[libvirt] [PATCH v2 13/15] docs: convert kbase/locking-lockd.html.in to RST
Daniel P. Berrangé
berrange at redhat.com
Fri Nov 22 14:47:00 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-lockd.html.in | 160 -------------------------------
docs/kbase/locking-lockd.rst | 121 +++++++++++++++++++++++
2 files changed, 121 insertions(+), 160 deletions(-)
delete mode 100644 docs/kbase/locking-lockd.html.in
create mode 100644 docs/kbase/locking-lockd.rst
diff --git a/docs/kbase/locking-lockd.html.in b/docs/kbase/locking-lockd.html.in
deleted file mode 100644
index 855404ac97..0000000000
--- a/docs/kbase/locking-lockd.html.in
+++ /dev/null
@@ -1,160 +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, virtlockd plugin</h1>
-
- <ul id="toc"></ul>
-
- <p>
- This page describes use of the <code>virtlockd</code>
- service as a <a href="locking.html">lock driver</a>
- plugin for virtual machine disk mutual exclusion.
- </p>
-
- <h2><a id="background">virtlockd background</a></h2>
-
- <p>
- The virtlockd daemon is a single purpose binary which
- focuses exclusively on the task of acquiring and holding
- locks on behalf of running virtual machines. It is
- designed to offer a low overhead, portable locking
- scheme can be used out of the box on virtualization
- hosts with minimal configuration overheads. It makes
- use of the POSIX fcntl advisory locking capability
- to hold locks, which is supported by the majority of
- commonly used filesystems.
- </p>
-
- <h2><a id="sanlock">virtlockd daemon setup</a></h2>
-
- <p>
- In most OS, the virtlockd daemon itself will not require
- any upfront configuration work. It is installed by default
- when libvirtd is present, and a systemd socket unit is
- registered such that the daemon will be automatically
- started when first required. With OS that predate systemd
- though, it will be necessary to start it at boot time,
- prior to libvirtd being started. On RHEL/Fedora distros,
- this can be achieved as follows
- </p>
-
- <pre>
-# chkconfig virtlockd on
-# service virtlockd start
- </pre>
-
- <p>
- The above instructions apply to the instance of virtlockd
- that runs privileged, and is used by the libvirtd daemon
- that runs privileged. If running libvirtd as an unprivileged
- user, it will always automatically spawn an instance of
- the virtlockd daemon unprivileged too. This requires no
- setup at all.
- </p>
-
- <h2><a id="lockdplugin">libvirt lockd plugin configuration</a></h2>
-
- <p>
- Once the virtlockd daemon is running, or setup to autostart,
- the next step is to configure the libvirt lockd plugin.
- There is a separate configuration file for each libvirt
- driver that is using virtlockd. For QEMU, we will edit
- <code>/etc/libvirt/qemu-lockd.conf</code>
- </p>
-
- <p>
- The default behaviour of the lockd plugin is to acquire locks
- directly on the virtual disk images associated with the guest
- <disk> elements. This ensures it can run out of the box
- with no configuration, providing locking for disk images on
- shared filesystems such as NFS. It does not provide any cross
- host protection for storage that is backed by block devices,
- since locks acquired on device nodes in /dev only apply within
- the host. It may also be the case that the filesystem holding
- the disk images is not capable of supporting fcntl locks.
- </p>
-
- <p>
- To address these problems it is possible to tell lockd to
- acquire locks on an indirect file. Essentially lockd will
- calculate the SHA256 checksum of the fully qualified path,
- and create a zero length file in a given directory whose
- filename is the checksum. It will then acquire a lock on
- that file. Assuming the block devices assigned to the guest
- are using stable paths (eg /dev/disk/by-path/XXXXXXX) then
- this will allow for locks to apply across hosts. This
- feature can be enabled by setting a configuration setting
- that specifies the directory in which to create the lock
- files. The directory referred to should of course be
- placed on a shared filesystem (eg NFS) that is accessible
- to all hosts which can see the shared block devices.
- </p>
-
- <pre>
-$ su - root
-# augtool -s set \
- /files/etc/libvirt/qemu-lockd.conf/file_lockspace_dir \
- "/var/lib/libvirt/lockd/files"
- </pre>
-
- <p>
- If the guests are using either LVM and SCSI block devices
- for their virtual disks, there is a unique identifier
- associated with each device. It is possible to tell lockd
- to use this UUID as the basis for acquiring locks, rather
- than the SHA256 sum of the filename. The benefit of this
- is that the locking protection will work even if the file
- paths to the given block device are different on each
- host.
- </p>
-
- <pre>
-$ su - root
-# augtool -s set \
- /files/etc/libvirt/qemu-lockd.conf/scsi_lockspace_dir \
- "/var/lib/libvirt/lockd/scsi"
-# augtool -s set \
- /files/etc/libvirt/qemu-lockd.conf/lvm_lockspace_dir \
- "/var/lib/libvirt/lockd/lvm"
- </pre>
-
- <p>
- It is important to remember that the changes made to the
- <code>/etc/libvirt/qemu-lockd.conf</code> file must be
- propagated to all hosts before any virtual machines are
- launched on them. This ensures that all hosts are using
- the same locking mechanism
- </p>
-
- <h2><a id="qemuconfig">QEMU/KVM driver configuration</a></h2>
-
- <p>
- The QEMU driver is capable of using the virtlockd plugin
- since the release <span>1.0.2</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>lockd</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 lockd
-# service libvirtd restart
- </pre>
-
- <p>
- Every time you start a guest, the virtlockd daemon will acquire
- locks on the disk files directly, or in one of the configured
- lookaside directories based on SHA256 sum. To check that locks
- are being acquired as expected, the <code>lslocks</code> tool
- can be run.
- </p>
-
- </body>
-</html>
diff --git a/docs/kbase/locking-lockd.rst b/docs/kbase/locking-lockd.rst
new file mode 100644
index 0000000000..70e742b77c
--- /dev/null
+++ b/docs/kbase/locking-lockd.rst
@@ -0,0 +1,121 @@
+==============================================
+Virtual machine lock manager, virtlockd plugin
+==============================================
+
+.. contents::
+
+This page describes use of the ``virtlockd`` service as a `lock
+driver <locking.html>`__ plugin for virtual machine disk mutual
+exclusion.
+
+virtlockd background
+====================
+
+The virtlockd daemon is a single purpose binary which focuses
+exclusively on the task of acquiring and holding locks on behalf of
+running virtual machines. It is designed to offer a low overhead,
+portable locking scheme can be used out of the box on virtualization
+hosts with minimal configuration overheads. It makes use of the POSIX
+fcntl advisory locking capability to hold locks, which is supported by
+the majority of commonly used filesystems.
+
+virtlockd daemon setup
+======================
+
+In most OS, the virtlockd daemon itself will not require any upfront
+configuration work. It is installed by default when libvirtd is present,
+and a systemd socket unit is registered such that the daemon will be
+automatically started when first required. With OS that predate systemd
+though, it will be necessary to start it at boot time, prior to libvirtd
+being started. On RHEL/Fedora distros, this can be achieved as follows
+
+::
+
+ # chkconfig virtlockd on
+ # service virtlockd start
+
+The above instructions apply to the instance of virtlockd that runs
+privileged, and is used by the libvirtd daemon that runs privileged. If
+running libvirtd as an unprivileged user, it will always automatically
+spawn an instance of the virtlockd daemon unprivileged too. This
+requires no setup at all.
+
+libvirt lockd plugin configuration
+==================================
+
+Once the virtlockd daemon is running, or setup to autostart, the next
+step is to configure the libvirt lockd plugin. There is a separate
+configuration file for each libvirt driver that is using virtlockd. For
+QEMU, we will edit ``/etc/libvirt/qemu-lockd.conf``
+
+The default behaviour of the lockd plugin is to acquire locks directly
+on the virtual disk images associated with the guest <disk> elements.
+This ensures it can run out of the box with no configuration, providing
+locking for disk images on shared filesystems such as NFS. It does not
+provide any cross host protection for storage that is backed by block
+devices, since locks acquired on device nodes in /dev only apply within
+the host. It may also be the case that the filesystem holding the disk
+images is not capable of supporting fcntl locks.
+
+To address these problems it is possible to tell lockd to acquire locks
+on an indirect file. Essentially lockd will calculate the SHA256
+checksum of the fully qualified path, and create a zero length file in a
+given directory whose filename is the checksum. It will then acquire a
+lock on that file. Assuming the block devices assigned to the guest are
+using stable paths (eg /dev/disk/by-path/XXXXXXX) then this will allow
+for locks to apply across hosts. This feature can be enabled by setting
+a configuration setting that specifies the directory in which to create
+the lock files. The directory referred to should of course be placed on
+a shared filesystem (eg NFS) that is accessible to all hosts which can
+see the shared block devices.
+
+::
+
+ $ su - root
+ # augtool -s set \
+ /files/etc/libvirt/qemu-lockd.conf/file_lockspace_dir \
+ "/var/lib/libvirt/lockd/files"
+
+If the guests are using either LVM and SCSI block devices for their
+virtual disks, there is a unique identifier associated with each device.
+It is possible to tell lockd to use this UUID as the basis for acquiring
+locks, rather than the SHA256 sum of the filename. The benefit of this
+is that the locking protection will work even if the file paths to the
+given block device are different on each host.
+
+::
+
+ $ su - root
+ # augtool -s set \
+ /files/etc/libvirt/qemu-lockd.conf/scsi_lockspace_dir \
+ "/var/lib/libvirt/lockd/scsi"
+ # augtool -s set \
+ /files/etc/libvirt/qemu-lockd.conf/lvm_lockspace_dir \
+ "/var/lib/libvirt/lockd/lvm"
+
+It is important to remember that the changes made to the
+``/etc/libvirt/qemu-lockd.conf`` file must be propagated to all hosts
+before any virtual machines are launched on them. This ensures that all
+hosts are using the same locking mechanism
+
+QEMU/KVM driver configuration
+=============================
+
+The QEMU driver is capable of using the virtlockd plugin since the
+release 1.0.2. 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 **lockd** 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 lockd
+ # service libvirtd restart
+
+Every time you start a guest, the virtlockd daemon will acquire locks on
+the disk files directly, or in one of the configured lookaside
+directories based on SHA256 sum. To check that locks are being acquired
+as expected, the ``lslocks`` tool can be run.
--
2.23.0
More information about the libvir-list
mailing list