Ubuntu Manpage: parallel-ssh — parallel ssh program

NAME

       parallel-ssh — parallel ssh program

SYNOPSIS

       parallel-ssh  [-vAiIP]  [-h hosts_file] [-H [user@]host[:port]] [-g pattern] [-l user] [-p
       par] [-o outdir] [-e errdir] [-t timeout] [-O options] [-x args] [-X arg] command ...

       parallel-ssh -I [-vAiIP] [-h hosts_file] [-H [user@]host[:port]] [-g  pattern]  [-l  user]
       [-p  par]  [-o  outdir]  [-e errdir] [-t timeout] [-O options] [-x args] [-X arg] [command
       ...]

DESCRIPTION

       parallel-ssh is a program for executing ssh in parallel on a number of hosts.  It provides
       features  such as sending input to all of the processes, passing a password to ssh, saving
       output to files, and timing out.

       The PSSH_NODENUM, PSSH_NUMNODES, PSSH_HOST environment variables are sent  to  the  remote
       host.   The  PSSH_NODENUM  variable  is  assigned a unique number for each ssh connection,
       starting with 0 and counting up.  The PSSH_NUMNODES variable is assigned the total  number
       of  node  being used. The PSSH_HOST variable is assigned the name of the host as specified
       in the hosts list.  Note that sshd drops environment variables by default, so  sshd_config
       on the remote host must include the line:
              AcceptEnv PSSH_NODENUM PSSH_NUMNODES PSSH_HOST

OPTIONS

-h host_file
--hosts host_file
Read hosts from the given host_file. Lines in the host file are of the form
[user@]host[:port] and can include blank lines and comments (lines beginning with
"#"). If multiple host files are given (the -h option is used more than once),
then parallel-ssh behaves as though these files were concatenated together. If a
host is specified multiple times, then parallel-ssh will connect the given number
of times.

-H [user@]host[:port]
--host [user@]host[:port]
-H "[user@]host[:port] [ [user@]host[:port ] ... ]"
--host "[user@]host[:port] [ [user@]host[:port ] ... ]"
Add the given host strings to the list of hosts. This option may be given multiple
times, and may be used in conjunction with the -h option.

-g pattern
--host-glob pattern
Filter hosts with glob pattern pattern. This uses the same syntax as shell globs.
Make sure to quote the pattern to prevent shell from expanding it. Examples are
"*web*" and "company_*".

-l user
--user user
Use the given username as the default for any host entries that don't specifically
specify a user.

-p parallelism
--par parallelism
Use the given number as the maximum number of concurrent connections.

-t timeout
--timeout timeout
Make connections time out after the given number of seconds. With a value of 0,
parallel-ssh will not timeout any connections.

-o outdir
--outdir outdir
Save standard output to files in the given directory. Filenames are of the form
[user@]host[:port][.num] where the user and port are only included for hosts that
explicitly specify them. The number is a counter that is incremented each time for
hosts that are specified more than once.

-e errdir
--errdir errdir
Save standard error to files in the given directory. Filenames are of the same
form as with the -o option.

-x args
--extra-args args
Passes extra SSH command-line arguments (see the ssh(1) man page for more
information about SSH arguments). This option may be specified multiple times.
The arguments are processed to split on whitespace, protect text within quotes, and
escape with backslashes. To pass arguments without such processing, use the -X
option instead.

-X arg
--extra-arg arg
Passes a single SSH command-line argument (see the ssh(1) man page for more
information about SSH arguments). Unlike the -x option, no processing is performed
on the argument, including word splitting. To pass multiple command-line
arguments, use the option once for each argument.

-O options
--options options
SSH options in the format used in the SSH configuration file (see the ssh_config(5)
man page for more information). This option may be specified multiple times.

-A
--askpass
Prompt for a password and pass it to ssh. The password may be used for either to
unlock a key or for password authentication. The password is transferred in a
fairly secure manner (e.g., it will not show up in argument lists). However, be
aware that a root user on your system could potentially intercept the password.

-i
--inline
Display standard output and standard error as each host completes.

--inline-stdout
Display standard output (but not standard error) as each host completes.

-v
--verbose
Include error messages from ssh with the -i and -e options.

-I
--send-input
Read input and send to each ssh process. Since ssh allows a command script to be
sent on standard input, the -I option may be used in lieu of the command argument.

-P
--print
Display output as it arrives. This option is of limited usefulness because output
from different hosts are interleaved.

EXAMPLES

       Connect to host1 and host2, and print "hello, world" from each:
              parallel-ssh -i -H "host1 host2" echo "hello, world"

       Print "hello, world" from each host specified in the file hosts.txt:
              parallel-ssh -i -h hosts.txt echo "hello, world"

       Run a command as root with a prompt for the root password:
              parallel-ssh -i -h hosts.txt -A -l root echo hi

       Run a long command without timing out:
              parallel-ssh -i -h hosts.txt -t 0 sleep 10000

       If the file hosts.txt has a large number of entries, say 100, then the parallelism  option
       may also be set to 100 to ensure that the commands are run concurrently:
              parallel-ssh -i -h hosts.txt -p 100 -t 0 sleep 10000

       Run a command without checking or saving host keys:
              parallel-ssh   -i   -H   host1   -H   host2   -x  "-O  StrictHostKeyChecking=no  -O
              UserKnownHostsFile=/dev/null -O GlobalKnownHostsFile=/dev/null" echo hi

       Print the node number for each connection (this will print 0, 1, and 2):
              parallel-ssh -i -H host1 -H host1 -H host2 'echo $PSSH_NODENUM'

TIPS

If you have a set of hosts that you connect to frequently with specific options, it may be
helpful to create an alias such as:
alias parallel-ssh_servers="parallel-ssh -h /path/to/server_list.txt -l root -A"

Note that when an ssh command is terminated, it does not kill remote processes (OpenSSH
bug #396 has been open since 2002). One workaround is to instruct ssh to allocate a
pseudo-terminal, which makes it behave more like a normal interactive ssh session. To do
this, use parallel-ssh's "-x" option to pass "-tt" to ssh. For example:
parallel-ssh -i -x "-tt" -h hosts.txt -t 10 sleep 1000
will ensure that all of the sleep commands will terminate (with SIGHUP) after the 10
second timeout.

By default, ssh uses full buffering for non-interactive commands. Line buffering may be
preferable to full buffering if you intend to look at the files in an output directory as
a command is running. To switch ssh to use line buffering, use its "-tt" option (which
allocates a pseudo-terminal) using the "-x" option in parallel-ssh.

The ssh_config file can include an arbitrary number of Host sections. Each host entry
specifies ssh options which apply only to the given host. Host definitions can even
behave like aliases if the HostName option is included. This ssh feature, in combination
with parallel-ssh host files, provides a tremendous amount of flexibility.

EXIT STATUS

       The exit status codes from parallel-ssh are as follows:

       0      Success

       1      Miscellaneous error

       2      Syntax or usage error

       3      At least one process was killed by a signal or timed out.

       4      All  processes  completed,  but  at  least  one ssh process reported an error (exit
              status 255).

       5      There were no ssh errors, but at least one  remote  command  had  a  non-zero  exit
              status.

AUTHORS

       Written by Brent N. Chun <bnc@theether.org> and Andrew McNabb <amcnabb@mcnabbs.org>.

       https://github.com/lilydjwg/parallel-ssh