TERM environment variable not set.

Sometimes* when you are entering a docker container with docker exec -ti <container-name> bash the basic bash commands like top, less, more, clear or vim don’t work.

All you get is error messages complaining that the terminal does not work or the TERM environment variable is not set:

clear, top

TERM environment variable not set.

nano

Error opening terminal: unknown.

Or the programs muchstart with a warning, but don’t work properly (e.g. less):

less

WARNING: terminal is not fully functional

The reason for these error messages is that programs like top, less or vim use information about the terminal you are using to fill the screen and recognize which keys you hit. If this information is not correct, the screen may be messed up or keys may not be recognized.

A quick fix

The quick solution for this problem is very easy – just set the TERM environment variable to xterm after you enter the container:

docker exec -ti <a-docker-container> bash
export TERM=xterm

Animation: Setting the TERM environment variable to fix the "TERM environment variable not set" issue

Setting the TERM environment variable like this only fixes the problem for your current bash session. The next time you enter the container you’ll have to set the environment variable again.

A long-term solution

If you want to prevent setting the TERM environment variable every time you enter a docker container you should always use the -t or --tty flag when executing docker run. This will permanently set the TERM variable for you.

Start the container with the tty flag (docker run -t image)
Use the latest version of Docker (≥1.9)

If you follow these two rules you won’t have to set the TERM environment varibale yourself.

But you will still need the quick-fix from time to time, because not all containers are started with the tty option. Especially noIt seemed to me t if you used a tool like docker-compose to start the containers.

An explanation

Some background on the TERM environment variable and why this problem does not always ocurr.

ansible: assign variable based on condition

You can use the following code snippet:

el_value: "{% if ( nodejs_version.startswith('6.12.') or  nodejs_version.startswith('6.11.') ) %}true{% else %}false{% endif %}"

if nodejs_version.startswith(‘6.12.’) or nodejs_version.startswith(‘6.11.’) condition comes true then the variable will be assigned value true else false

ansible: include variable file based on the first onne available

You can use the following snippet to achieve the above:

- include_vars: "{{ item }}"
  with_first_found:
  - "{{ ansible_distribution }}{{ ansible_distribution_major_version }}.yml"
  - default.yml

bash: check if variable is set

The following is how you can check if variable is set:

if [ ! -z "$VAR1" ] && [ ! -z "$VAR2" ]
then
  echo "Variables VAR1 and VAR2 are set or not empty"
else
  echo "Variables are empty"
fi

Using environment variables in Kubernetes deployment spec

I am concerned about pushing information such as passwords or IP addresses into remote Git repositories. Can I avoid this e.g. by making use of environment variables, e.g. with a deployment spec and actual deployment roughly as follows:

spec:
   type: LoadBalancer
   loadBalancerIP: ${SERVICE_ADDRESS}

and

export SERVICE_ADDRESS=<static-ip-address>
kubectl create -f Deployment.yaml

Obviously this specific syntax does not work yet. But is something like this possible and if so how?

Solution:

In deploy.yml:

LoadbalancerIP: $LBIP

Then just create your env var and run kubectl like this:

export LBIP="1.2.3.4"
envsubst < deploy.yml | kubectl apply -f -


envsubst is available in e.g. Ubuntu/Debian gettext package.

bash: retrieve value of variable whose name is a variable

You can achieve that via:

VAR_NAME=abc

$abc=someval
${!VAR_NAME}

this will give you value “someval”

Using “${a:-b}” for variable assignment in scripts

This technique allows for a variable to be assigned a value if another variable is either empty or is undefined. NOTE: This “other variable” can be the same or another variable.

excerpt

${parameter:-word}
    If parameter is unset or null, the expansion of word is substituted. 
    Otherwise, the value of parameter is substituted.

NOTE: This form also works, ${parameter-word}. If you’d like to see a full list of all forms of parameter expansion available within Bash then I highly suggest you take a look at this topic in the Bash Hacker’s wiki titled: “Parameter expansion“.

Examples

variable doesn’t exist

$ echo "$VAR1"

$ VAR1="${VAR1:-default value}"
$ echo "$VAR1"
default value

variable exists

$ VAR1="has value"
$ echo "$VAR1"
has value

$ VAR1="${VAR1:-default value}"
$ echo "$VAR1"
has value

The same thing can be done by evaluating other variables, or running commands within the default value portion of the notation.

$ VAR2="has another value"
$ echo "$VAR2"
has another value
$ echo "$VAR1"

$

$ VAR1="${VAR1:-$VAR2}"
$ echo "$VAR1"
has another value

More Examples

You can also use a slightly different notation where it’s just VARX=${VARX-<def. value>.

$ echo "${VAR1-0}"
has another value
$ echo "${VAR2-0}"
has another value
$ echo "${VAR3-0}"
0

In the above $VAR1 & $VAR2 were already defined with the string “has another value” but $VAR3was undefined, so the default value was used instead, 0.

Another Example

$ VARX="${VAR3-0}"
$ echo "$VARX"
0

Checking and assigning using `:=` notation

Lastly I’ll mention the handy operator, :=. This will do a check and assign a value if the variable under test is empty or undefined.

Example

Notice that $VAR1 is now set. The operator := did the test and the assignment in a single operation.

$ unset VAR1
$ echo "$VAR1"

$ echo "${VAR1:=default}"
default
$ echo "$VAR1"
default

However if the value is set prior, then it’s left alone.

$ VAR1="some value"
$ echo "${VAR1:=default}"
some value
$ echo "$VAR1"
some value

Handy Dandy Reference Table

References

Ansible cheat sheet

Configuration file

intro_configuration.html

First one found from of

Contents of $ANSIBLE_CONFIG
./ansible.cfg
~/.ansible.cfg
/etc/ansible/ansible.cfg

Configuration settings can be overridden by environment variables – see constants.py in the source tree for names.

Patterns

intro_patterns.html

Used on the ansible command line, or in playbooks.

all (or *)
hostname: foo.example.com
groupname: webservers
or: webservers:dbserver
exclude: webserver:!phoenix
intersection: webservers:&staging

Operators can be chained: webservers:dbservers:&staging:!phoenix

Patterns can include variable substitutions: {{foo}}, wildcards: *.example.com or 192.168.1.*, and regular expressions: ~(web|db).*\.example\.com

Inventory files

intro_inventory.html, intro_dynamic_inventory.html

‘INI-file’ structure, blocks define groups. Hosts allowed in more than one group. Non-standard SSH port can follow hostname separated by ‘:’ (but see also ansible_ssh_port below).

Hostname ranges: www[01:50].example.com, db-[a:f].example.com

Per-host variables: foo.example.com foo=bar baz=wibble

[foo:children]: new group foo containing all members if included groups
[foo:vars]: variable definitions for all members of group foo

Inventory file defaults to /etc/ansible/hosts. Veritable with -i or in the configuration file. The ‘file’ can also be a dynamic inventory script. If a directory, all contained files are processed.

Variable files:

intro_inventory.html

YAML; given inventory file at ./hosts:

./group_vars/foo: variable definitions for all members of group foo
./host_vars/foo.example.com: variable definitions for foo.example.com

group_vars and host_vars directories can also exist in the playbook directory. If both paths exist, variables in the playbook directory will be loaded second.

Behavioral inventory parameters:

intro_inventory.html

ansible_ssh_host
ansible_ssh_port
ansible_ssh_user
ansible_ssh_pass
ansible_sudo_pass
ansible_connection
ansible_ssh_private_key_file
ansible_python_interpreter
ansible_*_interpreter

Playbooks

playbooks_intro.html, playbooks_roles.html

Playbooks are a YAML list of one or more plays. Most (all?) keys are optional. Lines can be broken on space with continuation lines indented.

Playbooks consist of a list of one or more ‘plays’ and/or inclusions:

---
- include: playbook.yml
- <play>
- ...

Plays

playbooks_intro.html, playbooks_roles.html, playbooks_variables.html, playbooks_conditionals.html,playbooks_acceleration.html, playbooks_delegation.html, playbooks_prompts.html, playbooks_tags.html Forum posting Forum postinb

Plays consist of play metadata and a sequence of task and handler definitions, and roles.

- hosts: webservers
  remote_user: root
  sudo: yes
  sudo_user: postgress
  su: yes
  su_user: exim
  gather_facts: no
  accelerate: no
  accelerate_port: 5099
  any_errors_fatal: yes
  max_fail_percentage: 30
  connection: local
  serial: 5
  vars:
    http_port: 80
  vars_files:
    - "vars.yml"
    - [ "try-first.yml", "try-second-.yml" ]
  vars_prompt:
    - name: "my_password2"
      prompt: "Enter password2"
      default: "secret"
      private: yes
      encrypt: "md5_crypt"
      confirm: yes
      salt: 1234
      salt_size: 8
  tags: 
    - stuff
    - nonsence
  pre_tasks:
    - <task>
    - ...
  roles:
    - common
    - { role: common, port: 5000, when: "bar == 'Baz'", tags :[one, two] }
    - { role: common, when: month == 'Jan' }
    - ...
  tasks:
    - include: tasks.yaml
    - include: tasks.yaml foo=bar baz=wibble
    - include: tasks.yaml
      vars:
        foo: aaa 
        baz:
          - z
          - y
    - { include: tasks.yaml, foo: zzz, baz: [a,b]}
    - include: tasks.yaml
      when: day == 'Thursday'
    - <task>
    - ...
  post_tasks:
    - <task>
    - ...
  handlers:
    - include: handlers.yml
    - <task>
    - ...

Using encrypt with vars_prompt requires that Passlib is installed.

In addition the source code implies the availability of the following which don’t seem to be mentioned in the documentation: name, user (deprecated), port, accelerate_ipv6, role_names, and vault_password.

Task definitions

playbooks_intro.html, playbooks_roles.html, playbooks_async.html, playbooks_checkmode.html, playbooks_delegation.html,playbooks_environment.html, playbooks_error_handling.html, playbooks_tags.html ansible-1-5-released Forum posting Ansible examples

Each task definition is a list of items, normally including at least a name and a module invocation:

- name: task
  remote_user: apache
  sudo: yes
  sudo_user: postgress
  sudo_pass: wibble
  su: yes
  su_user: exim
  ignore_errors: True
  delegate_to: 127.0.0.1
  async: 45
  poll: 5
  always_run: no
  run_once: false
  meta: flush_handlers
  no_log: true
  environment: <hash>
  environment:
    var1: val1
    var2: val2
  tags: 
    - stuff
    - nonsence
  <module>: src=template.j2 dest=/etc/foo.conf
  action: <module>, src=template.j2 dest=/etc/foo.conf
  action: <module>
  args:
      src=template.j2
      dest=/etc/foo.conf
  local_action: <module> /usr/bin/take_out_of_pool {{ inventory_hostname }}
  when: ansible_os_family == "Debian"
  register: result
  failed_when: "'FAILED' in result.stderr"
  changed_when: result.rc != 2
  notify:
    - restart apache

delegate_to: 127.0.0.1 is implied by local_action:

The forms <module>: <args>, action: <module> <args>, and local_action: <module> <args> are mutually-exclusive.

Additional keys when_*, until, retries and delay are documented below under ‘Loops’.

In addition the source code implies the availability of the following which don’t seem to be mentioned in the documentation:first_available_file (deprecated), transport, connection, any_errors_fatal.

Roles

playbooks_roles.html

Directory structure:

playbook.yml
roles/
   common/
     tasks/
       main.yml
     handlers/
       main.yml
     vars/
       main.yml
     meta/
       main.yml
     defaults/
       main.yml
     files/
     templates/
     library/

Modules

modules.htm, modules_by_category.html

List all installed modules with

ansible-doc --list

Document a particular module with

ansible-doc <module>

Show playbook snippet for specified module

ansible-doc -i <module>

Variables

playbooks_roles.html, playbooks_variables.html

Names: letters, digits, underscores; starting with a letter.

Substitution examples:

{{ var }}
{{ var["key1"]["key2"]}}
{{ var.key1.key2 }}
{{ list[0] }}

YAML requires an item starting with a variable substitution to be quoted.

Sources:

Highest priority:
- --extra-vars on the command line
General:
- vars component of a playbook
- From files referenced by vars_file in a playbook
- From included files (incl. roles)
- Parameters passed to includes
- register: in tasks
Lower priority:
- Inventory (set on host or group)
Lower priority:
- Facts (see below)
- Any /etc/ansible/facts.d/filename.fact on managed machines (sets variables with `ansible_local.filename. prefix)
Lowest priority
- Role defaults (from defaults/main.yml)

Built-in:

hostvars (e.g. hostvars[other.example.com][...])
group_names (groups containing current host)
groups (all groups and hosts in the inventory)
inventory_hostname (current host as in inventory)
inventory_hostname_short (first component of inventory_hostname)
play_hosts (hostnames in scope for current play)
inventory_dir (location of the inventory)
inventoty_file (name of the inventory)

Facts:

Run ansible hostname -m setup, but in particular:

ansible_distribution
ansible_distribution_release
ansible_distribution_version
ansible_fqdn
ansible_hostname
ansible_os_family
ansible_pkg_mgr
ansible_default_ipv4.address
ansible_default_ipv6.address

Content of ‘registered’ variables:

playbooks_conditionals.html, playbooks_loops.html

Depends on module. Typically includes:

.rc
.stdout
.stdout_lines
.changed
.msg (following failure)
.results (when used in a loop)

See also failed, changed, etc filters.

When used in a loop the result element is a list containing all responses from the module.

Additionally available in templates:

ansible_managed: string containing the information below
template_host: node name of the templateâ��s machine
template_uid: the owner
template_path: absolute path of the template
template_fullpath: the absolute path of the template
template_run_date: the date that the template was rendered

Filters

playbooks_variables.html

{{ var | to_nice_json }}
{{ var | to_json }}
{{ var | from_json }}
{{ var | to_nice_yml }}
{{ var | to_yml }}
{{ var | from_yml }}
{{ result | failed }}
{{ result | changed }}
{{ result | success }}
{{ result | skipped }}
{{ var | manditory }}
{{ var | default(5) }}
{{ list1 | unique }}
{{ list1 | union(list2) }}
{{ list1 | intersect(list2) }}
{{ list1 | difference(list2) }}
{{ list1 | symmetric_difference(list2) }}
{{ ver1 | version_compare(ver2, operator='>=', strict=True }}
{{ list | random }}
{{ number | random }}
{{ number | random(start=1, step=10) }}
{{ list | join(" ") }}
{{ path | basename }}
{{ path | dirname }}
{{ path | expanduser }}
{{ path | realpath }}
{{ var | b64decode }}
{{ var | b64encode }}
{{ filename | md5 }}
{{ var | bool }}
{{ var | int }}
{{ var | quote }}
{{ var | md5 }}
{{ var | fileglob }}
{{ var | match }}
{{ var | search }}
{{ var | regex }}
{{ var | regexp_replace('from', 'to' )}}

See also default jinja2 filters. In YAML, values starting { must be quoted.

Lookups

playbooks_lookups.html

Lookups are evaluated on the control machine.

{{ lookup('file', '/etc/foo.txt') }}
{{ lookup('password', '/tmp/passwordfile length=20 chars=ascii_letters,digits') }}
{{ lookup('env','HOME') }}
{{ lookup('pipe','date') }}
{{ lookup('redis_kv', 'redis://localhost:6379,somekey') }}
{{ lookup('dnstxt', 'example.com') }}
{{ lookup('template', './some_template.j2') }}

Lookups can be assigned to variables and will be evaluated each time the variable is used.

Lookup plugins also support loop iteration (see below).

Conditions

playbooks_conditionals.html

when: <condition>, where condition is:

var == "Vaue", var >= 5, etc.
var, where var coreces to boolean (yes, true, True, TRUE)
var is defined, var is not defined
<condition1> and <condition2> (also or?)

Combined with with_items, the when statement is processed for each item.

when can also be applied to includes and roles. Conditional Imports and variable substitution in file and template names can avoid the need for explicit conditionals.

Loops

playbooks_loops.html

In addition the source code implies the availability of the following which don’t seem to be mentioned in the documentation: csvfile, etcd, inventory_hostname.

Standard:

- user: name={{ item }} state=present groups=wheel
  with_items:
    - testuser1
    - testuser2
   
- name: add several users
  user: name={{ item.name }} state=present groups={{ item.groups }}
  with_items:
    - { name: 'testuser1', groups: 'wheel' }
    - { name: 'testuser2', groups: 'root' }

  with_items: somelist

Nested:

- mysql_user: name={{ item[0] }} priv={{ item[1] }}.*:ALL                
                           append_privs=yes password=foo
  with_nested:
    - [ 'alice', 'bob', 'eve' ]
    - [ 'clientdb', 'employeedb', 'providerdb' ]

Over hashes:

Given

---
users:
  alice:
    name: Alice Appleworth
    telephone: 123-456-7890
  bob:
    name: Bob Bananarama
    telephone: 987-654-3210
    
tasks:
  - name: Print phone records
    debug: msg="User {{ item.key }} is {{ item.value.name }} 
                     ({{ item.value.telephone }})"
    with_dict: users

Fileglob:

- copy: src={{ item }} dest=/etc/fooapp/ owner=root mode=600
  with_fileglob:
    - /playbooks/files/fooapp/*

In a role, relative paths resolve relative to the roles/<rolename>/files directory.

With content of file:

(see example for authorized_key module)

- authorized_key: user=deploy key="{{ item }}"
  with_file:
    - public_keys/doe-jane
    - public_keys/doe-john

See also the file lookup when the content of a file is needed.

Parallel sets of data:

Given

---
alpha: [ 'a', 'b', 'c', 'd' ]
numbers:  [ 1, 2, 3, 4 ]

- debug: msg="{{ item.0 }} and {{ item.1 }}"
  with_together:
    - alpha
    - numbers

Subelements:

Given

---
users:
  - name: alice
    authorized:
      - /tmp/alice/onekey.pub
      - /tmp/alice/twokey.pub
  - name: bob
    authorized:
      - /tmp/bob/id_rsa.pub

- authorized_key: "user={{ item.0.name }} 
                   key='{{ lookup('file', item.1) }}'"
  with_subelements:
     - users
     - authorized

Integer sequence:

Decimal, hexadecimal (0x3f8) or octal (0600)

- user: name={{ item }} state=present groups=evens
  with_sequence: start=0 end=32 format=testuser%02x
      
  with_sequence: start=4 end=16 stride=2
      
  with_sequence: count=4

Random choice:

- debug: msg={{ item }}
  with_random_choice:
     - "go through the door"
     - "drink from the goblet"
     - "press the red button"
     - "do nothing"

Do-Until:

- action: shell /usr/bin/foo
  register: result
  until: result.stdout.find("all systems go") != -1
  retries: 5
  delay: 10

Results of a local program:

- name: Example of looping over a command result
  shell: /usr/bin/frobnicate {{ item }}
  with_lines: /usr/bin/frobnications_per_host 
                       --param {{ inventory_hostname }}

To loop over the results of a remote program, use register: result and then with_items: result.stdout_lines in a subsequent task.

Indexed list:

- name: indexed loop demo
  debug: msg="at array position {{ item.0 }} there is 
                                     a value {{ item.1 }}"
  with_indexed_items: some_list

Flattened list:

---
# file: roles/foo/vars/main.yml
packages_base:
  - [ 'foo-package', 'bar-package' ]
packages_apps:
  - [ ['one-package', 'two-package' ]]
  - [ ['red-package'], ['blue-package']]
  
- name: flattened loop demo
  yum: name={{ item }} state=installed
  with_flattened:
    - packages_base
    - packages_apps

First found:

- name: template a file
  template: src={{ item }} dest=/etc/myapp/foo.conf
  with_first_found:
    - files:
        - {{ ansible_distribution }}.conf
        - default.conf
      paths:
         - search_location_one/somedir/
         - /opt/other_location/somedir/

Command lines

ansible

Usage: ansible <host-pattern> [options]

Options:
  -a MODULE_ARGS, --args=MODULE_ARGS
                        module arguments
  -k, --ask-pass        ask for SSH password
  --ask-su-pass         ask for su password
  -K, --ask-sudo-pass   ask for sudo password
  --ask-vault-pass      ask for vault password
  -B SECONDS, --background=SECONDS
                        run asynchronously, failing after X seconds
                        (default=N/A)
  -C, --check           don't make any changes; instead, try to predict some
                        of the changes that may occur
  -c CONNECTION, --connection=CONNECTION
                        connection type to use (default=smart)
  -f FORKS, --forks=FORKS
                        specify number of parallel processes to use
                        (default=5)
  -h, --help            show this help message and exit
  -i INVENTORY, --inventory-file=INVENTORY
                        specify inventory host file
                        (default=/etc/ansible/hosts)
  -l SUBSET, --limit=SUBSET
                        further limit selected hosts to an additional pattern
  --list-hosts          outputs a list of matching hosts; does not execute
                        anything else
  -m MODULE_NAME, --module-name=MODULE_NAME
                        module name to execute (default=command)
  -M MODULE_PATH, --module-path=MODULE_PATH
                        specify path(s) to module library
                        (default=/usr/share/ansible)
  -o, --one-line        condense output
  -P POLL_INTERVAL, --poll=POLL_INTERVAL
                        set the poll interval if using -B (default=15)
  --private-key=PRIVATE_KEY_FILE
                        use this file to authenticate the connection
  -S, --su              run operations with su
  -R SU_USER, --su-user=SU_USER
                        run operations with su as this user (default=root)
  -s, --sudo            run operations with sudo (nopasswd)
  -U SUDO_USER, --sudo-user=SUDO_USER
                        desired sudo user (default=root)
  -T TIMEOUT, --timeout=TIMEOUT
                        override the SSH timeout in seconds (default=10)
  -t TREE, --tree=TREE  log output to this directory
  -u REMOTE_USER, --user=REMOTE_USER
                        connect as this user (default=jw35)
  --vault-password-file=VAULT_PASSWORD_FILE
                        vault password file
  -v, --verbose         verbose mode (-vvv for more, -vvvv to enable
                        connection debugging)
  --version             show program's version number and exit

ansible-playbook

Usage: ansible-playbook playbook.yml

Options:
  -k, --ask-pass        ask for SSH password
  --ask-su-pass         ask for su password
  -K, --ask-sudo-pass   ask for sudo password
  --ask-vault-pass      ask for vault password
  -C, --check           don't make any changes; instead, try to predict some
                        of the changes that may occur
  -c CONNECTION, --connection=CONNECTION
                        connection type to use (default=smart)
  -D, --diff            when changing (small) files and templates, show the
                        differences in those files; works great with --check
  -e EXTRA_VARS, --extra-vars=EXTRA_VARS
                        set additional variables as key=value or YAML/JSON
  -f FORKS, --forks=FORKS
                        specify number of parallel processes to use
                        (default=5)
  -h, --help            show this help message and exit
  -i INVENTORY, --inventory-file=INVENTORY
                        specify inventory host file
                        (default=/etc/ansible/hosts)
  -l SUBSET, --limit=SUBSET
                        further limit selected hosts to an additional pattern
  --list-hosts          outputs a list of matching hosts; does not execute
                        anything else
  --list-tasks          list all tasks that would be executed
  -M MODULE_PATH, --module-path=MODULE_PATH
                        specify path(s) to module library
                        (default=/usr/share/ansible)
  --private-key=PRIVATE_KEY_FILE
                        use this file to authenticate the connection
  --skip-tags=SKIP_TAGS
                        only run plays and tasks whose tags do not match these
                        values
  --start-at-task=START_AT
                        start the playbook at the task matching this name
  --step                one-step-at-a-time: confirm each task before running
  -S, --su              run operations with su
  -R SU_USER, --su-user=SU_USER
                        run operations with su as this user (default=root)
  -s, --sudo            run operations with sudo (nopasswd)
  -U SUDO_USER, --sudo-user=SUDO_USER
                        desired sudo user (default=root)
  --syntax-check        perform a syntax check on the playbook, but do not
                        execute it
  -t TAGS, --tags=TAGS  only run plays and tasks tagged with these values
  -T TIMEOUT, --timeout=TIMEOUT
                        override the SSH timeout in seconds (default=10)
  -u REMOTE_USER, --user=REMOTE_USER
                        connect as this user (default=jw35)
  --vault-password-file=VAULT_PASSWORD_FILE
                        vault password file
  -v, --verbose         verbose mode (-vvv for more, -vvvv to enable
                        connection debugging)
  --version             show program's version number and exit

ansible-vault

playbooks_vault.html

Usage: ansible-vault [create|decrypt|edit|encrypt|rekey] [--help] [options] file_name

Options:
  -h, --help  show this help message and exit

See 'ansible-vault <command> --help' for more information on a specific command.

ansible-doc

Usage: ansible-doc [options] [module...]

Show Ansible module documentation

Options:
  --version             show program's version number and exit
  -h, --help            show this help message and exit
  -M MODULE_PATH, --module-path=MODULE_PATH
                             Ansible modules/ directory
  -l, --list            List available modules
  -s, --snippet         Show playbook snippet for specified module(s)
  -v                    Show version number and exit

ansible-galaxy

Usage: ansible-galaxy [init|info|install|list|remove] [--help] [options] ...

Options:
  -h, --help  show this help message and exit

  See 'ansible-galaxy <command> --help' for more information on a
  specific command

ansible-pull

Usage: ansible-pull [options] [playbook.yml]

Useful ansible stuff

inventory_hostname

‘inventory_hostname‘ contains the name of the current node being worked on…. (as in, what it is defined in your hosts file as) so if you want to skip a task for a single node –

- name: Restart amavis
  service: name=amavis state=restarted
  when: inventory_hostname != "boris"

(Don’t restart Amavis for boris, do for all others).

You could also use :

...
  when: inventory_hostname not in groups['group_name']
...

if your aim was to (perhaps skip) a task for some nodes in the specified group.

Need to check whether you need to reboot for a kernel update?

If /vmlinuz doesn’t resolve to the same kernel as we’re running
Reboot
Wait 45 seconds before carrying on…

- name: Check for reboot hint.
  shell: if [ $(readlink -f /vmlinuz) != /boot/vmlinuz-$(uname -r) ]; then echo 'reboot'; else echo 'no'; fi
  ignore_errors: true
  register: reboot_hint

- name: Rebooting ...
  command: shutdown -r now "Ansible kernel update applied"
  async: 0
  poll: 0
  ignore_errors: true
  when: kernelup|changed or reboot_hint.stdout.find("reboot") != -1
  register: rebooting

- name: Wait for thing to reboot...
  pause: seconds=45
  when: rebooting|changed

Fixing ~/.ssh/known_hosts

Often an ansible script may create a remote node – and often it’ll have the same IP/name as a previous entity. This confuses SSH — so after creating :

- name: Fix .ssh/known_hosts. (1)
  local_action: command  ssh-keygen -f "~/.ssh/known_hosts" -R hostname

If you’re using ec2, for instance, you could do something like :

- name: Fix .ssh/known_hosts.
  local_action: command  ssh-keygen -f "~/.ssh/known_hosts" -R {{ item.public_ip }} 
  with_items: ec2_info.instances

Where ec2_info is your registered variable from calling the ‘ec2’ module.

Debug/Dump a variable?

- name: What's in reboot_hint?
  debug: var=reboot_hint

which might output something like :

"reboot_hint": {
        "changed": true, 
        "cmd": "if [ $(readlink -f /vmlinuz) != /boot/vmlinuz-$(uname -r) ]; then echo 'reboot'; else echo 'no'; fi", 
        "delta": "0:00:00.024759", 
        "end": "2014-07-29 09:05:06.564505", 
        "invocation": {
            "module_args": "if [ $(readlink -f /vmlinuz) != /boot/vmlinuz-$(uname -r) ]; then echo 'reboot'; else echo 'no'; fi", 
            "module_name": "shell"
        }, 
        "rc": 0, 
        "start": "2014-07-29 09:05:06.539746", 
        "stderr": "", 
        "stdout": "reboot", 
        "stdout_lines": [
            "reboot"
        ]
    }

Which leads on to —

Want to run a shell command do something with the output?

Registered variables have useful attributes like :

changed – set to boolean true if something happened (useful to tell when a task has done something on a remote machine).
stderr – contains stringy output from stderr
stdout – contains stringy output from stdout
stdout_lines – contains a list of lines (i.e. stdout split on \n).

(see above)

- name: Do something
  shell: /usr/bin/something | grep -c foo || true
  register: shell_output

So – we could :

- name: Catch some fish (there are at least 5)
  shell: /usr/bin/somethingelse 
  when: shell_output.stdout > "5"

Default values for a Variable, and host specific values.

Perhaps you’ll override a variable, or perhaps not … so you can do something like the following in a template :

...
max_allowed_packet = {{ mysql_max_allowed_packet|default('128M') }}
...

And for the annoying hosts that need a larger mysql_max_allowed_packet, just define it within the inventory hosts file like :

[linux_servers]
beech
busy-web-server mysql_max_allowed_packet=256M

	gamejudilebaran.word… on Chef: Roles and Environme…
	WARN: Waiting for se… on OSSEC start problem due to…
	aratik711 on Ansible issues
	aratik711 on Chef: Roles and Environme…
	situs judi on Chef: Roles and Environme…

A quick fix

A long-term solution

An explanation

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Examples

More Examples

Another Example

Checking and assigning using := notation

Example

Handy Dandy Reference Table

References

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Configuration file

Patterns

Inventory files

Variable files:

Behavioral inventory parameters:

Playbooks

Plays

Task definitions

Roles

Modules

Variables

Substitution examples:

Sources:

Built-in:

Facts:

Content of ‘registered’ variables:

Additionally available in templates:

Filters

Lookups

Conditions

Loops

Standard:

Nested:

Over hashes:

Fileglob:

With content of file:

Parallel sets of data:

Subelements:

Integer sequence:

Random choice:

Do-Until:

Results of a local program:

Indexed list:

Flattened list:

First found:

Tags

Command lines

ansible

ansible-playbook

ansible-vault

ansible-doc

ansible-galaxy

ansible-pull

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inventory_hostname

Need to check whether you need to reboot for a kernel update?

Fixing ~/.ssh/known_hosts

Debug/Dump a variable?

Want to run a shell command do something with the output?

Default values for a Variable, and host specific values.

Rate this:

Share this:

Checking and assigning using `:=` notation