: corosync: active/disabled pacemaker: active/disabled pcsd: active/enabled ---- We can see that *WebDataClone* (our DRBD device) is running as master (DRBD's primary role) on *pcmk-1* and slave (DRBD's secondary role) on *pcmk-2*. [IMPORTANT] ==== The resource agent should load the DRBD module when needed if it's not already loaded. If that does not happen, configure your operating system to load the module at boot time. For &DISTRO; &DISTRO_VERSION;, you would run this on both nodes: ---- # echo drbd >/etc/modules-load.d/drbd.conf ---- ==== == Configure the Cluster for the Filesystem == Now that we have a working DRBD device, we need to mount its filesystem. In addition to defining the filesystem, we also need to tell the cluster where it can be located (only on the DRBD Primary) and when it is allowed to start (after the Primary was promoted). We are going to take a shortcut when creating the resource this time. Instead of explicitly saying we want the *ocf:heartbeat:Filesystem* script, we are only going to ask for *Filesystem*. We can do this because we know there is only one resource script named *Filesystem* available to pacemaker, and that pcs is smart enough to fill in the *ocf:heartbeat:* portion for us correctly in the configuration. If there were multiple *Filesystem* scripts from different OCF providers, we would need to specify the exact one we wanted. Once again, we will queue our changes to a file and then push the new configuration to the cluster as the final step. ---- [root@pcmk-1 ~]# pcs cluster cib fs_cfg [root@pcmk-1 ~]# pcs -f fs_cfg resource create WebFS Filesystem \ device="/dev/drbd1" directory="/var/www/html" fstype="xfs" Assumed agent name 'ocf:heartbeat:Filesystem' (deduced from 'Filesystem') [root@pcmk-1 ~]# pcs -f fs_cfg constraint colocation add \ WebFS with WebDataClone INFINITY with-rsc-role=Master [root@pcmk-1 ~]# pcs -f fs_cfg constraint order \ promote WebDataClone then start WebFS Adding WebDataClone WebFS (kind: Mandatory) (Options: first-action=promote then-action=start) ---- We also need to tell the cluster that Apache needs to run on the same machine as the filesystem and that it must be active before Apache can start. ---- [root@pcmk-1 ~]# pcs -f fs_cfg constraint colocation add WebSite with WebFS INFINITY [root@pcmk-1 ~]# pcs -f fs_cfg constraint order WebFS then WebSite Adding WebFS WebSite (kind: Mandatory) (Options: first-action=start then-action=start) ---- Review the updated configuration. ---- [root@pcmk-1 ~]# pcs -f fs_cfg constraint Location Constraints: Resource: WebSite Enabled on: pcmk-1 (score:50) Ordering Constraints: start ClusterIP then start WebSite (kind:Mandatory) promote WebDataClone then start WebFS (kind:Mandatory) start WebFS then start WebSite (kind:Mandatory) Colocation Constraints: WebSite with ClusterIP (score:INFINITY) WebFS with WebDataClone (score:INFINITY) (with-rsc-role:Master) WebSite with WebFS (score:INFINITY) Ticket Constraints: [root@pcmk-1 ~]# pcs -f fs_cfg resource show ClusterIP (ocf::heartbeat:IPaddr2): Started pcmk-1 WebSite (ocf::heartbeat:apache): Started pcmk-1 Master/Slave Set: WebDataClone [WebData] Masters: [ pcmk-1 ] Slaves: [ pcmk-2 ] WebFS (ocf::heartbeat:Filesystem): Stopped ---- After reviewing the new configuration, upload it and watch the cluster put it into effect. ---- [root@pcmk-1 ~]# pcs cluster cib-push fs_cfg --config CIB updated [root@pcmk-1 ~]# pcs status Cluster name: mycluster Stack: corosync Current DC: pcmk-2 (version 1.1.18-11.el7_5.3-2b07d5c5a9) - partition with quorum Last updated: Mon Sep 10 18:02:24 2018 Last change: Mon Sep 10 18:02:14 2018 by root via cibadmin on pcmk-1 2 nodes configured 5 resources configured Online: [ pcmk-1 pcmk-2 ] Full list of resources: ClusterIP (ocf::heartbeat:IPaddr2): Started pcmk-1 WebSite (ocf::heartbeat:apache): Started pcmk-1 Master/Slave Set: WebDataClone [WebData] Masters: [ pcmk-1 ] Slaves: [ pcmk-2 ] WebFS (ocf::heartbeat:Filesystem): Started pcmk-1 Daemon Status: corosync: active/disabled pacemaker: active/disabled pcsd: active/enabled ---- == Test Cluster Failover == Previously, we used `pcs cluster stop pcmk-1` to stop all cluster services on *pcmk-1*, failing over the cluster resources, but there is another way to safely simulate node failure. We can put the node into _standby mode_. Nodes in this state continue to run corosync and pacemaker but are not allowed to run resources. Any resources found active there will be moved elsewhere. This feature can be particularly useful when performing system administration tasks such as updating packages used by cluster resources. Put the active node into standby mode, and observe the cluster move all the resources to the other node. The node's status will change to indicate that it can no longer host resources, and eventually all the resources will move. ---- [root@pcmk-1 ~]# pcs cluster standby pcmk-1 [root@pcmk-1 ~]# pcs status Cluster name: mycluster Stack: corosync Current DC: pcmk-2 (version 1.1.18-11.el7_5.3-2b07d5c5a9) - partition with quorum Last updated: Mon Sep 10 18:04:22 2018 Last change: Mon Sep 10 18:03:43 2018 by root via cibadmin on pcmk-1 2 nodes configured 5 resources configured Node pcmk-1: standby Online: [ pcmk-2 ] Full list of resources: ClusterIP (ocf::heartbeat:IPaddr2): Started pcmk-2 WebSite (ocf::heartbeat:apache): Started pcmk-2 Master/Slave Set: WebDataClone [WebData] Masters: [ pcmk-2 ] Stopped: [ pcmk-1 ] WebFS (ocf::heartbeat:Filesystem): Started pcmk-2 Daemon Status: corosync: active/disabled pacemaker: active/disabled pcsd: active/enabled ---- Once we've done everything we needed to on pcmk-1 (in this case nothing, we just wanted to see the resources move), we can allow the node to be a full cluster member again. ---- [root@pcmk-1 ~]# pcs cluster unstandby pcmk-1 [root@pcmk-1 ~]# pcs status Cluster name: mycluster Stack: corosync Current DC: pcmk-2 (version 1.1.18-11.el7_5.3-2b07d5c5a9) - partition with quorum Last updated: Mon Sep 10 18:05:22 2018 Last change: Mon Sep 10 18:05:21 2018 by root via cibadmin on pcmk-1 2 nodes configured 5 resources configured Online: [ pcmk-1 pcmk-2 ] Full list of resources: ClusterIP (ocf::heartbeat:IPaddr2): Started pcmk-2 WebSite (ocf::heartbeat:apache): Started pcmk-2 Master/Slave Set: WebDataClone [WebData] Masters: [ pcmk-2 ] Slaves: [ pcmk-1 ] WebFS (ocf::heartbeat:Filesystem): Started pcmk-2 Daemon Status: corosync: active/disabled pacemaker: active/disabled pcsd: active/enabled ---- Notice that *pcmk-1* is back to the *Online* state, and that the cluster resources stay where they are due to our resource stickiness settings configured earlier. + +.Note +[NOTE] +==== +Since Fedora 29 and CentOS 8.0, the commands for controlling standby mode are +`pcs node standby` and `pcs node unstandby`. +====