Puppet - Resource Abstraction Layer

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In Puppet, Resource Abstraction Layer (RAL) can be considered as the core conceptualized model on which the whole infrastructure and Puppet setup works. In RAL, each alphabet has its own significant meaning which is defined as follows.

Resource [R]

A resource can be considered as all the resources which are used to model any configuration in Puppet. They are basically in-built resources which are by default present in Puppet. They can be considered as a set of resources belonging to a pre-defined resource type. They are similar to OOP concept in any other programming language wherein the object is an instance of class. In Puppet, its resource is an instance of a resource type.

Abstraction [A]

Abstraction can be considered as a key feature where the resources are defined independently from the target OS. In other words, while writing any manifest file the user need not worry about the target machine or the OS, which is present on that particular machine. In abstraction, resources give enough information about what needs to exist on the Puppet agent.

Puppet will take care of all the functionalities or magic happening behind the scene. Regardless of the resources and OS, Puppet will take care of implementing the configuration on the target machine, wherein the user need not worry how Puppet does behind the scenes.

In abstraction, Puppet separates out the resources from its implementation. This platformspecific configuration exists from providers. We can use multiple subcommands along with its providers.

Layer [L]

It is possible that one defines an entire machine setup and configuration in terms of collection of resources, and it can be viewed and managed via Puppet’s CLI interface.

Example for User Resource Type

[root@puppetmaster ~]# puppet describe user --providers 
user 
==== 
Manage users.
This type is mostly built to manage systemusers, 
so it is lacking some features useful for managing normalusers. 
This resource type uses the prescribed native tools for 
creating groups and generally uses POSIX APIs for retrieving informationabout them.
It does not directly modify '/etc/passwd' or anything. 

- **comment** 
   A description of the user.  Generally the user's full name.  

- **ensure** 
   The basic state that the object should be in. 
   Valid values are 'present', 'absent', 'role'.  

- **expiry** 
   The expiry date for this user. 
   Must be provided in a zero-padded YYYY-MM-DD format --- e.g. 2010-02-19. 
   If you want to make sure the user account does never expire, 
   you can pass the special value 'absent'. 
   Valid values are 'absent'. 
   Values can match '/^\d{4}-\d{2}-\d{2}$/'. 
   Requires features manages_expiry.  

- **forcelocal** 
   Forces the management of local accounts when accounts are also 
   being managed by some other NSS 
   Valid values are 'true', 'false', 'yes', 'no'. 
   Requires features libuser.  

- **gid** 
   The user's primary group.  Can be specified numerically or by name. 
   This attribute is not supported on Windows systems; use the ‘groups’ 
   attribute instead. (On Windows, designating a primary group is only 
   meaningful for domain accounts, which Puppet does not currently manage.)  

- **groups** 
   The groups to which the user belongs. The primary group should 
   not be listed, and groups should be identified by name rather than by 
   GID. Multiple groups should be specified as an array.  

- **home** 
   The home directory of the user.  The directory must be created 
   separately and is not currently checked for existence.  

- **ia_load_module**
   The name of the I&A module to use to manage this user. 
   Requires features manages_aix_lam.  

- **iterations** 
   This is the number of iterations of a chained computation of the 
   password hash (http://en.wikipedia.org/wiki/PBKDF2).  
   This parameter is used in OS X. 
   This field is required for managing passwords on OS X >= 10.8.  

- **key_membership** 
   Whether specified key/value pairs should be considered the 
   **complete list** ('inclusive') or the **minimum list** ('minimum') of 
   the user's attributes. Defaults to 'minimum'. 
   Valid values are 'inclusive', 'minimum'.  

- **keys** 
   Specify user attributes in an array of key = value pairs. 
   Requires features manages_solaris_rbac.  

- **managehome** 
   Whether to manage the home directory when managing the user. 
   This will create the home directory when 'ensure => present', and 
   delete the home directory when ‘ensure => absent’. Defaults to ‘false’. 
   Valid values are ‘true’, ‘false’, ‘yes’, ‘no’.  

- **membership** 
   Whether specified groups should be considered the **complete list** 
   (‘inclusive’) or the **minimum list** (‘minimum’) of groups to which 
   the user belongs. Defaults to ‘minimum’. 
   Valid values are ‘inclusive’, ‘minimum’. 

- **name** 
   The user name. While naming limitations vary by operating system, 
   it is advisable to restrict names to the lowest common denominator.  

- **password** 
   The user's password, in whatever encrypted format the local system requires. 
   * Most modern Unix-like systems use salted SHA1 password hashes. You can use 
      Puppet's built-in ‘sha1’ function to generate a hash from a password. 
   * Mac OS X 10.5 and 10.6 also use salted SHA1 hashes. 
   * Mac OS X 10.7 (Lion) uses salted SHA512 hashes. 
   The Puppet Labs [stdlib][] module contains a ‘str2saltedsha512’ 
   function which can generate password hashes for Lion. 
   * Mac OS X 10.8 and higher use salted SHA512 PBKDF2 hashes. 
   When managing passwords on these systems the salt and iterations properties 
   need to be specified as well as the password. 
   [stdlib]: https://github.com/puppetlabs/puppetlabs-stdlib/ 
   Be sure to enclose any value that includes a dollar sign ($) in single 
   quotes (') to avoid accidental variable interpolation. 
   Requires features manages_passwords.  

- **password_max_age** 
   The maximum number of days a password may be used before it must be changed. 
Requires features manages_password_age.  

- **password_min_age** 
   The minimum number of days a password must be used before it may be changed. 
Requires features manages_password_age.  

- **profile_membership** 
   Whether specified roles should be treated as the **complete list** 
   (‘inclusive’) or the **minimum list** (‘minimum’) of roles 
   of which the user is a member. Defaults to ‘minimum’. 
   Valid values are ‘inclusive’, ‘minimum’. 

- **profiles** 
   The profiles the user has.  Multiple profiles should be 
   specified as an array. 
Requires features manages_solaris_rbac.  

- **project** 
   The name of the project associated with a user. 
   Requires features manages_solaris_rbac.  

- **purge_ssh_keys** 
   Purge ssh keys authorized for the user 
   if they are not managed via ssh_authorized_keys. 
   When true, looks for keys in .ssh/authorized_keys in the user's home directory. 
   Possible values are true, false, or an array of 
   paths to file to search for authorized keys. 
   If a path starts with ~ or %h, this token is replaced with the user's home directory. 
   Valid values are ‘true’, ‘false’.  

- **role_membership** 
   Whether specified roles should be considered the **complete list** 
   (‘inclusive’) or the **minimum list** (‘minimum’) of roles the user has. 
   Defaults to ‘minimum’. 
Valid values are ‘inclusive’, ‘minimum’.  

- **roles** 
   The roles the user has.  Multiple roles should be 
   specified as an array. 
Requires features manages_solaris_rbac.  

- **salt** 
   This is the 32 byte salt used to generate the PBKDF2 password used in 
   OS X. This field is required for managing passwords on OS X >= 10.8. 
   Requires features manages_password_salt. 

- **shell** 
   The user's login shell.  The shell must exist and be 
   executable. 
   This attribute cannot be managed on Windows systems. 
   Requires features manages_shell. 

- **system** 
   Whether the user is a system user, according to the OS's criteria; 
   on most platforms, a UID less than or equal to 500 indicates a system 
   user. Defaults to ‘false’. 
   Valid values are ‘true’, ‘false’, ‘yes’, ‘no’.  

- **uid** 
   The user ID; must be specified numerically. If no user ID is 
   specified when creating a new user, then one will be chosen 
   automatically. This will likely result in the same user having 
   different UIDs on different systems, which is not recommended. 
   This is especially noteworthy when managing the same user on both Darwin and 
   other platforms, since Puppet does UID generation on Darwin, but 
   the underlying tools do so on other platforms. 
   On Windows, this property is read-only and will return the user's 
   security identifier (SID).  

Providers 
--------- 

- **aix** 
   User management for AIX. 
   * Required binaries: '/bin/chpasswd', '/usr/bin/chuser', 
   '/usr/bin/mkuser', '/usr/sbin/lsgroup', '/usr/sbin/lsuser', 
   '/usr/sbin/rmuser'. 
   * Default for ‘operatingsystem’ == ‘aix’. 
   * Supported features: ‘manages_aix_lam’, ‘manages_expiry’, 
   ‘manages_homedir’, ‘manages_password_age’, ‘manages_passwords’, 
   ‘manages_shell’. 

- **directoryservice** 
   User management on OS X. 
   * Required binaries: ‘/usr/bin/dscacheutil’, ‘/usr/bin/dscl’, 
   ‘/usr/bin/dsimport’, ‘/usr/bin/plutil’, ‘/usr/bin/uuidgen’. 
   * Default for ‘operatingsystem’ == ‘darwin’. 
   * Supported features: ‘manages_password_salt’, ‘manages_passwords’, 
   ‘manages_shell’.

- **hpuxuseradd** 
   User management for HP-UX. This provider uses the undocumented ‘-F’ 
   switch to HP-UX's special ‘usermod’ binary to work around the fact that 
   its standard ‘usermod’ cannot make changes while the user is logged in. 
   * Required binaries: ‘/usr/sam/lbin/useradd.sam’, 
   ‘/usr/sam/lbin/userdel.sam’, ‘/usr/sam/lbin/usermod.sam’. 
   * Default for ‘operatingsystem’ == ‘hp-ux’. 
   * Supported features: ‘allows_duplicates’, ‘manages_homedir’, 
   ‘manages_passwords’.  

- **ldap** 
   User management via LDAP. 
   This provider requires that you have valid values for all of the 
   LDAP-related settings in ‘puppet.conf’, including ‘ldapbase’.
   You will almost definitely need settings for ‘ldapuser’ and ‘ldappassword’ in order 
   for your clients to write to LDAP. 
* Supported features: ‘manages_passwords’, ‘manages_shell’.  

- **pw** 
   User management via ‘pw’ on FreeBSD and DragonFly BSD. 
   * Required binaries: ‘pw’. 
   * Default for ‘operatingsystem’ == ‘freebsd, dragonfly’. 
   * Supported features: ‘allows_duplicates’, ‘manages_expiry’, 
   ‘manages_homedir’, ‘manages_passwords’, ‘manages_shell’. 

- **user_role_add** 
   User and role management on Solaris, via ‘useradd’ and ‘roleadd’. 
   * Required binaries: ‘passwd’, ‘roleadd’, ‘roledel’, ‘rolemod’, 
   ‘useradd’, ‘userdel’, ‘usermod’. 
   * Default for ‘osfamily’ == ‘solaris’. 
   * Supported features: ‘allows_duplicates’, ‘manages_homedir’, 
   ‘manages_password_age’, ‘manages_passwords’, ‘manages_solaris_rbac’.  

- **useradd** 
   User management via ‘useradd’ and its ilk.  Note that you will need to 
   install Ruby's shadow password library (often known as ‘ruby-libshadow’) 
   if you wish to manage user passwords. 
   * Required binaries: ‘chage’, ‘luseradd’, ‘useradd’, ‘userdel’, ‘usermod’. 
   * Supported features: ‘allows_duplicates’, ‘libuser’, ‘manages_expiry’, 
   ‘manages_homedir’, ‘manages_password_age’, ‘manages_passwords’, 
   ‘manages_shell’, ‘system_users’.  

- **windows_adsi** 
   Local user management for Windows. 
   * Default for 'operatingsystem' == 'windows'. 
   * Supported features: 'manages_homedir', 'manages_passwords'. 

Testing Resource

In Puppet, testing a resource directly indicates that one needs to first apply resources which one wants to use to configures a target node, so that the state of the machine changes accordingly.

For testing we are going to apply the resource locally. As we have a resource predefined above with user = vipin. One way of applying a resource is by CLI. This can be done by re-writing the complete resource into a single command and then passing it to a resource sub command.

puppet resource user vipin ensure = present uid = '505' 
shell = '/bin/bash' home = '/home/vipin'

Test the applied resource.

[root@puppetmaster ~]# cat /etc/passwd | grep "vipin" 
vipin:x:505:501::/home/vipin:/bin/bash 

The above output shows that the resource is applied to the system and we have a new user created with the name of Vipin. It is advisable that you test this on your own as all the above codes are tested and are working codes.