{"id":1457,"date":"2009-10-10T14:19:15","date_gmt":"2009-10-10T18:19:15","guid":{"rendered":"http:\/\/www.gubatron.com\/blog\/?p=1457"},"modified":"2009-10-10T14:19:15","modified_gmt":"2009-10-10T18:19:15","slug":"map-commands-to-servers-via-ssh","status":"publish","type":"post","link":"https:\/\/www.gubatron.com\/blog\/map-commands-to-servers-via-ssh\/","title":{"rendered":"Quick N Dirty way to Map Commands to remote servers via ssh"},"content":{"rendered":"

You may be running several independent but similar servers at the same time and wasting time by executing commands in all of them one by one.<\/p>\n

Wouldn’t it be nice to send a command to all of them at once? or to monitor all of them at once.<\/p>\n

The following script can be used as a building block to more complex automation tasks for a small size set of servers. (If you’re managing over 50 servers, I’d probably consider looking a different way to arrange servers (map\/reduce cluster), but if you’re doing something below that number this might suffice)<\/p>\n

[code lang=”python”]
\n#!\/usr\/bin\/python <\/p>\n

#########################################################
\n# Author: Angel Leon (gubatron@gmail.com) – October 2009
\n#
\n# Invokes a command locally and invokes the same command
\n# in all machines under the specified username, servers
\n#
\n# Requirement: Have a public ssh_key for that user on all
\n# the other machines so you don’t have to authenticate
\n# on all the other machines.
\n#########################################################
\nimport sys
\nimport os<\/p>\n

# set the username that has access to all the machines here
\nuser=’safeuser’<\/p>\n

# add all your server names here
\nservers=[‘server1.mydomain.com’,’server2.mydomain.com’,’server3.mydomain.com’]<\/p>\n

if __name__ == "__main__":
\n if len(sys.argv) < 2:
\n print "Usage: ssh_map_command <cmd>"
\n sys.exit(0)<\/p>\n

cmd= ‘ ‘.join(sys.argv[1:])<\/p>\n

#Execute locally first
\n print cmd
\n os.system(cmd)<\/p>\n

#Execute for all the servers in the list
\n for server in servers:
\n remote_cmd="ssh %s@%s %s" % (user,server,cmd)
\n print remote_cmd
\n os.system(remote_cmd)
\n print
\n[\/code]<\/p>\n

Save as ssh_map_command and chmod +x it. <\/p>\n

Sample uses<\/strong>
\nCheck the average load of all machines at once (then use output to mitigate high load issues)
\n[code lang=”shell”]$ ssh_map_command uptime[\/code]<\/p>\n

Send HUP signal to all your web servers (put it in an alias or other script… and that’s how you start building more complex scripts)
\n[code lang=”shell”]$ ssh_map_command ps aux | grep [l]ighttpd | kill -HUP `awk {‘print $2’}`[\/code]<\/p>\n

Check if processes are alive, check memory usage on processes across different machines, grep<\/a> remote all logs at once, svn up<\/a> on all machines, rsync<\/a> from one to many, hey, you can even tail -f<\/a> and grep all the logs at once, you can go nuts with this thing. Depends on what you need to do.<\/p>\n

Requirements<\/strong><\/p>\n