There are many ways to run some commands simultaneously on multiple hosts like cssh or dsh. They come handy for example when you are installing software updates on a set of hosts.

dsh is a rather simple comandline tool allowing to execute a command over ssh on multiple hosts. However it doesn't allow any interactive input -- so you can't look at the potentially upgrading packages and press y to accept and you can't go through debconf promts or similar.

This is solved by cssh which opens a XTerm for every host and a input area that is broadcastet to all of them. this is working really well -- you can execute your update on all hosts and still do individual adjustments just as needed: switch focus from the broadcasted input to one of the terminal windows and anything you type just goes there.

Now cssh has a big disadvantage: it requires a running X server (and doesn't do too well with a fullscreen windowmanager). Requiring X is quite a blocker if you need to run that ssh multiplexer on a remote host, for example if the firewalling doesn't allow direct connections. Fortunately you can make tmux behave as we want -- in a simple terminal:

First you need a script spawning the ssh sessions in separate tmux panes and direct input to all of them -- here called ssh-everywhere.sh (you could also write a tmux config I guess):

#/bin/sh
# ssh-everywhere.sh
for i in $HOSTS
do
  tmux splitw "ssh $i"
  tmux select-layout tiled
done
tmux set-window-option synchronize-panes on

Now start the whole thing:

tmux new 'exec sh ssh-everywhere.sh'

And be done.

Update

If you want to type in just one pane (on one host) you can do that as well: C-b : set-window-option synchronize-panes off and moving to the right pane (C-b + Arrow keys)

So this is a collection of things I came about when trying to get a Debian GNU/Hurd virtual machine running with kvm. Most of it is properly documented if you manage to find that particular piece of information.

Kernel Version

Due to a bug in linux 2.6.37 and .38 hurd will only boot if you supply -no-kvm-irqchip which is not that easy if you are using libvirt. A wrapper `kvm` script in the PATH will do, as will using a 2.6.39 kernel.

sudo

sudo will hang before returning from executing some command. I'm now using screen and sudo -i which keeps you a working tty gets you root and hasn't caused mayor trouble yet

sshd

openssh-server won't come up complaining about missing PRNG – and indeed there's no /dev/{u,}random in the default install. fix is to install random-egd from ports.

#!/usr/bin/python

from btsutils.debbugs import debbugs
import mailbox
import re
import sys

mailbox =  mailbox.Maildir(sys.argv[1], factory=False)
bts = debbugs()

for key in mailbox.keys():
    message = mailbox[key]
    if not 'S' in message.get_flags():
        if message['X-Debian-PR-Message']:
            try:
                bugnr = message['X-Debian-PR-Message'].split()[1]
            except IndexError:
                continue
        else:
            test = re.search('Bug#(\d{6})', message['Subject'])
            if test:
                bugnr = test.group(0)[4:]
            else:
                continue

        try:
            bug = bts.get(bugnr)
        except AttributeError:
            print bugnr
            continue

        if bug.getStatus() == u'done':
            message.set_flags(message.get_flags() + 'S')
            mailbox[key] = message


mailbox.flush()

Run it like python cleanbugsmail.py ~/Maildir/.debian.bugs. Anyone aware of a better solution?