Remote

Just like running local commands, Plumbum supports running commands on remote systems, by executing them over SSH.

Remote Machines

Forming a connection to a remote machine is very straight forward:

>>> from plumbum import SshMachine
>>> rem = SshMachine("hostname", user = "john", keyfile = "/path/to/idrsa")
>>> # ...
>>> rem.close()

Or as a context-manager:

>>> with SshMachine("hostname", user = "john", keyfile = "/path/to/idrsa") as rem:
...     pass

Note

SshMachine requires ssh (openSSH or compatible) installed on your system in order to connect to remote machines. The remote machine must have bash as the default shell (or any shell that supports the 2>&1 syntax for stderr redirection). Alternatively, you can use the pure-Python implementation of ParamikoMachine.

Only the hostname parameter is required, all other parameters are optional. If the host has your id-rsa.pub key in its authorized_keys file, or if you’ve set up your ~/.ssh/config to login with some user and keyfile, you can simply use rem = SshMachine("hostname").

Much like the local object, remote machines expose which(), path(), python, cwd and env. You can also run remote commands, create SSH tunnels, upload/download files, etc. You may also refer to the full API, as this guide will only survey the features.

Note

PuTTY users on Windows should use the dedicated PuttyMachine instead of SshMachine. See also ParamikoMachine.

New in version 1.0.1.

Working Directory and Environment

The cwd and env attributes represent the remote machine’s working directory and environment variables, respectively, and can be used to inspect or manipulate them. Much like their local counterparts, they can be used as context managers, so their effects can be contained.

>>> rem.cwd
<Workdir /home/john>
>>> with rem.cwd(rem.cwd / "Desktop"):
...     print rem.cwd
/home/john/Desktop
>>> rem.env["PATH"]
/bin:/sbin:/usr/bin:/usr/local/bin
>>> rem.which("ls")
<RemotePath /bin/ls>

Tunneling

SSH tunneling is a very useful feature of the SSH protocol. It allows you to connect from your machine to a remote server process, while having your connection authenticated and encrypted out-of-the-box. Say you run on machine-A, and you wish to connect to a server program running on machine-B. That server program binds to localhost:8888 (where localhost refers naturally to to machine-B). Using Plumbum, you can easily set up a tunnel from port 6666 on machine-A to port 8888 on machine-B:

>>> tun = rem.tunnel(6666, 8888)
>>> # ...
>>> tun.close()

Or as a context manager:

>>> with rem.tunnel(6666, 8888):
...     pass

You can now connect a socket to machine-A:6666, and it will be securely forwarded over SSH to machine-B:8888. When the tunnel object is closed, all active connections will be dropped.

Remote Commands

Like local commands, remote commands are created using indexing ([]) on a remote machine object. You can either pass the command’s name, in which case it will be resolved by through which, or the path to the program.

>>> rem["ls"]
<RemoteCommand(<RemoteMachine ssh://hostname>, '/bin/ls')>
>>> rem["/usr/local/bin/python3.2"]
<RemoteCommand(<RemoteMachine ssh://hostname>, '/usr/local/bin/python3.2')>
>>> r_ls = rem["ls"]
>>> r_grep = rem["grep"]
>>> r_ls()
u'foo\nbar\spam\n'

Nesting Commands

Remote commands can be nested just like local ones. In fact, that’s how the SshMachine operates behind the scenes - it nests each command inside ssh. Here are some examples:

>>> r_sudo = rem["sudo"]
>>> r_ifconfig = rem["ifconfig"]
>>> print r_sudo[r_ifconfig["-a"]]()
eth0      Link encap:Ethernet HWaddr ...
[...]

You can nest multiple commands, one within another. For instance, you can connect to some machine over SSH and use that machine’s SSH client to connect to yet another machine. Here’s a sketch:

>>> from plumbum.cmd import ssh
>>> print ssh["localhost", ssh["localhost", "ls"]]
/usr/bin/ssh localhost /usr/bin/ssh localhost ls
>>>
>>> ssh["localhost", ssh["localhost", "ls"]]()
u'bin\nDesktop\nDocuments\n...'

Piping

Piping works for remote commands as well, but there’s a caveat to note here: the plumbing takes place on the local machine! Consider this code for instance

>>> r_grep = rem["grep"]
>>> r_ls = rem["ls"]
>>> (r_ls | r_grep["b"])()
u'bin\nPublic\n'

Although r_ls and r_grep are remote commands, the data is sent from r_ls to the local machine, which then sends it to the remote one for running grep. This will be fixed in a future version of Plumbum.

It should be noted, however, that piping remote commands into local ones is perfectly fine. For example, the previous code can be written as

>>> from plumbum.cmd import grep
>>> (r_ls | grep["b"])()
u'bin\nPublic\n'

Which is even more efficient (no need to send data back and forth over SSH).

Paramiko Machine

New in version 1.1.

SshMachine relies on the system’s ssh client to run commands; this means that for each remote command you run, a local process is spawned and an SSH connection is established. While relying on a well-known and trusted SSH client is the most stable option, the incurred overhead of creating a separate SSH connection for each command may be too high. In order to overcome this, Plumbum provides integration for paramiko, an open-source, pure-Python implementation of the SSH2 protocol. This is the ParamikoMachine, and it works along the lines of the SshMachine:

>>> from plumbum.machines.paramiko_machine import ParamikoMachine
>>> rem = ParamikoMachine("192.168.1.143")
>>> rem["ls"]
RemoteCommand(<ParamikoMachine paramiko://192.168.1.143>, <RemotePath /bin/ls>)
>>> r_ls = rem["ls"]
>>> r_ls()
u'bin\nDesktop\nDocuments\nDownloads\nexamples.desktop\nMusic\nPictures\n...'
>>> r_ls("-a")
u'.\n..\n.adobe\n.bash_history\n.bash_logout\n.bashrc\nbin...'

Note

Using ParamikoMachine requires paramiko to be installed on your system. Also, you have to explicitly import it (from plumbum.machines.paramiko_machine import ParamikoMachine) as paramiko is quite heavy.

Refer to the API docs for more details.

The main advantage of using ParamikoMachine is that only a single, persistent SSH connection is created, over which commands execute. Moreover, paramiko has a built-in SFTP client, which is used instead of scp to copy files (employed by the .download()/.upload() methods), and tunneling is much more light weight: In the SshMachine, a tunnel is created by an external process that lives for as long as the tunnel is to remain active. The ParamikoMachine, however, can simply create an extra channel on top of the same underlying connection with ease; this is exposed by connect_sock(), which creates a tunneled TCP connection and returns a socket-like object

Warning

Piping and input/output redirection don’t really work with ParamikoMachine commands. You’ll get all kinds of errors, like 'ChannelFile' object has no attribute 'fileno' or I/O operation on closed file – this is due to the fact that Paramiko’s channels are not real, OS-level files, so they can’t interact with subprocess.Popen.

This will be solved in a future release; in the meanwhile, you can use the machine’s .session() method, like so

>>> s = mach.session()
>>> s.run("ls | grep b")
(0, u'bin\nPublic\n', u'')

Tunneling Example

On 192.168.1.143, I ran the following sophisticated server (notice it’s bound to localhost):

>>> import socket
>>> s=socket.socket()
>>> s.bind(("localhost", 12345))
>>> s.listen(1)
>>> s2,_=s.accept()
>>> while True:
...     data = s2.recv(1000)
...     if not data:
...         break
...     s2.send("I eat " + data)
...

On my other machine, I connect (over SSH) to this host and then create a tunneled connection to port 12345, getting back a socket-like object:

>>> rem = ParamikoMachine("192.168.1.143")
>>> s = rem.connect_sock(12345)
>>> s.send("carrot")
6
>>> s.recv(1000)
'I eat carrot'
>>> s.send("babies")
6
>>> s.recv(1000)
'I eat babies'
>>> s.close()

Remote Paths

Analogous to local paths, remote paths represent a file-system path of a remote system, and expose a set of utility functions for iterating over subpaths, creating subpaths, moving/copying/ renaming paths, etc.

>>> p = rem.path("/bin")
>>> p / "ls"
<RemotePath /bin/ls>
>>> (p / "ls").is_file()
True
>>> rem.path("/dev") // "sd*"
[<RemotePath /dev/sda>, < RemotePath /dev/sdb>, <RemotePath /dev/sdb1>, <RemotePath /dev/sdb2>]

Note

See the Utilities guide for copying, moving and deleting remote paths

For futher information, see the api docs.