[libvirt] [PATCH v2 14/15] docs: convert kbase/locking-sanlock.html.in to RST
Daniel P. Berrangé
berrange at redhat.com
Fri Nov 22 14:47:01 UTC 2019
This is a semi-automated conversion. The first conversion is done using
"pandoc -f html -t rst". The result is then editted manually to apply
the desired heading markup, and fix a few things that pandoc gets wrong.
Signed-off-by: Daniel P. Berrangé <berrange at redhat.com>
---
docs/kbase/locking-sanlock.html.in | 247 -----------------------------
docs/kbase/locking-sanlock.rst | 193 ++++++++++++++++++++++
2 files changed, 193 insertions(+), 247 deletions(-)
delete mode 100644 docs/kbase/locking-sanlock.html.in
create mode 100644 docs/kbase/locking-sanlock.rst
diff --git a/docs/kbase/locking-sanlock.html.in b/docs/kbase/locking-sanlock.html.in
deleted file mode 100644
index 3ee9849e87..0000000000
--- a/docs/kbase/locking-sanlock.html.in
+++ /dev/null
@@ -1,247 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<!DOCTYPE html>
-<html xmlns="http://www.w3.org/1999/xhtml">
- <body>
- <h1>Virtual machine lock manager, sanlock plugin</h1>
-
- <ul id="toc"></ul>
-
- <p>
- This page describes use of the
- <a href="https://fedorahosted.org/sanlock/">sanlock</a>
- service as a <a href="locking.html">lock driver</a>
- plugin for virtual machine disk mutual exclusion.
- </p>
-
- <h2><a id="sanlock">Sanlock daemon setup</a></h2>
-
- <p>
- On many operating systems, the <strong>sanlock</strong> plugin
- is distributed in a sub-package which needs to be installed
- separately from the main libvirt RPM. On a Fedora/RHEL host
- this can be done with the <code>yum</code> command
- </p>
-
- <pre>
-$ su - root
-# yum install libvirt-lock-sanlock
- </pre>
-
- <p>
- The next step is to start the sanlock daemon. For maximum
- safety sanlock prefers to have a connection to a watchdog
- daemon. This will cause the entire host to be rebooted in
- the event that sanlock crashes / terminates abnormally.
- To start the watchdog daemon on a Fedora/RHEL host
- the following commands can be run:
- </p>
-
- <pre>
-$ su - root
-# chkconfig wdmd on
-# service wdmd start
- </pre>
-
- <p>
- Once the watchdog is running, sanlock can be started
- as follows
- </p>
-
- <pre>
-# chkconfig sanlock on
-# service sanlock start
- </pre>
-
- <p>
- <em>Note:</em> if you wish to avoid the use of the
- watchdog, add the following line to <code>/etc/sysconfig/sanlock</code>
- before starting it
- </p>
-
- <pre>
-SANLOCKOPTS="-w 0"
- </pre>
-
- <p>
- The sanlock daemon must be started on every single host
- that will be running virtual machines. So repeat these
- steps as necessary.
- </p>
-
- <h2><a id="sanlockplugin">libvirt sanlock plugin configuration</a></h2>
-
- <p>
- Once the sanlock daemon is running, the next step is to
- configure the libvirt sanlock plugin. There is a separate
- configuration file for each libvirt driver that is using
- sanlock. For QEMU, we will edit <code>/etc/libvirt/qemu-sanlock.conf</code>
- There is one mandatory parameter that needs to be set,
- the <code>host_id</code>. This is an integer between
- 1 and 2000, which must be set to a <strong>unique</strong>
- value on each host running virtual machines.
- </p>
-
- <pre>
-$ su - root
-# augtool -s set /files/etc/libvirt/qemu-sanlock.conf/host_id 1
- </pre>
-
- <p>
- Repeat this on every host, changing <strong>1</strong> to a
- unique value for the host.
- </p>
-
- <h2><a id="sanlockstorage">libvirt sanlock storage configuration</a></h2>
-
- <p>
- The sanlock plugin needs to create leases in a directory
- that is on a filesystem shared between all hosts running
- virtual machines. Obvious choices for this include NFS
- or GFS2. The libvirt sanlock plugin expects its lease
- directory be at <code>/var/lib/libvirt/sanlock</code>
- so update the host's <code>/etc/fstab</code> to mount
- a suitable shared/cluster filesystem at that location
- </p>
-
- <pre>
-$ su - root
-# echo "some.nfs.server:/export/sanlock /var/lib/libvirt/sanlock nfs hard,nointr 0 0" >> /etc/fstab
-# mount /var/lib/libvirt/sanlock
- </pre>
-
- <p>
- If your sanlock daemon happen to run under non-root
- privileges, you need to tell this to libvirt so it
- chowns created files correctly. This can be done by
- setting <code>user</code> and/or <code>group</code>
- variables in the configuration file. Accepted values
- range is specified in description to the same
- variables in <code>/etc/libvirt/qemu.conf</code>. For
- example:
- </p>
-
- <pre>
-augtool -s set /files/etc/libvirt/qemu-sanlock.conf/user sanlock
-augtool -s set /files/etc/libvirt/qemu-sanlock.conf/group sanlock
- </pre>
-
- <p>
- But remember, that if this is NFS share, you need a
- no_root_squash-ed one for chown (and chmod possibly)
- to succeed.
- </p>
-
- <p>
- In terms of storage requirements, if the filesystem
- uses 512 byte sectors, you need to allow for <code>1MB</code>
- of storage for each guest disk. So if you have a network
- with 20 virtualization hosts, each running 50 virtual
- machines and an average of 2 disks per guest, you will
- need <code>20*50*2 == 2000 MB</code> of storage for
- sanlock.
- </p>
-
-
- <p>
- On one of the hosts on the network is it wise to setup
- a cron job which runs the <code>virt-sanlock-cleanup</code>
- script periodically. This scripts deletes any lease
- files which are not currently in use by running virtual
- machines, freeing up disk space on the shared filesystem.
- Unless VM disks are very frequently created + deleted
- it should be sufficient to run the cleanup once a week.
- </p>
-
- <h2><a id="qemuconfig">QEMU/KVM driver configuration</a></h2>
-
- <p>
- The QEMU/KVM driver is fully integrated with the lock
- manager framework as of release <span>0.9.3</span>.
- The out of the box configuration, however, currently
- uses the <strong>nop</strong> lock manager plugin.
- To get protection for disks, it is thus necessary
- to reconfigure QEMU to activate the <strong>sanlock</strong>
- driver. This is achieved by editing the QEMU driver
- configuration file (<code>/etc/libvirt/qemu.conf</code>)
- and changing the <code>lock_manager</code> configuration
- tunable.
- </p>
-
- <pre>
-$ su - root
-# augtool -s set /files/etc/libvirt/qemu.conf/lock_manager sanlock
-# service libvirtd restart
- </pre>
-
- <p>
- If all went well, libvirtd will have talked to sanlock
- and created the basic lockspace. This can be checked
- by looking for existence of the following file
- </p>
-
- <pre>
-# ls /var/lib/libvirt/sanlock/
-__LIBVIRT__DISKS__
- </pre>
-
- <p>
- Every time you start a guest, additional lease files will appear
- in this directory, one for each virtual disk. The lease
- files are named based on the MD5 checksum of the fully qualified
- path of the virtual disk backing file. So if the guest is given
- a disk backed by <code>/var/lib/libvirt/images/demo.img</code>
- expect to see a lease <code>/var/lib/libvirt/sanlock/bfa0240911bc17753e0b473688822159</code>
- </p>
-
- <p>
- It should be obvious that for locking to work correctly, every
- host running virtual machines should have storage configured
- in the same way. The easiest way to do this is to use the libvirt
- storage pool capability to configure any NFS volumes, iSCSI targets,
- or SCSI HBAs used for guest storage. Simply replicate the same
- storage pool XML across every host. It is important that any
- storage pools exposing block devices are configured to create
- volume paths under <code>/dev/disks/by-path</code> to ensure
- stable paths across hosts. An example iSCSI configuration
- which ensures this is:
- </p>
-
- <pre>
-<pool type='iscsi'>
- <name>myiscsipool</name>
- <source>
- <host name='192.168.254.8'/>
- <device path='your-iscsi-target-iqn'/>
- </source>
- <target>
- <path>/dev/disk/by-path</path>
- </target>
-</pool>
- </pre>
-
- <h2><a id="domainconfig">Domain configuration</a></h2>
-
- <p>
- In case sanlock loses access to disk locks for some reason, it will
- kill all domains that lost their locks. This default behavior may
- be changed using
- <a href="formatdomain.html#elementsEvents">on_lockfailure
- element</a> in domain XML. When this element is present, sanlock
- will call <code>sanlock_helper</code> (provided by libvirt) with
- the specified action. This helper binary will connect to libvirtd
- and thus it may need to authenticate if libvirtd was configured to
- require that on the read-write UNIX socket. To provide the
- appropriate credentials to sanlock_helper, a
- <a href="auth.html#Auth_client_config">client authentication
- file</a> needs to contain something like the following:
- </p>
- <pre>
-[auth-libvirt-localhost]
-credentials=sanlock
-
-[credentials-sanlock]
-authname=login
-password=password
- </pre>
- </body>
-</html>
diff --git a/docs/kbase/locking-sanlock.rst b/docs/kbase/locking-sanlock.rst
new file mode 100644
index 0000000000..fece9df80e
--- /dev/null
+++ b/docs/kbase/locking-sanlock.rst
@@ -0,0 +1,193 @@
+============================================
+Virtual machine lock manager, sanlock plugin
+============================================
+
+.. contents::
+
+This page describes use of the
+`sanlock <https://fedorahosted.org/sanlock/>`__ service as a `lock
+driver <locking.html>`__ plugin for virtual machine disk mutual
+exclusion.
+
+Sanlock daemon setup
+====================
+
+On many operating systems, the **sanlock** plugin is distributed in a
+sub-package which needs to be installed separately from the main libvirt
+RPM. On a Fedora/RHEL host this can be done with the ``yum`` command
+
+::
+
+ $ su - root
+ # yum install libvirt-lock-sanlock
+
+The next step is to start the sanlock daemon. For maximum safety sanlock
+prefers to have a connection to a watchdog daemon. This will cause the
+entire host to be rebooted in the event that sanlock crashes /
+terminates abnormally. To start the watchdog daemon on a Fedora/RHEL
+host the following commands can be run:
+
+::
+
+ $ su - root
+ # chkconfig wdmd on
+ # service wdmd start
+
+Once the watchdog is running, sanlock can be started as follows
+
+::
+
+ # chkconfig sanlock on
+ # service sanlock start
+
+*Note:* if you wish to avoid the use of the watchdog, add the following
+line to ``/etc/sysconfig/sanlock`` before starting it
+
+::
+
+ SANLOCKOPTS="-w 0"
+
+The sanlock daemon must be started on every single host that will be
+running virtual machines. So repeat these steps as necessary.
+
+libvirt sanlock plugin configuration
+====================================
+
+Once the sanlock daemon is running, the next step is to configure the
+libvirt sanlock plugin. There is a separate configuration file for each
+libvirt driver that is using sanlock. For QEMU, we will edit
+``/etc/libvirt/qemu-sanlock.conf`` There is one mandatory parameter that
+needs to be set, the ``host_id``. This is an integer between 1 and 2000,
+which must be set to a **unique** value on each host running virtual
+machines.
+
+::
+
+ $ su - root
+ # augtool -s set /files/etc/libvirt/qemu-sanlock.conf/host_id 1
+
+Repeat this on every host, changing **1** to a unique value for the
+host.
+
+libvirt sanlock storage configuration
+=====================================
+
+The sanlock plugin needs to create leases in a directory that is on a
+filesystem shared between all hosts running virtual machines. Obvious
+choices for this include NFS or GFS2. The libvirt sanlock plugin expects
+its lease directory be at ``/var/lib/libvirt/sanlock`` so update the
+host's ``/etc/fstab`` to mount a suitable shared/cluster filesystem at
+that location
+
+::
+
+ $ su - root
+ # echo "some.nfs.server:/export/sanlock /var/lib/libvirt/sanlock nfs hard,nointr 0 0" >> /etc/fstab
+ # mount /var/lib/libvirt/sanlock
+
+If your sanlock daemon happen to run under non-root privileges, you need
+to tell this to libvirt so it chowns created files correctly. This can
+be done by setting ``user`` and/or ``group`` variables in the
+configuration file. Accepted values range is specified in description to
+the same variables in ``/etc/libvirt/qemu.conf``. For example:
+
+::
+
+ augtool -s set /files/etc/libvirt/qemu-sanlock.conf/user sanlock
+ augtool -s set /files/etc/libvirt/qemu-sanlock.conf/group sanlock
+
+But remember, that if this is NFS share, you need a no_root_squash-ed
+one for chown (and chmod possibly) to succeed.
+
+In terms of storage requirements, if the filesystem uses 512 byte
+sectors, you need to allow for ``1MB`` of storage for each guest disk.
+So if you have a network with 20 virtualization hosts, each running 50
+virtual machines and an average of 2 disks per guest, you will need
+``20*50*2 == 2000 MB`` of storage for sanlock.
+
+On one of the hosts on the network is it wise to setup a cron job which
+runs the ``virt-sanlock-cleanup`` script periodically. This scripts
+deletes any lease files which are not currently in use by running
+virtual machines, freeing up disk space on the shared filesystem. Unless
+VM disks are very frequently created + deleted it should be sufficient
+to run the cleanup once a week.
+
+QEMU/KVM driver configuration
+=============================
+
+The QEMU/KVM driver is fully integrated with the lock manager framework
+as of release 0.9.3. The out of the box configuration, however,
+currently uses the **nop** lock manager plugin. To get protection for
+disks, it is thus necessary to reconfigure QEMU to activate the
+**sanlock** driver. This is achieved by editing the QEMU driver
+configuration file (``/etc/libvirt/qemu.conf``) and changing the
+``lock_manager`` configuration tunable.
+
+::
+
+ $ su - root
+ # augtool -s set /files/etc/libvirt/qemu.conf/lock_manager sanlock
+ # service libvirtd restart
+
+If all went well, libvirtd will have talked to sanlock and created the
+basic lockspace. This can be checked by looking for existence of the
+following file
+
+::
+
+ # ls /var/lib/libvirt/sanlock/
+ __LIBVIRT__DISKS__
+
+Every time you start a guest, additional lease files will appear in this
+directory, one for each virtual disk. The lease files are named based on
+the MD5 checksum of the fully qualified path of the virtual disk backing
+file. So if the guest is given a disk backed by
+``/var/lib/libvirt/images/demo.img`` expect to see a lease
+``/var/lib/libvirt/sanlock/bfa0240911bc17753e0b473688822159``
+
+It should be obvious that for locking to work correctly, every host
+running virtual machines should have storage configured in the same way.
+The easiest way to do this is to use the libvirt storage pool capability
+to configure any NFS volumes, iSCSI targets, or SCSI HBAs used for guest
+storage. Simply replicate the same storage pool XML across every host.
+It is important that any storage pools exposing block devices are
+configured to create volume paths under ``/dev/disks/by-path`` to ensure
+stable paths across hosts. An example iSCSI configuration which ensures
+this is:
+
+::
+
+ <pool type='iscsi'>
+ <name>myiscsipool</name>
+ <source>
+ <host name='192.168.254.8'/>
+ <device path='your-iscsi-target-iqn'/>
+ </source>
+ <target>
+ <path>/dev/disk/by-path</path>
+ </target>
+ </pool>
+
+Domain configuration
+====================
+
+In case sanlock loses access to disk locks for some reason, it will kill
+all domains that lost their locks. This default behavior may be changed
+using `on_lockfailure element <formatdomain.html#elementsEvents>`__ in
+domain XML. When this element is present, sanlock will call
+``sanlock_helper`` (provided by libvirt) with the specified action. This
+helper binary will connect to libvirtd and thus it may need to
+authenticate if libvirtd was configured to require that on the
+read-write UNIX socket. To provide the appropriate credentials to
+sanlock_helper, a `client authentication
+file <auth.html#Auth_client_config>`__ needs to contain something like
+the following:
+
+::
+
+ [auth-libvirt-localhost]
+ credentials=sanlock
+
+ [credentials-sanlock]
+ authname=login
+ password=password
--
2.23.0
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