mdadm resource¶
Use the mdadm resource to manage RAID devices in a Linux environment using the mdadm utility. The mdadm resource will create and assemble an array, but it will not create the config file that is used to persist the array upon reboot. If the config file is required, it must be done by specifying a template with the correct array layout, and then by using the mount resource to create a file systems table (fstab) entry.
Syntax¶
The mdadm resource has the following syntax:
mdadm 'name' do
bitmap String
chunk Integer # default value: 16
devices Array
exists true, false # default value: false
layout String
level Integer # default value: 1
metadata String # default value: 0.90
raid_device String # default value: 'name' unless specified
action Symbol # defaults to :create if not specified
end
where:
mdadm
is the resource.name
is the name given to the resource block.action
identifies which steps the chef-client will take to bring the node into the desired state.bitmap
,chunk
,devices
,exists
,layout
,level
,metadata
, andraid_device
are the properties available to this resource.
Actions¶
The mdadm resource has the following actions:
:assemble
- Assemble a previously created array into an active array.
:create
- Default. Create an array with per-device superblocks. If an array already exists (but does not match), update that array to match.
:nothing
- Define this resource block to do nothing until notified by another resource to take action. When this resource is notified, this resource block is either run immediately or it is queued up to be run at the end of the Chef Client run.
:stop
- Stop an active array.
Properties¶
The mdadm resource has the following properties:
bitmap
Ruby Type: String
The path to a file in which a write-intent bitmap is stored.
chunk
Ruby Type: Integer | Default Value:
16
The chunk size. This property should not be used for a RAID 1 mirrored pair (i.e. when the
level
property is set to1
).devices
Ruby Type: Array
The devices to be part of a RAID array.
exists
Ruby Type: true, false | Default Value:
false
Indicates whether the RAID array exists.
ignore_failure
Ruby Type: true, false | Default Value:
false
Continue running a recipe if a resource fails for any reason.
layout
Ruby Type: String
The RAID5 parity algorithm. Possible values:
left-asymmetric
(orla
),left-symmetric
(orls
),right-asymmetric
(orra
), orright-symmetric
(orrs
).level
Ruby Type: Integer | Default Value:
1
The RAID level.
metadata
Ruby Type: String | Default Value:
0.90
The superblock type for RAID metadata.
notifies
Ruby Type: Symbol, ‘Chef::Resource[String]’
A resource may notify another resource to take action when its state changes. Specify a
'resource[name]'
, the:action
that resource should take, and then the:timer
for that action. A resource may notify more than one resource; use anotifies
statement for each resource to be notified.A timer specifies the point during the Chef Client run at which a notification is run. The following timers are available:
:before
- Specifies that the action on a notified resource should be run before processing the resource block in which the notification is located.
:delayed
- Default. Specifies that a notification should be queued up, and then executed at the end of the Chef Client run.
:immediate
,:immediately
- Specifies that a notification should be run immediately, per resource notified.
The syntax for
notifies
is:notifies :action, 'resource[name]', :timer
raid_device
Ruby Type: String
The name of the RAID device. Default value: the
name
of the resource block. See “Syntax” section above for more information.retries
Ruby Type: Integer | Default Value:
0
The number of times to catch exceptions and retry the resource.
retry_delay
Ruby Type: Integer | Default Value:
2
The retry delay (in seconds).
subscribes
Ruby Type: Symbol, ‘Chef::Resource[String]’
A resource may listen to another resource, and then take action if the state of the resource being listened to changes. Specify a
'resource[name]'
, the:action
to be taken, and then the:timer
for that action.Note that
subscribes
does not apply the specified action to the resource that it listens to - for example:file '/etc/nginx/ssl/example.crt' do mode '0600' owner 'root' end service 'nginx' do subscribes :reload, 'file[/etc/nginx/ssl/example.crt]', :immediately end
In this case the
subscribes
property reloads thenginx
service whenever its certificate file, located under/etc/nginx/ssl/example.crt
, is updated.subscribes
does not make any changes to the certificate file itself, it merely listens for a change to the file, and executes the:reload
action for its resource (in this examplenginx
) when a change is detected.A timer specifies the point during the Chef Client run at which a notification is run. The following timers are available:
:before
- Specifies that the action on a notified resource should be run before processing the resource block in which the notification is located.
:delayed
- Default. Specifies that a notification should be queued up, and then executed at the end of the Chef Client run.
:immediate
,:immediately
- Specifies that a notification should be run immediately, per resource notified.
The syntax for
subscribes
is:subscribes :action, 'resource[name]', :timer
Examples¶
The following examples demonstrate various approaches for using resources in recipes. If you want to see examples of how Chef uses resources in recipes, take a closer look at the cookbooks that Chef authors and maintains: https://github.com/chef-cookbooks.
Create and assemble a RAID 0 array
The mdadm command can be used to create RAID arrays. For example, a RAID 0 array named /dev/md0
with 10 devices would have a command similar to the following:
$ mdadm --create /dev/md0 --level=0 --raid-devices=10 /dev/s01.../dev/s10
where /dev/s01 .. /dev/s10
represents 10 devices (01, 02, 03, and so on). This same command, when expressed as a recipe using the mdadm resource, would be similar to:
mdadm '/dev/md0' do
devices [ '/dev/s01', ... '/dev/s10' ]
level 0
action :create
end
(again, where /dev/s01 .. /dev/s10
represents devices /dev/s01, /dev/s02, /dev/s03, and so on).
Create and assemble a RAID 1 array
mdadm '/dev/md0' do
devices [ '/dev/sda', '/dev/sdb' ]
level 1
action [ :create, :assemble ]
end
Create and assemble a RAID 5 array
The mdadm command can be used to create RAID arrays. For example, a RAID 5 array named /dev/sd0
with 4, and a superblock type of 0.90
would be similar to:
mdadm '/dev/sd0' do
devices [ '/dev/s1', '/dev/s2', '/dev/s3', '/dev/s4' ]
level 5
metadata '0.90'
chunk 32
action :create
end