Ansible ships with a number of modules (called the ‘module library’) that can be executed directly on remote hosts or through Playbooks. Users can also write their own modules. These modules can control system resources, like services, packages, or files (anything really), or handle executing system commands.
Let’s review how we execute three different modules from the command line:
ansible webservers -m service -a "name=httpd state=running"
ansible webservers -m ping
ansible webservers -m command -a "/sbin/reboot -t now"
Each module supports taking arguments. Nearly all modules take key=value arguments, space delimited. Some modules take no arguments, and the command/shell modules simply take the string of the command you want to run.
From playbooks, Ansible modules are executed in a very similar way:
- name: reboot the servers
action: command /sbin/reboot -t now
All modules technically return JSON format data, though if you are using the command line or playbooks, you don’t really need to know much about that. If you’re writing your own module, you care, and this means you do not have to write modules in any particular language – you get to choose.
Most modules other than command are idempotent, meaning they will seek to avoid changes to the system unless a change needs to be made. When using Ansible playbooks, these modules can trigger ‘change events’. Unless otherwise noted, any given module does support change hooks.
Let’s see what’s available in the Ansible module library, out of the box:
Manages apt-packages (such as for Debian/Ubuntu).
| parameter | required | default | comments |
|---|---|---|---|
| name | no | A package name or package specifier with version, like foo or foo=1.0 | |
| state | no | present | ‘absent’, ‘present’, or ‘latest’. |
| update_cache | no | no | Run the equivalent of apt-get update before the operation. Can be run as part of the package installation or a seperate step |
| purge | no | no | Will forge purge of configuration files if state is set to ‘removed’. |
| default_release | no | Corresponds to the -t option for apt and sets pin priorities | |
| install_recommends | no | yes | Corresponds to the –no-install-recommends option for apt, default behavior works as apt’s default behavior, ‘no’ does not install recommended packages. Suggested packages are never installed. |
Example action from Ansible Playbooks:
apt pkg=foo update-cache=yes
apt pkg=foo state=removed
apt pkg=foo state=installed
apt pkg=foo=1.00 state=installed
apt pkg=nginx state=latest default-release=squeeze-backports update-cache=yes
apt pkg=openjdk-6-jdk state=latest install-recommends=no
(new in 0.5) Assembles a configuration file from fragments. Often a particular program will take a single configuration file and does not support a conf.d style structure where it is easy to build up the configuration from multiple sources. Assmeble will take a directory of files that have already been transferred to the system, and concatenate them together to produce a destination file. Files are assembled in string sorting order. Puppet calls this idea “fragments”.
| parameter | required | default | comments |
|---|---|---|---|
| src | yes | An already existing directory full of source files | |
| dest | yes | A file to create using the concatenation of all of the source files | |
| OTHERS | All arguments that the file module takes may also be used |
Example action from Ansible Playbooks:
assemble src=/etc/someapp/fragments dest=/etc/someapp/someapp.conf
(new in 0.5). Adds or removes an authorized key for a user from a remote host.
| parameter | required | default | comments |
|---|---|---|---|
| user | yes | Name of the user who should have access to the remote host | |
| key | yes | the SSH public key, as a string | |
| state | no | present | whether the given key should or should not be in the file |
Example action from Ansible Playbooks:
authorized_key user=charlie key="ssh-dss ASDF1234L+8BTwaRYr/rycsBF1D8e5pTxEsXHQs4iq+mZdyWqlW++L6pMiam1A8yweP+rKtgjK2httVS6GigVsuWWfOd7/sdWippefq74nppVUELHPKkaIOjJNN1zUHFoL/YMwAAAEBALnAsQN10TNGsRDe5arBsW8cTOjqLyYBcIqgPYTZW8zENErFxt7ij3fW3Jh/sCpnmy8rkS7FyK8ULX0PEy/2yDx8/5rXgMIICbRH/XaBy9Ud5bRBFVkEDu/r+rXP33wFPHjWjwvHAtfci1NRBAudQI/98DbcGQw5HmE89CjgZRo5ktkC5yu/8agEPocVjdHyZr7PaHfxZGUDGKtGRL2QzRYukCmWo1cZbMBHcI5FzImvTHS9/8B3SATjXMPgbfBuEeBwuBK5EjL+CtHY5bWs9kmYjmeo0KfUMH8hY4MAXDoKhQ7DhBPIrcjS5jPtoGxIREZjba67r6/P2XKXaCZH6Fc= charlie@example.org 2011-01-17"
The command module takes the command name followed by a list of arguments, space delimited.
If you want to run a command through the shell (say you are using ‘<’, ‘>’, ‘|’, etc), you actually want the ‘shell’ module instead. The ‘command’ module is much more secure as it’s not affected by the user’s environment.
The given command will be executed on all selected nodes. It will not be processed through the shell, so variables like “$HOME” and operations like “<”, “>”, “|”, and “&” will not work. As such, all paths to commands must be fully qualified.
This module does not support change hooks and returns the return code from the program as well as timing information about how long the command was running.
Example action from Ansible Playbooks:
command /sbin/shutdown -t now
If you only want to run a command if a certain file does not exist, you can do the following:
command /usr/bin/make_database.sh arg1 arg2 creates=/path/to/database
The creates= option will not be passed to the executable.
The copy module moves a file on the local box to remote locations. In addition to the options listed below, the arguments available to the file module can also be passed to the copy module.
| parameter | required | default | comments |
|---|---|---|---|
| src | yes | Local path to a file to copy to the remote server, can be absolute or relative. | |
| dest | yes | Remote absolute path where the file should end up | |
| OTHERS | All arguments the file module takes are also supported |
This module also returns md5sum and other information about the resultant file.
Example action from Ansible Playbooks:
copy src=/srv/myfiles/foo.conf dest=/etc/foo.conf owner=foo group=foo mode=0644
Runs the discovery program ‘facter’ on the remote system, returning JSON data that can be useful for inventory purposes.
Requires that ‘facter’ and ‘ruby-json’ be installed on the remote end.
This module is informative only - it takes no parameters & does not support change hooks, nor does it make any changes on the system. Playbooks do not actually use this module, they use the setup module behind the scenes.
This module works like ‘copy’, but in reverse. It is used for fetching files from remote machines and storing them locally in a file tree, organized by hostname.
| parameter | required | default | comments |
|---|---|---|---|
| src | yes | The file on the remote system to fetch. This needs to be a file, not a directory. Recursive fetching may be supported in a later release. | |
| dest | yes | A directory to save the file into. For example, if the ‘dest’ directory is ‘/foo’, a src file named ‘/tmp/bar’ on host ‘host.example.com’, would be saved into ‘/foo/host.example.com/tmp/bar’ |
Example:
fetch src=/var/log/messages dest=/home/logtree
Sets attributes of files, symlinks, and directories, or removes files/symlinks/directories. Many other modules support the same options as the file module – including ‘copy’, ‘template’, and ‘assmeble’.
| parameter | required | default | comments |
|---|---|---|---|
| dest | yes | defines the file being managed, unless when used with state=link, and then sets the destination to create a symbolic link to using ‘src’ | |
| state | file | values are ‘file’, ‘link’, ‘directory’, or ‘absent’. If directory, all immediate subdirectories will be created if they do not exist. If ‘file’, the file will NOT be created if it does not exist, see the ‘copy’ or ‘template’ module if you want that behavior. If ‘link’, the symbolic link will be created or changed. If absent, directories will be recursively deleted, and files or symlinks will be unlinked. | |
| mode | mode the file or directory shoudl be, such as 0644 as would be fed to chmod. English modes like ‘g+x’ are not yet supported | ||
| owner | name of the user that should own the file/directory, as would be fed to chown | ||
| group | name of the group that should own the file/directory, as would be fed to group | ||
| src | path of the file to link to (applies only to state=link) | ||
| seuser | user part of SELinux file context. Will default to system policy, if applicable. If set to ‘_default’, it will use the ‘user’ portion of the the policy if available | ||
| serole | role part of SELinux file context, ‘_default’ feature works as above. | ||
| setype | type part of SELinux file context, ‘_default’ feature works as above | ||
| selevel | s0 | level part of the SELinux file context. This is the MLS/MCS attribute, sometimes known as the ‘range’. ‘_default’ feature works as above | |
| context | accepts only ‘default’ as a value. This will restore a file’s selinux context in the policy. Does nothing if no default is available. |
Example action from Ansible Playbooks:
file path=/etc/foo.conf owner=foo group=foo mode=0644
file path=/some/path owner=foo group=foo state=directory
file path=/path/to/delete state=absent
file src=/file/to/link/to dest=/path/to/symlink owner=foo group=foo state=link
file path=/some/path state=directory setype=httpd_sys_content_t
file path=/some/path state=directory context=default
Deploys software (or files) from git checkouts.
| parameter | required | default | comments |
|---|---|---|---|
| repo | yes | git, ssh, or http protocol address of the git repo | |
| dest | yes | absolute path of where the repo should be checked out to | |
| version | what version to check out – either the git SHA, the literal string ‘HEAD’, branch name, or a tag name. | ||
| remote | origin | name of the remote branch |
Example action from Ansible Playbooks:
git repo=git://foosball.example.org/path/to/repo.git dest=/srv/checkout version=release-0.22
Adds or removes groups.
| parameter | required | default | comments |
|---|---|---|---|
| name | yes | name of the group | |
| gid | optional git to set for the group | ||
| state | present | ‘absent’ or ‘present’ | |
| system | no | if ‘yes’, indicates that the group being created is a system group. |
To control members of the group, see the users resource.
Example action from Ansible Playbooks:
group name=somegroup state=present
Similar to the facter module, this returns JSON inventory data. Ohai data is a bit more verbose and nested than facter.
Requires that ‘ohai’ be installed on the remote end.
This module is information only - it takes no parameters & does not support change hooks, nor does it make any changes on the system.
Playbooks should not call the ohai module, playbooks call the setup module behind the scenes instead.
A trivial test module, this module always returns the integer 1 on successful contact.
This module does not support change hooks and is informative only - it takes no parameters & does not support change hooks, nor does it make any changes on the system.
Add or remove PostgreSQL databases from a remote host.
The default authentication assumes that you are either logging in as or sudo’ing to the postgres account on the host.
This module uses psycopg2, a Python PostgreSQL database adapter. You must ensure that psycopg2 is installed on the host before using this module. If the remote host is the PostgreSQL server (which is the default case), then PostgreSQL must also be installed on the remote host. For Ubuntu-based systems, install the postgresql, libpq-dev, and python-psycopg2 packages on the remote host before using this module.
| parameter | required | default | comments |
|---|---|---|---|
| db | yes | name of the database to add or remove | |
| login_user | no | postgres | user (role) used to authenticate with PostgreSQL |
| login_password | no | password used to authenticate with PostgreSQL | |
| login_host | no | host running PostgreSQL. Default (blank) implies localhost | |
| state | present | ‘absent’ or ‘present’ |
Example action from Ansible Playbooks:
postgresql_db db=acme
Add or remove PostgreSQL users (roles) from a remote host, and grant the users access to an existing database.
The default authentication assumes that you are either logging in as or sudo’ing to the postgres account on the host.
This module uses psycopg2, a Python PostgreSQL database adapter. You must ensure that psycopg2 is installed on the host before using this module. If the remote host is the PostgreSQL server (which is the default case), then PostgreSQL must also be installed on the remote host. For Ubuntu-based systems, install the postgresql, libpq-dev, and python-psycopg2 packages on the remote host before using this module.
| parameter | required | default | comments |
|---|---|---|---|
| user | yes | name of the user (role) to add or remove | |
| password | yes | set the user’s password | |
| db | yes | name of an existing database to grant user access to | |
| login_user | no | postgres | user (role) used to authenticate with PostgreSQL |
| login_password | no | password used to authenticate with PostgreSQL | |
| login_host | no | host running PostgreSQL. Default (blank) implies localhost | |
| state | present | ‘absent’ or ‘present’ |
Example action from Ansible Playbooks:
postgresql_user db=acme user=django password=ceec4eif7ya
Executes a low-down and dirty SSH command, not going through the module subsystem. This module is new in Ansible 0.4.
This is useful and should only be done in two cases. The first case is installing python-simplejson on older (python 2.4 and before) hosts that need it as a dependency to run modules, since nearly all core modules require it. Another is speaking to any devices such as routers that do not have any Python installed. In any other case, using the ‘shell’ or ‘command’ module is much more appropriate.
Arguments given to ‘raw’ are run directly through the configured remote shell and only output is returned. There is no error detection or change handler support for this module.
Example from /usr/bin/ansible to bootstrap a legacy python 2.4 host:
ansible newhost.example.com raw -a "yum install python-simplejson"
Controls services on remote machines.
| parameter | required | default | comments |
|---|---|---|---|
| name | yes | name of the service | |
| state | no | started | ‘started’, ‘stopped’, ‘reloaded’, or ‘restarted’. Started/stopped are idempotent actions that will not run commands unless neccessary. ‘restarted’ will always bounce the service, ‘reloaded’ will always reload. |
| enabled | no | Whether the service should start on boot. Either ‘yes’ or ‘no’. | |
| list | no | when used as ‘list=status’, returns the status of the service along with other results. Primarily useful for /usr/bin/ansible or playbooks with –verbose. |
Example action from Ansible Playbooks:
service name=httpd state=started
service name=httpd state=stopped
service name=httpd state=restarted
service name=httpd state=reloaded
This module is automatically called by playbooks to gather useful variables about remote hosts that can be used in playbooks. It can also be executed directly by /usr/bin/ansible to check what variables are available to a host.
Ansible provides many ‘facts’ about the system, automatically.
Some of the variables that are supplied are listed below. These in particular are from a VMWare Fusion 4 VM running CentOS 6.2:
"ansible_architecture": "x86_64",
"ansible_distribution": "CentOS",
"ansible_distribution_release": "Final",
"ansible_distribution_version": "6.2",
"ansible_eth0": {
"ipv4": {
"address": "REDACTED",
"netmask": "255.255.255.0"
},
"ipv6": [
{
"address": "REDACTED",
"prefix": "64",
"scope": "link"
}
],
"macaddress": "REDACTED"
},
"ansible_form_factor": "Other",
"ansible_fqdn": "localhost.localdomain",
"ansible_hostname": "localhost",
"ansible_interfaces": [
"lo",
"eth0"
],
"ansible_kernel": "2.6.32-220.2.1.el6.x86_64",
"ansible_lo": {
"ipv4": {
"address": "127.0.0.1",
"netmask": "255.0.0.0"
},
"ipv6": [
{
"address": "::1",
"prefix": "128",
"scope": "host"
}
],
"ansible_machine": "x86_64",
"ansible_memfree_mb": 89,
"ansible_memtotal_mb": 993,
"ansible_processor": [
"Intel(R) Core(TM) i7-2677M CPU @ 1.80GHz"
],
"ansible_processor_cores": "NA",
"ansible_processor_count": 1,
"ansible_product_name": "VMware Virtual Platform",
"ansible_product_serial": "REDACTED",
"ansible_product_uuid": "REDACTED",
"ansible_product_version": "None",
"ansible_python_version": "2.6.6",
"ansible_product_version": "None",
"ansible_python_version": "2.6.6",
"ansible_ssh_host_key_dsa_public": REDACTED",
"ansible_ssh_host_key_rsa_public": "REDACTED",
"ansible_swapfree_mb": 1822,
"ansible_swaptotal_mb": 2015,
"ansible_system": "Linux",
"ansible_system_vendor": "VMware, Inc.",
"ansible_virtualization_role": "None",
"ansible_virtualization_type": "None",
More ansible facts will be added with successive releases.
If facter or ohai are installed, variables from these programs will also be snapshotted into the JSON file for usage in templating. These variables are prefixed with facter_ and ohai_ so it’s easy to tell their source.
All variables are bubbled up to the caller. Using the ansible facts and choosing to not install facter and ohai means you can avoid ruby-dependencies on your remote systems.
Example action from /usr/bin/ansible:
ansible testserver -m setup
The shell module takes the command name followed by a list of arguments, space delimited. It is almost exactly like the command module but runs the command through the user’s configured shell on the remote node.
The given command will be executed on all selected nodes.
If you want to execute a command securely and predicably, it may be better to use the ‘command’ module instead. Best practices when writing playbooks will follow the trend of using ‘command’ unless ‘shell’ is explicitly required. When running ad-hoc commands, use your best judgement.
This module does not support change hooks and returns the return code from the program as well as timing information about how long the command was running.
Example action from a playbook:
shell somescript.sh >> somelog.txt
Templates a file out to a remote server.
| parameter | required | default | comments |
|---|---|---|---|
| src | yes | Path of a Jinja2 formatted template on the local server. This can be a relative or absolute path. | |
| dest | yes | Location to render the template on the remote server | |
| OTHERS | This module also supports all of the arguments to the file module |
Example action from a playbook:
template src=/srv/mytemplates/foo.j2 dest=/etc/foo.conf owner=foo group=foo mode=0644
Creates user accounts, manipulates existing user accounts, and removes user accounts.
| parameter | required | default | comments |
|---|---|---|---|
| name | yes | name of the user to create, remove, or edit | |
| comment | optionally sets the description of the user | ||
| uid | optionally sets the uid of the user | ||
| group | optionally sets the user’s primary group (takes a group name) | ||
| groups | puts the user in this comma-delimited list of groups | ||
| append | no | if ‘yes’, will only add groups, not set them to just the list in ‘groups’ | |
| shell | optionally set the user’s shell | ||
| createhome | yes | unless ‘no’, a home directory will be made for the user | |
| home | sets where the user’s homedir should be, if not the default | ||
| password | optionally set the user’s password to this crypted value. See the user’s example in the github examples directory for what this looks like in a playbook | ||
| state | present | when ‘absent’, removes the user. | |
| system | no | only when initially creating, setting this to ‘yes’ makes the user a system account. This setting cannot be changed on existing users. | |
| force | no | when used with state=absent, behavior is as with userdel –force | |
| remove | no | when used with state=remove, behavior is as with userdel –remove |
Example action from Ansible Playbooks:
user name=mdehaan comment=awesome passwd=awWxVV.JvmdHw createhome=yes
user name=mdehaan groups=wheel,skynet
user name=mdehaan state=absent force=yes
Manages virtual machines supported by libvirt. Requires that libvirt be installed on the managed machine.
| parameter | required | default | comments |
|---|---|---|---|
| name | yes | name of the guest VM being managed | |
| state | ‘running’, ‘shutdown’, ‘destroyed’, or ‘undefined’. Note that there may be some lag for state requests like ‘shutdown’ since these refer only to VM states. After starting a guest, it may not be immediately accessible. | ||
| command | in addition to state management, various non-idempotent commands are available. See examples below. |
Example action from Ansible Playbooks:
virt guest=alpha state=running
virt guest=alpha state=shutdown
virt guest=alpha state=destroyed
virt guest=alpha state=undefined
Example guest management commands from /usr/bin/ansible:
ansible host -m virt -a "guest=foo command=status"
ansible host -m virt -a "guest=foo command=pause"
ansible host -m virt -a "guest=foo command=unpause"
ansible host -m virt -a "guest=foo command=get_xml"
ansible host -m virt -a "guest=foo command=autostart"
Example host (hypervisor) management commands from /usr/bin/ansible:
ansible host -m virt -a "command=freemem"
ansible host -m virt -a "command=list_vms"
ansible host -m virt -a "command=info"
ansible host -m virt -a "command=nodeinfo"
ansible host -m virt -a "command=virttype"
Will install, upgrade, remove, and list packages with the yum package manager.
| parameter | required | default | comments |
|---|---|---|---|
| name | yes | package name, or package specifier with version, like ‘name-1.0’ | |
| state | present | ‘present’, ‘latest’, or ‘absent’. | |
| list | various non-idempotent commands for usage with /usr/bin/ansible and not playbooks. See examples below. |
Example action from Ansible Playbooks:
yum name=httpd state=latest
yum name=httpd state=removed
yum name=httpd state=installed
See Module Development.
See also