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