SSH连接不持久

Question

I have the following script which SSH's into a network server and executes some commands, for some reason the SSH connection opens but by the time the commands are executed it closes (I think), as a result the commands are failing with below error? Can anyone provide info how to make the SSH connection persistent?

#!/usr/bin/python
import os
import sys
import json
import fileinput
import pwd
from subprocess import Popen, PIPE, STDOUT
import re
import paramiko
import MySQLdb

resource = r'qca-cdit-01'
ssh = paramiko.SSHClient()
ssh.load_system_host_keys()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh.connect(resource, username='username', password='passwordname')
#chan = ssh.get_transport().open_session()
chan = ssh.invoke_shell()
chan.get_pty()

commandstringlist = \
    ['/local/mnt/workspace/LA_host_builds/AU_LINUX_ANDROID_LA.BF64.1.2.1_RB2.05.01.01.081.031_msm8992',
     'cd frameworks/base',
     'git fetch ssh://cdit@review-android.company.com:29418/platform/frameworks/base refs/changes/21/1260821/2 && git cherry-pick FETCH_HEAD']
for cmd_val in commandstringlist:
    #chan.exec_command(cmd_val)
    chan.send(cmd_val)
    print(chan.recv(1024))

error:

Traceback (most recent call last):
  File "ssh_test.py", line 21, in <module>
    chan.get_pty()
  File "/usr/local/lib/python2.7/dist-packages/paramiko/channel.py", line 60, in _check
    return func(self, *args, **kwds)
  File "/usr/local/lib/python2.7/dist-packages/paramiko/channel.py", line 177, in get_pty
    self._wait_for_event()
  File "/usr/local/lib/python2.7/dist-packages/paramiko/channel.py", line 1086, in _wait_for_event
    raise e
paramiko.ssh_exception.SSHException: Channel closed

Answer 1

Every command you execute using exec_command has a channel of its own and therefore a context of its own. That context includes the working directory. You change the working directory in one context and then try to use it in another. Instead, use the same channel for all the commands. You can either open a channel and use it, or just issue all the commands at once.

commandstringlist = ['cd /local/mnt/workspace/test2 && cd data/log && git fetch ssh://username@review-android.company.com:29418/platform/data/log refs/changes/21/1260821/2 && git cherry-pick FETCH_HEAD']

Here are a few other questions that should explain this in more detail.

https://unix.stackexchange.com/questions/80821/why-does-cd-command-not-work-via-ssh https://superuser.com/questions/46851/keeping-working-directory-across-ssh https://stackoverflow.com/a/6770272/492773

Answer 2

The trick is to change to the directory before executing the command. You can easily integrate it into your execute_command :

def execute_command (cmd, pwd=None):
    if pwd:
        cmd = 'cd "%s";%s' % (pwd, cmd)
    print cmd
    si,so,se = ssh.exec_command(cmd) 
    print os.getcwd()
    print "printing so"
    soreadList = so.readlines()
    print soreadList
    print "printing se"
    errList = se.readlines()
    print errList

The command is run by a shell on the remote machine, so any shell tricks like setting environment variables could be added also.

Answer 3

Can anyone provide info how to make the SSH connection persistent?

The following is an example of how to make an SSH connection persistent by attempting to execute a command and then falling back on connecting then executing the command when errors occur.

import paramiko

class sshConnection:
  def __init__( self, host, un, pw ):
    self.host = host
    self.un = un
    self.pw = pw

  def connect( self ):
    self.ssh = paramiko.SSHClient()
    self.ssh.load_system_host_keys()
    self.ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
    self.ssh.connect(self.host, username=self.un, password=self.pw)

  def cmd ( self, cmd, tries=0 ):
    self.si, self.so, self.se = None, None, None
    try:
      self.si, self.so, self.se= self.ssh.exec_command(cmd)
    except Exception, e:
      if tries > 3:
        raise
      self.connect( )
      self.cmd(  cmd, tries+1 )
    return self.si, self.so, self.se



conn = sshConnection( "host","username","password" )

si, out, err = conn.cmd("ls -al")
print "\n".join(map ( lambda x: x.strip(), out.readlines()) )

Answer 4

Simply do :

#!/usr/bin/python
import os
import sys
import json
import fileinput
import pwd
from subprocess import Popen, PIPE, STDOUT
import re
import paramiko
import MySQLdb

resource = r'qca-cdit-01'
ssh = paramiko.SSHClient()
ssh.load_system_host_keys()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh.connect(resource, username='username', password='passwordname')
#chan = ssh.get_transport().open_session()
chan = ssh.invoke_shell()

commandstringlist = \
    ['\n/local/mnt/workspace/LA_host_builds/AU_LINUX_ANDROID_LA.BF64.1.2.1_RB2.05.01.01.081.031_msm8992\n',
     '\ncd frameworks/base\n',
     '\ngit fetch ssh://cdit@review-android.company.com:29418/platform/frameworks/base refs/changes/21/1260821/2 && git cherry-pick FETCH_HEAD\n']
for cmd_val in commandstringlist:
    #chan.exec_command(cmd_val)
    chan.send(cmd_val)
    print(chan.recv(8192))

which worked for me. (You forgot .send() doesn't add lines automatically)