Ansible
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In this section, some aspects on ansible is discussed.
file
copy
command
cron: name attr must be specfied, otherwise, the crontab task shall be added repeatedly
debug: msg info to be printed
user
service
setup: get basic facts as variables collecting from nodes, note the key prefix ansible_ is not used
template: backup=yes
authorized_keys
lineinfile: When modifying a line the regexp should typically match both the initial state of the line as well as its state after replacement by line to ensure idempotence. Insert lines logic:
apt
make
hostname
: mysql-python package missing issue: , apt: name=python3-mysqldb state=present is enough, however pip install mysql-python wouldn't work.
pip
set_fact: set varible per host and used later in playbooks
: Using ansible to deploy gluster fs
when: the argument is rendered by jinja2, but no need for bracket or, and, not
compare operator in general language is ok to use in the condition statement, linke !=, >=
changed_when, failed_when
loop: list or list of hash, corresponding variables in leading task
some moudules directly support list argument
register of a loop task, has attr results as a list
environment: config the env variables, http_proxy:http://blah, play level or task level
become: the user after ssh
remote_user: the user used for ssh
ansible-vault, encrypt protected info by given password, used as !value|eencrypted strings in playbooks
ansible-galaxy init: create the directory structure for ansible roles
ansible-playbook -e "var=value", overwrite var with highest priority
-vv: verbose mode
example: ansible -i ~/hpc/hosts cn -m apt -a "name=iperf state=present" --become -K
eg. ansible -i ./hosts cn[1:2] -m service -a "name=ganglia-monitor state=restarted" --become -K
Jinja template rendering only happen before the task is sent to nodes.
int, string to int
to_json, to_yaml, from_json, from_yaml
default(val) for default value of undefined variables, default(omit) use default value from external such as system defaults
min, flatten, flatten(levels=1)
unique, union(list), intersect(list), difference(list), symmetric_difference(list)
"{{mac_prefix| random_mac}}"
"{{ 60|random }}", "{{ [1,2,3]|random }}"
"{{ list|shuffle }}"
log(3), default base is e, pow(5), root(3), default power is 2, abs, round
hash, arguments can be sha1 or md5 or more choices. password_hash('sha256', 'mysecretsalt')
{{dict|combine(dict2)}} similar to dict.update(dict2) in python
regex_search('regexpr'), regex_search('regexpr', new)
Example
Future plan: a spack module for ansible (settled by changed_when to avoid changed report of command)
molecule: full stack to test ansible
In template system, just use {{}} instead of quote "" outside.
ansible_facts, the key should rip the ansible part off, which is ...
but for host_vars[hostname] to access the facts, the ansible prefix is must, which is in contrast with ansible_facts...
lookup plugin dont take become: yes as a thing, it just cannot cat other user's file….
for copy to copy files without permission, use remote_src: yes option, otherwise become is also useless...
the dest path cannot be a relative one, but use {{role_path}} instead
{{ D['key']|default ('undefined') }} can be used as default value for non existing keys of dict
In general, ansible playbooks is definitely a type of domain specific language (DSL). There are so many fields, that config files (json or yaml) have been evolving into DSL which go far beyond the scope of some nouns, but also complicated adjective and verbs in the configurations. In some sense, it is always a question, that whether such a scheme is really simple and efficient enough as claimed? Maybe, say playbooks in this case, is easier to handle and suitable for more complicated cases when implemented directly as python scripts instead of a indirect level of abstraction (yml, which one needs reinvent basically all wheels of grammars in a Turing complete language like if and for, and still has less expression power than a Turing complete language). Of course, it is just my personal thought.
with_items, register.results is automatically a list, see
nested loop, use jinja template as "{{ ['alice', 'bob'] |product(['clientdb', 'employeedb', 'providerdb'])|list }}", see .
host pattern in ansible adhoc: . As quoted "You can refer to hosts within the group by adding a subscript to the group name", that is to say, the pattern is group[1:2] instead of c[1:2] as host names.
, --check in cli args, no real change happen but only reported as a simulation, also --diff to show difference
"{{json or yml data| json_query("query pattern")}}", this query pattern is backend with
ipaddr, ipv4, ipv6, return bool default, but can extract more info if arguments are given, see
parse_cli("spec") parse output by given spec file, for details of syntax, see
urlsplit get info from url by given arguments, see
indent in jinja template config files:
each task has it own ssh session and shell: . The default shell of ansible is sh, while source is a bash builtin instead of sh.
differece between command and shell module: . Command is weaker, it doesn't support evaluation on env vars and no support for |, & like things in shell.
Hostname is not persistent due to cloud init system in ubuntu, see .
default_ipv4 item in ansible fact could be empty, dont rely on this variable to setup networks. It seems that there is value only after dhclient <nic>? It is actually the default route ip, see .