使用ansible远程执行命令
1.ansible简介
ansible的官方定义：“Ansible is Simple IT Automation”——简单的自动化IT工具。这个工具的目标：
- 自动化部署APP
- 自动化管理配置项
- 自动化的持续交付
- 自动化的（AWS）云服务管理。
其本质上就是在远程在多台服务器执行一系列命令和文件同步，和以前的介绍的功能类似，他们都是使用ssh协议进行远程操作，但ansible比pssh功能更强大，比如支持主机列表分组、支持playbook模板文件等。本文仅仅介绍ansible的Ad-Hoc用法，即默认的command模块，直接在shell执行命令。
2.安装
ubuntu14.04直接使用apt-get安装：
sudo apt-get install -y ansible
也可以使用pip命令安装：
sudo pip install ansible
为了支持输入远程主机用户密码，还需要安装sshpass工具：
sudo apt-get install -y sshpass
安装完成后创建~/.hosts文件，内容如下:
[local]ceph-0[mon]ceph-1[osd]ceph-2ceph-3
以上配置文件定义了三个主机组，分别为local、mon、osd，ceph-x是主机名。ansible执行需要指定主机列表文件，默认为/etc/hosts,用户也可以通过-i hosts_file指定，我们修改默认文件为我们刚刚创建的新文件，创建~/.ansible.cfg,增加以下内容:
[defaults]hostfile=~/.hosts
3.使用ansible
ansible的简单语法为：
ansible[-f forks] [-m module_name] [-a args]
其中host-pattern指定主机组，比如上面的osd、local等，-f指定并行数，默认为5，-m指定模块名，比如ping表示探测远程主机是否可访问，command表示执行shell命令，copy表示传输文件等，默认为command，-a是指定选项参数，不同的模块具有不同的参数，比如ping不需要选项，command需要指定执行的命令，copy需要指定src和dest等。另外还有以上提到的-i指定主机列表文件、-u指定远程执行用户名等。
uptime操作,远程主机必须有一样的用户名和密码，如果不指定用户名，则默认使用当前登录主机的用户名，否则如果和登录主机用户名不一样，必须通过-u username指定远程主机： ansible osd -a 'uptime'
输出：
ceph-3 | FAILED => SSH encountered an unknown error during the connection. We recommend you re-run the command using -vvvv, which will enable SSH debugging output to help diagnose the issueceph-2 | FAILED => SSH encountered an unknown error during the connection. We recommend you re-run the command using -vvvv, which will enable SSH debugging output to help diagnose the issue
命令执行失败，我们使用-vvvv选项查看详细信息：
ansible -vvvv osd -a 'uptime'
输出：
ebug1: Trying private key: /home/fgp/.ssh/id_rsadebug3: no such identity: /home/fgp/.ssh/id_rsa: No such file or directorydebug1: Trying private key: /home/fgp/.ssh/id_dsadebug3: no such identity: /home/fgp/.ssh/id_dsa: No such file or directorydebug1: Trying private key: /home/fgp/.ssh/id_ecdsadebug3: no such identity: /home/fgp/.ssh/id_ecdsa: No such file or directorydebug1: Trying private key: /home/fgp/.ssh/id_ed25519debug3: no such identity: /home/fgp/.ssh/id_ed25519: No such file or directorydebug2: we did not send a packet, disable methoddebug1: No more authentication methods to try.Permission denied (publickey,password).
说明我们既没有密钥文件也没有输入用户密码，因此无法通过ssh认证，需要输入密码，使用-k选项：
➜ ~ ansible osd -a 'uptime' -kSSH password:ceph-2 | success | rc=0 >> 11:01:17 up 1 day, 6 min, 5 users, load average: 0.02, 0.02, 0.05ceph-3 | success | rc=0 >> 11:01:17 up 1 day, 6 min, 5 users, load average: 0.03, 0.03, 0.05
执行成功了，输入一次密码后，ansible会保存认证session，在session有效期内，不需要重复输入密码，即在执行了以上命令后，不需要再传递-k参数：
➜ ~ ansible osd -a 'uptime'ceph-2 | success | rc=0 >> 11:02:14 up 1 day, 7 min, 5 users, load average: 0.01, 0.02, 0.05ceph-3 | success | rc=0 >> 11:02:14 up 1 day, 7 min, 5 users, load average: 0.01, 0.02, 0.05
有效期只有几分钟时间，为了避免每次输入密码，建议还是通过设置密钥来实现免密码登录，若本地还没有生成密钥文件，则先使用ssh-keygen命令生成密钥文件：
➜ ~ ssh-keygen [1/1877]Generating public/private rsa key pair.Enter file in which to save the key (/home/fgp/.ssh/id_rsa):Enter passphrase (empty for no passphrase):Enter same passphrase again:Your identification has been saved in /home/fgp/.ssh/id_rsa.Your public key has been saved in /home/fgp/.ssh/id_rsa.pub.The key fingerprint is:49:8b:d0:a0:29:69:c8:32:50:3d:fc:8a:0a:4e:c8:1d fgp@ceph-0The key's randomart image is:+--[ RSA 2048]----+|...o. ||+. o+o ||*oo .o. . ||oo E ..o o ||o ..... S ||oo... ||+. ||.. || |+-----------------+
我们把~/.ssh/id_rsa.pub文件拷贝到所有的主机，拷贝文件需要指定-m模块名为copy，指定所有的主机的host-pattern为all:
ansible all -m copy -a 'src=~/.ssh/id_rsa.pub dest=~' -kansible all -a 'ls' -k # 查看是否传输成功
接下来把公钥追加到~/.ssh/authorized_keys中,我们需要执行cat ~/id_rsa.pub >> ~/.ssh/命令，但默认的command模块是不支持重定向和管道的，为了使用重定向和管道，我们使用shell模块：
ansible all -m shell -a 'mkdir -p .ssh' # assure ~/.ssh exist!ansible all -m shell -a 'cat ~/id_rsa.pub >> ~/.ssh/authorized_keys' -k
验证下是否工作，注意下面的命令没有指定-k选项：
ansible all -m shell -a 'cat .ssh/authorized_keys'
输出：
➜ ~ ansible all -m shell -a 'cat .ssh/authorized_keys' [1/1839]ceph-0 | success | rc=0 >>ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQCxjl++nrmghoRVQnnJALR8Ia6eD87hdewZ9XZP9Ay3ZU1eU9F5MF0A7I7UY08kY7az7+14YJeP0T+zhEl8trc6NDV47LJnMG8ONVePokCeCvFgukUa8QpAhMWXSRSyUFA3Q4LpVmRu2nat$lSrwhu0W7uazq9OA5YxSCZRV/lb6bTsrrywBT4s9Crr5DWKUeZ1uKeUVghz0KmxH/ICWyFGE3v3OsqTMvtWM/R5m6FIgb86bd3CsM4UAP4v5I4FEx4+iqsbtvww3qOkY3Qj91AGOuYq8yNhFmQVN7VZZ9OR/8Vc0iI1wOG+vylbEJjr0/pjX$pPzPrOtW0Q6PjTKZXL fgp@ceph-0ceph-3 | success | rc=0 >>ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQCxjl++nrmghoRVQnnJALR8Ia6eD87hdewZ9XZP9Ay3ZU1eU9F5MF0A7I7UY08kY7az7+14YJeP0T+zhEl8trc6NDV47LJnMG8ONVePokCeCvFgukUa8QpAhMWXSRSyUFA3Q4LpVmRu2nat$lSrwhu0W7uazq9OA5YxSCZRV/lb6bTsrrywBT4s9Crr5DWKUeZ1uKeUVghz0KmxH/ICWyFGE3v3OsqTMvtWM/R5m6FIgb86bd3CsM4UAP4v5I4FEx4+iqsbtvww3qOkY3Qj91AGOuYq8yNhFmQVN7VZZ9OR/8Vc0iI1wOG+vylbEJjr0/pjX$pPzPrOtW0Q6PjTKZXL fgp@ceph-0ceph-2 | success | rc=0 >>ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQCxjl++nrmghoRVQnnJALR8Ia6eD87hdewZ9XZP9Ay3ZU1eU9F5MF0A7I7UY08kY7az7+14YJeP0T+zhEl8trc6NDV47LJnMG8ONVePokCeCvFgukUa8QpAhMWXSRSyUFA3Q4LpVmRu2nat$lSrwhu0W7uazq9OA5YxSCZRV/lb6bTsrrywBT4s9Crr5DWKUeZ1uKeUVghz0KmxH/ICWyFGE3v3OsqTMvtWM/R5m6FIgb86bd3CsM4UAP4v5I4FEx4+iqsbtvww3qOkY3Qj91AGOuYq8yNhFmQVN7VZZ9OR/8Vc0iI1wOG+vylbEJjr0/pjX$pPzPrOtW0Q6PjTKZXL fgp@ceph-0ceph-1 | success | rc=0 >>ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQCxjl++nrmghoRVQnnJALR8Ia6eD87hdewZ9XZP9Ay3ZU1eU9F5MF0A7I7UY08kY7az7+14YJeP0T+zhEl8trc6NDV47LJnMG8ONVePokCeCvFgukUa8QpAhMWXSRSyUFA3Q4LpVmRu2nat$lSrwhu0W7uazq9OA5YxSCZRV/lb6bTsrrywBT4s9Crr5DWKUeZ1uKeUVghz0KmxH/ICWyFGE3v3OsqTMvtWM/R5m6FIgb86bd3CsM4UAP4v5I4FEx4+iqsbtvww3qOkY3Qj91AGOuYq8yNhFmQVN7VZZ9OR/8Vc0iI1wOG+vylbEJjr0/pjX$pPzPrOtW0Q6PjTKZXL fgp@ceph-0
可见我们免密码执行远程命令，并且验证了公钥已经追加到~/.ssh/authorized_keys中。
apt-get update -y: ansible all -m shell -a 'apt-get update -y'
输出结果：
ceph-1 | FAILED | rc=100 >>E: Could not open lock file /var/lib/apt/lists/lock - open (13: Permission denied)E: Unable to lock directory /var/lib/apt/lists/E: Could not open lock file /var/lib/dpkg/lock - open (13: Permission denied)E: Unable to lock the administration directory (/var/lib/dpkg/), are you root?ceph-2 | FAILED | rc=100 >>E: Could not open lock file /var/lib/apt/lists/lock - open (13: Permission denied)E: Unable to lock directory /var/lib/apt/lists/E: Could not open lock file /var/lib/dpkg/lock - open (13: Permission denied)E: Unable to lock the administration directory (/var/lib/dpkg/), are you root?ceph-3 | FAILED | rc=100 >>E: Could not open lock file /var/lib/apt/lists/lock - open (13: Permission denied)E: Unable to lock directory /var/lib/apt/lists/E: Could not open lock file /var/lib/dpkg/lock - open (13: Permission denied)E: Unable to lock the administration directory (/var/lib/dpkg/), are you root?
执行失败了，显然是由于没有root权限，需要使用sudo执行命令，需要`--sudo``选项：
ansible all --sudo -m shell -a 'apt-get update -y'
如果没有密钥，需要输入sudo密码，需要指定-K选项（大写的K）。
4.总结
ansible的功能非常强大，以上只介绍了如何在命令行远程执行命令，ansible还有更强大的playbook功能，playbook通过yaml文件定义，类似puppet的模板文件，具体可以参考官方文档。