NAME

tsshbatch - Run Commands On Batches Of Machines

SYNOPSIS

tsshbatch.py [-Nehksv] [-n name] [-p pw] [-H 'h1 h2 ...' | hostlistfile] [command arg ... | -]

DESCRIPTION

tsshbatch is a tool to enable you to issue a command to many hosts without having to log into each one separately. When writing scripts, this overcomes the ssh limitation of not being able to specify the password on the command line.

You can also use tsshbatch to GET and PUT files from- and to many hosts at once.

tsshbatch also understands basic sudo syntax and can be used to access a host, sudo a command, and then exit.

tsshbatch thus allows you to write complex, hands-off scripts that issue commands to many hosts without the tedium of manual login and sudo promotion. System administrators, especially, will find this helpful when working in large host farms.

OPTIONS

tsshbatch supports a variety of options which can be specified on either the command line or in the $TSSHBATCH environment variable:

-G spec
GET file on host and write local dest directory. spec is a quoted pair of strings. The first secifies the path of the source file (on the remote machine) to copy. The second, specifies the destination directory (on the local machine):
tsshbatch.py -G "/foo/bar/baz /tmp" hostlist
This copies /foo/bar/baz from every machine in hostlist to the local /tmp/ directory. Since all the files have the same name, they would overwrite each other if copied into the same directory. So, tsshbatch prepends the string hostname: to the name of each file it saves locally.
-H hostlist
List of hosts on which to run the command. This should be enclosed in quotes so that the list of hosts is handed to the -H option as a single argument:
-H 'host1 host2 host3'
-N Force interactive username dialog
-P spec
PUT file from local machine to remote machine destination directory. spec is a quoted pair of strings. The first secifies the path of the source file (on the local machine) to copy. The second, specifies the destination directory (on the remote machine):
tsshbatch.py -P "/foo/bar/baz /tmp" hostlist
This copies /foo/bar/baz on the local machine to /tmp/ on every host in hostlist.
-e Don't report remote host stderr output

-h Print help information

-k Use ssh keys instead of name/password credentials

-n name Login name to use

-p pw Password to use when logging in and/or doing sudo

-s Force prompting for sudo password

-v Print detailed program version information and exit

The last option on the command line is either an explicit command string or the -. If you provide an explicit command, tsshbatch will attempt to execute it on every host you've specified either via -H or a hostlistfile:

tsshbatch.py -Hmyhost ls -al /etc

This will do a ls -al /etc on myhost.

Be careful when using metacharacters like &&, <<, >>, <, > and so on in your commands. You have to escape and quote them properly or your local shell will interfere with them being properly conveyed to the remote machine.

If tsshbatch sees a - character, it will read commands to execute from stdin. This is the preferred way of doing multiple commands in a single run of tsshbatch:

tsshbatch.py ..... <mycommands

This will read the file mycommands and attempt to execute every line in that file as a command on the remote hosts. Specifying - without such redirection means you want to enter commands manually from the keyboard.

tsshbatch does all the GETs, then all the PUTs before attempting to do any command processing. If no GETs, PUTs, or commands have been specified, tsshbatch will exit silently, since "nothing to do" really isn't an error.

ENVIRONMENT

tsshbatch respects the TSSHBATCH environment variable. You may set this variable with any options above you commonly use to avoid having to key them in each time you run the program. For example:

export TSSHBATCH="-n jluser -p l00n3y"

This would cause all subsequent invocations of tsshbatch to attempt to use the login name/password credentials of jluser and l00n3y respectively.

USE CASES

Different Ways To Specify Targeted Hostnames

There are two ways to specify the list of hosts on which you want to run the specified command:
- On the command line via the -H option:
```
tsshbatch.py -H 'hostA hostB' uname -a
```
  This would run the command uname -a on the hosts hostA and hostB respectively.
  
  Notice that the list of hosts must be separated by spaces but passed as a single argument. Hence we enclose them in single quotes.
- Via a host list file:
```
tsshbatch.py myhosts df -Ph
```
  Here, tsshbatch expects the file myhosts to contain a list of hosts, one per line, on which to run the command df -Ph. As an example, if you want to target the hosts larry, curly and moe in foo.com, myhosts would look like this:
```
larry.foo.com
curly.foo.com
moe.foo.com
```
  This method is handy when there are standard "sets" of hosts on which you regularly work. For instance, you may wish to keep a host file list for each of your production hosts, each of your test hosts, each of your AIX hosts, and so on.
  
  You may use the # comment character freely throughout a host list file to add comments or temporarily comment out a particular host line.
  
  You can even use the comment character to temporarily comment out one or most hosts in the list given to the -H command line argument. For example:
```
tsshbatch.py -H "foo #bar baz" ls
```
  This would run the ls command on hosts foo and baz but not bar. This is handy if you want to use your shell's command line recall to save typing but only want to repeat the command for some of the hosts your originally Specified.
Authentication Using Name And Password

The simplest way to use tsshbatch is to just name the hosts can command you want to run:
```
tsshbatch.py linux-prod-hosts uptime
```
By default, tsshbatch uses your login name found in the $USER environment variable when logging into other systems. In this example, you'll be prompted only for your password which tsshbatch will then use to log into each of the machines named in linux-prod-hosts. (Notice that his assumes your name and password are the same on each host!)

Typing in your login credentials all the time can get tedious after awhile so tsshbatch provides a means of providing them on the command line:
```
tsshbatch.py -n joe.luser -p my_weak_pw linux-prod-hosts uptime
```
This allows you to use tsshbatch inside scripts for hands-free operation.

If your login name is the same on all hosts, you can simplify this further by defining it in the environment variable:
```
export TSSHBATCH="-n joe.luser"
```
Any subsequent invocation of tsshbatch will only require a password to run.

HOWEVER, there is a huge downside to this - your plain text password is exposed in your scripts, on the command line, and possibly your command history. This is a pretty big security hole, especially if you're an administrator with extensive privileges. (This is why the ssh program does not support such an option.) For this reason, it is strongly recommended that you use the -p option sparingly, or not at all. A better way is to push ssh keys to every machine and use key exchange authentication as described below.

However, there are times when you do have use an explicit password, such as when doing sudo invocations. It would be really nice to use -p and avoid having to constantly type in the password. There are two strategies for doing this more securely than just entering it in plain text on the command line:
- Temporarily store it in the environment variable:
```
export TSSHBATCH="-n joe.luser -p my_weak_pw"
```
  Do this interactively after you log in, not from a script (otherwise you'd just be storing the plain text password in a different script). The environment variable will persist as long as you're logged in and disappear when you log out.
  
  If you use this just make sure to observe three security precautions:
  1. Clear your screen immediately after doing this so no one walking by can see the password you just entered.
  2. Configure your shell history system to ignore commands beginning with export TSSHBATCH. That way your plain text password will never appear in the shell command history.
  3. Make sure you don't leave a logged in session unlocked so that other users could walk up and see your password by displaying the environment.
  This approach is best when you want your login credentials available for the duration of an entire login session.
- Store your password in an encrypted file and decrypt it inline.
  
  First, you have to store your password in an encrypted format. There are several ways to do this, but gpg is commonly used:
```
echo "my_weak_pw" | gpg -c >mysecretpw
```
  Provide a decrypt passphrase, and you're done.
  
  Now, you can use this by decrypting it inline as needed:
```
#!/bin/sh
# A demo scripted use of tsshbatch with CLI password passing

MYPW=`cat mysecretpw | gpg`   # User will be prompted for unlock passphrase

sshbatch.py -n joe.luser -p $MYPW hostlist1 command1 arg
sshbatch.py -n joe.luser -p $MYPW hostlist2 command2 arg
sshbatch.py -n joe.luser -p $MYPW hostlist3 command3 arg
```
  This approach is best when you want your login credentials available for the duration of the execution of a script. It does require the user to type in a passphrase to unlock the encrypted password file, but your plain text password never appears in the wild.
Authentication Using Key Exchange

For most applications of tsshbatch, it is much simpler to use key-based authentication. For this to work, you must first have pushed ssh keys to all your hosts. You then instruct tsshbatch to use key-based authentication rather than name and password. Not only does this eliminate the need to constantly provide name and password, it also eliminates passing a plain text password on the command line and is thus far more secure. This also overcomes the problem of having different name/password credentials on different hosts.

By default, tsshbatch will prompt for name and password if they are not provided on the command line. To force key-based authentication, use the -k option:
```
tsshbatch.py -k AIX-prod-hosts ls -al
```
Executing A sudo Command

tsshbatch is smart enough to handle commands that begin with the sudo command. It knows that such commands require a password no matter how you initially authenticate to get into the system. If you provide a password - either via interactive entry or the -p option - by default, tsshbatch will use that same password for sudo promotion. If you provide no password - you're using -k and have not provided a password via -p - tsshbatch will prompt you for the password sudo should use. You can force tsshbatch to ask you for a sudo password with the -s option. This allows you to have one password for intiial login, and a different one for sudo promotion.

Any time you a prompted for a sudo password and a login password has been provided (interactive of -p), you can accept this as the sudo password by just hitting Enter.
Precedence Of Authentication Options

tsshbatch supports these various authentication options in a particular heirarchy using a "first match wins" scheme. From highest to lowest, the precedence is:
1. Key Exchange
2. -n and -p options on command line or in $TSSHBATCH
3. Forced interactive prompting for user name with $USER as the default.
4. Using $USER as the login name and prompting only for password. (Default program behavior).
If try to use Key Exchange and tsshbatch detects a command beginning with sudo, it will prompt you for a password anyway. This is because sudo requires a password to promote privilege.
File Transfers

The -G and -P options specify file GET and PUT respectively. Both are followed by a quoted file transfer specification in the form:
```
"path-to-source-file path-to-destination-directory"
```

Note that this means the file will always be stored under its original name in the destination directory. Renaming isn't possible during file transfer.

However, tsshbatch always does GETs then PUTs then any outstanding command (if any) at the end of the command line. This permits things like renaming on the remote machine after a PUT:
tsshbatch.py -P "foo ./" hostlist mv -v foo foo.has.a.new.name
GETs are a bit of a different story because you are retrieving a file of the same name on every host. To avoid having all but the last one clobber the previous one, tsshbatch makes forces the files you GET to be uniquely named by prepending the hostname and a ":" to the actual file name:
tssbatch.py -H myhost -G "foo ./"
This saves the file myhost:foo in the ./ on your local machine.

The commands do not recognize any special directory shortcut symbols like ~/. You must name file and directory locations using ordinary pathing conventions.

If any file transfer fails, for any reason, the program is aborted and no further work is done.

OTHER

tsshbatch writes the stdout of the remote host(s) to stdout on the local machine. It similarly writes remote stderr output to the local machine's stderr. If you wish to suppress stderr output, either redirect it on your local command line or use the -e option to turn it off entirely.

You will not be able to run remote sudo commands if the host in question enables the Defaults requiretty in its sudoers configuration.

You must have a reasonably current version of Python installed. If your Python installation does not install paramiko you'll have to install it manually, since tsshbatch requires these libraries.

BUGS AND MISFEATURES

When sudo is presented a bad password, it ordinarily prints a string indicating something is wrong. tsshbatch looks for this to let you know that you've got a problem and then terminates further operation. This is so that you do not attempt to log in with a bad password across all the servers you have targeted. (Many enterprises have policies to lock out a user ID after some small number of failed login/access attempts.)

However, some older versions of sudo (noted on a RHEL 4 server running sudo 1.6.7p5) do not return any feedback when presented with a bad password. This means that tsshbatch cannot tell the difference between a successful sudo and a system waiting for you to reenter a proper password. In this situation, if you enter a bad password, the the program will hang. Why? tsshbatch thinks nothing is wrong and waits for the sudo command to complete. At the same time, sudo itself is waiting for an updated password. In this case, you have to kill tsshbatch and start over. This typically requires you to put the program in background (`Ctrl-Z in most shells) and then killing that job from the command line.

There is no known workaround for this problem.

COPYRIGHT AND LICENSING

For terms of use, see the tsshbatch-license.txt file in the program distribution. If you install tsshbatch on a FreeBSD system using the 'ports' mechanism, you will also find this file in /usr/local/share/doc/tsshbatch.

AUTHOR

Tim Daneliuk
tsshbatch@tundraware.com

DOCUMENT REVISION INFORMATION

$Id: tsshbatch.rst,v 1.115 2013/10/23 16:09:28 tundra Exp $

You can find the latest version of this program at:

http://www.tundraware.com/Software/tsshbatch