Site Management Workflow and Operations

Author
Michel Jouvin

Managing Users

At installation time, Aquilon is initialised with the Kerberos principal aquilon declared as the Aquilon administrator, meaning that it can use all the Aquilon commands. Normally, at a real site, you will have several users interacting with Aquilon and you want all of them to interact with its own Kerberos principal. This is done by adding new Aquilon users and defining their roles.

Define user role

To have a user account created automatically, have the user connect to the broker and run a read-only command, e.g. aq status. Once their Kerberos principal appears in the output of aq show_principal, they can be assigned a more specific role with aq permission. An unknown principal can also be created by passing --createuser to the aq permission command.

When a user first connect to Aquilon, its role is set to nobody. As a result, it is restricted to a few Aquilon commands, typically those who allow to display existing objects in the database. To administer objects, a user must have a role that allows to do it. It is possible to define as many role as needed and to specify explicitly what are the allowed commands for the role. The role aqdadmin is created at installation time and allows to use any Aquilon command.

Using Sandboxes

A sandbox is Git repository and a working directories that are associated with the Aquilon user who create it. This where the pan template development occurs.

As the Aquilon users typically don’t have access to the machine where the Aquilon broker runs, the sandbox area on the broker is generally put on a distributed file system, like NFS (see the installation guide for more details). The sandbox area must be writable by any machine used by Aquilon users.

To allow the user to access its sandbox files, it is necessary to provide the broker with a script that will define the appropriate owner, based on the UID defined for the user in the Aquilon database. See installation documentation for more details.

Define the Kerberos realm as trusted

To be able to add a sandbox, the Kerberos realm used to authenticate Aquilon users must be trusted. This is not the default when a realm is added. To declare a realm as trusted, use aq update_realm command.

The realm used is based on the Kerberos configuration that was done during Aquilon installation. Use klist command to get it, if you don’t know it.

Assuming that your real is called dailyplanet.com (it often matches your DNS domain), the command to use is:

aq update_realm --realm dailyplanet.com --trusted

Define Aquilon user UID

This section is only required if you are using using NFS for sandbox development but user accounts are not defined on the broker.

The broker needs to set the sandbox owner to user creating it. As the broker cannot retrieve the user UID from the user account when it is not defined on the broker host, it uses the user information defined in the Aquilon database to retrieve the UID to use.

To list existing users, use:

aq show_user --all

The Aquilon user defines the Linux UID, GID and home directory associated with the Aquilon user but in standard installation, only the UID is actually used. The Aquilon user name must match the Kerberos principal name used by the user to interact with the broker (typically its Linux userid) and the UID must match the actual UID of the user account.

If there is no entry yet for the user, one must be created with aq add_user. If the existing entry doesn’t have the right UID, use command aq update_user instead.

For example, to create an account for user johndoe, use the following commands:

# Retrieve the Linux `uid` and `gid` for this account
id johndoe
# Create the Aquilon account
aq add_user --user johndoe --uid uid_retrieved --gid gid_retrieved --home aquilon_account_dir

Sandbox creation

The command below will create the sandbox object and the Git repository associated in /var/quattor/templates/user/sandbox_name with user the Aquilon user matching the Kerberos principal used and sandbox_name the name of the sandbox create. The sandbox is a Git repository created as a clone of the template-king repository (template-king is the Git remote origin for the sandbox repository). The Aquilon user (in fact the UID associated with him) executing the command will own the sandbox working directory.

aq add_sandbox --sandbox site-init

Once the sandbox is created, it is necessary to associate the host we want to manage with the sandbox. In all the Aquilon commands requiring a --sandbox option (except the xxx_sandbox commands), the sandbox name is user/sandbox.

# The following command assumes that the Aquilon user has the same name as the current Linux user
aq manage --sandbox $USER/site-init --hostname 'testsrv.dailyplanet.com'

Note: if you want to remove the host from the sandbox, you need to use the same command with the option --domain instead of --sandbox to move it back to a domain. You can also move it to another sandbox.

You are now ready to produce some useful pan code to define the configuration of the host testsrv.dailyplanet.com.

Accessing Plenary Templates

Plenary templates are all the templates generated and owned by the broker. They cannot be edited: their content is modified by the Aquilon commands used to update the host configuration. For this reason, they cannot be accessed directly, for example in the sandbox. The content of these templates can be displayed with the aq cat command. Command options can be used to select the template to display: use aq cat --help to get the list of all the possible options. The main ones are:

  • --hostname xxx.dom.ain: object template for host xxx.dom.ain
  • --hostname xxx.dom.ain --data: host data template (archetype, hardware configuration, network configuration) for host xxx.dom.ain
  • --machine xxx: machine template for machine xxx
  • --cluster xxx: object template for cluster xxx
  • --cluster xxx --data: template describing members and location of cluster xxx
  • --cluster xxx --client: cluster configuration included in hosts who are members of cluster xxx
  • --personality xxx --archetype yyy [--personality_stage stage]: template describing personality xxx of archetype yyy (--archetype can be omitted if personality xxx exists only in one archetype). If --personality_stage is omitted, it defaults to current: specify it if you want to see the template for other stages (previous or next)
  • --service xxx: template describing the configuration common to all instances of service xxx
  • --service xxx --instance yyy: template describing instance yyy configuration of service xxx
  • --service xxx --server: template describing the common configuration all servers for service xxx
  • --service xxx --server --instance yyy: template describing the server configuration of instance yyy for service xxx

Note: the template library is also installed in the plenary template area and is not visible outside the broker. Currently, the aq cat command doesn’t allow to display the template library contents. If you need to check the content of a template in the template library, refer to the appropriate GitHub repository or download a private copy of the template library (outside of any sandbox) using the standard procedure.

Why to Use Domains

Domains are used to implement a stage development workflow where changes are tested first on a limited number of hosts, for example a dev domain, before going to production in a prod domain that contains all the site hosts, except those used for testing in the dev domain. You can implement as many stages as you want, for example a q/a or preprod domain, between dev and prod.

When validated in one domain, changes can be deployed into the domain representing the next stage with aq deploy.

Hosts can also be moved from one domain to another one with aq manage.

Adding Archetypes

Compilable archetypes

Compilable archetypes are used for hosts managed directly by Aquilon. They are the most common archetypes.

Non-compilable archetypes

Non-compilable archetypes are used to store the inventory for your hardware not managed by Aquilon. For example, you could create an archetype for all your IPMI hardware.

aq add_archetype --archetype 'ipmi' --nocompilable

Adding New Hardware Models

Arbitrary hardware components (disks, NIC, machine…) can be used to describe machines in the Aquilon database. But to be usable in host profiles, they have to be backed by Pan templates. This section requires what you need to do if you want to use hardware components with no template already existing in the template library. Once you have validated the new hardware templates, it is a good practice to request their addition to the template library so that other Aquilon sites can benefit from them.

Defining New Features

Adding a feature

We can now create a feature: this involves creating the feature object in the Aquilon database with the aq command and adding a pan template defining the feature. When creating a feature, it is necessary to define what action triggers its activation and deactivation. See aq help add feature for possible values.

aq add_feature --feature demo --type host --activation dispatch --deactivation reboot --grn test

Once the feature has been added, it is necessary to create a template config.pan that will define what the feature actually does. This template will first be added to the sandbox, /var/quattor/templates/user/aquilon, to test it. This template must reside at the path archetype/features/feature_name in the sandbox, with archetype the archetype the feature will belong to (in our example linux) and feature_name equal to the feature name (her demo). At this stage create a file with the following content:

unique template features/demo/config;

Once the template been created, it is necessary to commit it and push to the template-king Git repository which is defined as the origin of the template master repository for the domain, test here:

cd /var/quattor/domains/test
git add .
git commit -m 'Add features demon and rootpasswd'
git push

Binding features to personalities

A feature can be bound to one or more personalities. It means that all using these personalities will have the feature configured. The command to do it is aq bind_feature. For example to bind the feature demo created previously to the personality test, the command would be:

aq bind_feature --feature demo --personality test --archetype web_servers

Note: despite the command help mentions that features can also be bound to archetypes, it is highly recommended not to do it.

Personalities

Personalities are used to define the list of features that are configured on a host. Every host has one personality and only one but it is possible to change the personality of a host. Personalities are attached to one archetype (an archetype can be viewed as a group of possible personalities).

Personality configuration is staged. That means that when a personality is updated, the change is not visible to the hosts using it until it is promoted as the current version with the aq promote command. When a personality is created and when it is updated, its stage is defined to next (configuration that will be applied to the personality when the new configuration is promoted as the production (current) one. After aq promote the previously current personality configuration becomes previous.

Unlike features, personalities are entirely defined in the Aquilon database (there is no additional site template to create).

Defining the new personality configuration as current

Based on the feature example above, to use the updated personality configuration for the hosts having this personality, use the following command:

aq promote --personality test --archetype web_servers

Changing the host personality

To change the personality of an existing host, use aq reconfigure:

aq reconfigure --hostname your_host --personality new_personality [--archetype new_archetype]

--archetype is necessary only if the new personality is not attached to the same archetype.

Networks

How to define the routers for my networks?

When we declare our networks, Aquilon will assume a fixed IP (typically the first IP in the range) is the gateway in it. If this isn’t correct, you have to modify the configuration for the broker. Create a network_unknown section, and declare the default gateway offset.

[network_unknown]
default_gateway_offset=30
reserved_offsets=1,30,25
first_usable_offset=40

And finally we restart the broker:

systemctl restart aquilon-broker

If some of your networks don’t adhere to this convention, you’ll need to declare their routers in Aquilon. For instance, let’s suppose that the gateway in reporters network has offset 3:

aq add_router --ip '192.168.100.3' --fqdn 'router.reporters.metropolis.com'

If your network is an internal one (the default), some restrictions apply:

  • Routers must be part of the reserved_offsets list.
  • Router offsets must be below the first_usable_offset, which the broker uses when assigning IP addresses automatically.

If you need an external network, you have to create it with --network_environment external in its command line.

Services

An Aquilon service allows to define different endpoints for a given service based on the host location information (country, city, room, rack…) or the host network subnet. A host can be bound to the service and the appropriate instance will be selected by the Aquilon broker and passed to the host configuration in /system/services/servicename where servicename is the name of the service. The 2 main configuration properties accessible are:

  • servers: the endpoint FQDNs of the appropriate service instance, as a Pan list of string
  • server_ips: the endpoint IP addresses of the appropriate service instance, as a Pan list of string

Defining a service

Defining a service typically involves creating a service instance and mapping it to specific hosts, personalities or archetypes. When mapped to a personality or archetype, the service will be used for all nodes in this personality or archetype for which there is no explicit mapping.

To create the service dns (to define the DNS server to use), use the following command:

aq add service --service dns

Then create a service instance (the instance can have a different setting for –need_client_list`), defining its associated endpoint. The associated endpoint must be a host entry in the Aquilon database. If the endpoint is not managed by Aquilon, define it in a non-compilable archetype:

aq add service --service dns --instance metropolis1
aq bind server --service dns --instance metropolis1  --hostname ns.deilyplanet.com

Assigning hosts to a service instance

Once a service has been defined, it is necessary to define which hosts are configured to use it. This is done by marking the service as required for a given archetype or personality with the command aq add_required_service which means that all the hosts with this archetype of personality will have the service configured, using the appropriate instance for the host. For example, to define the dns service as required for the archetype web_servers, use:

aq add required service --service dns --archetype web_servers

Hosts are assigned to service instance using service maps. A service map define the criteria to use to select an instance. They are typically based on the geographical locations but it also possible to use network subnets. When using the location information, it is possible to define different instances for different parts of the location hierarchy. For example, it is possible to define an instance that will be used for a city with the exception of one building that will have its own service mapping. This is done with the command aq map_service. For example:

aq map service --service dns --instance metropolis1  --city metropolis
# Instance metropolis2 needs to be defined before
aq map service --service dns --instance metropolis2  --building hq

You need to run the command aq reconfigure for a host for the service configuration changes to be actually taken into account in host profile. Note that this command will fail if there is no service instance that can serve a host for which the service is required, i.e. if the service mapping has not been properly defined to handle the location or network of the host.

After running aq reconfigure for some hosts assigned to the service, aq show service should show a non-zero number for the service Client Count.

Checking if a host has been assigned to a service

To check if a node has been assigned to a service and to know which instance will be used, use the command aq show service --client clientname where clientname is the host name to check.

Unbinding a client from a service

To unbind a client from a service instance, it is necessary to remove the service requirement matching the host with the command aq del required service.

The mapping is actually removed at the next aq reconfigure for the host after modifying the service requirements.

Initial Installation

Initial installation of a node in Quattor is managed by the AII component that generally runs on a dedicated node. A site can use multiple AII servers, typically one per network subnet.

In Aquilon, the AII server that is used for a given host is defined by the Aquilon service bootserver service. To define it, follow the instructions above to create the service and configure it. In particular declare one or more instances of the service and map them to hosts, for example based on their locations.

Once the service is configured, the AII configuration for a host is generated by command when command aq pxeswitch is run. Use this command with the option --install to get the host installed at next boot and --status to inquire what will happen for the host at next boot (--localboot reset --install, defining that next boot must be done from local disk).

Note: it is possible to share the deployment (AII) server between SCDB (Quattor legacy configuration database) and Aquilon (or between several Aquilon brokers) but with Aquilon 1.12.62 and Quattor 18.6.0, it requires 2 fixes: https://github.com/quattor/aquilon/pull/114 and https://github.com/quattor/aii/pull/291.

Implementing Modifications in the Template Library

The template library provides the base templates for configuring the host operating system and some features, in particular for OpenStack cloud and for UMD grid middleware. It has been designed to highly configurable without any modification, using variables. The templates are developed by the Quattor community. They help to lower the management effort required at each site.

The template library is not intended to be modified directly by a site. This is the reason it is part of the plenary templates that are not visible to Aquilon users and that they are not versioned. See the dedicated section for more information on how to integrate the template library into Aquilon.

It may happen that some of the templates need to be enhanced or that a site develops a new feature that may be useful to other sites. In this case, it is recommended to create at the top level of the site templates a template-library directory. In this directory, create a sub-directory whose name is the template library version the modification apply to. This is the same directory structure as the one used in the plenary templates.

Then for each template that you need to modify or add, place it in the same directory as it would be in the template library: the site version will be used instead of the standard one, without any modification to the other templates.

When a new version of the template library is released, it is easy to compare the new templates with the local modifications to decide what still needs to be ported to the new version, using the same approach (a directory corresponding to the new version).

It is important to submit your modification upstream, using GitHub pull requests against the relevant repositories. Avoid submitting one big pull request with all your changes: prefer submitting one pull request per change set.

Implementing Peer-Review and Quality Assessment with Aquilon

Implementing a stage deployment workflow, Aquilon makes easy to validate changes through peer-review and a quality assessment process.

Peer-review is generally implemented when the changes are published from a sandbox. Since the template-king repository is a standard Git repository, you can set up a simple system just by adding an post-receive hook that sends an email to the peer-review team.

Quality assessment can be implemented in various ways. One common practice is to have a domain with a set of hosts representing the various services managed in Aquilon where changes are deployed after the initial validation (e.g. in domain dev) and before being moved to the production domain