As it happens, I have access to just such a group of machines.
Here's the output from the start of a local bootstrap on an armhf machine. Looks like it does use 'arm' here rather than 'armhf'.
ubuntu@koehler-node0:~$ juju --show-log bootstrap
2014-03-26 15:51:34 INFO juju.cmd supercommand.go:297 running juju-1.17.6-trusty-arm [gc]
2014-03-26 15:51:36 INFO juju.provider.local environprovider.go:147 checking state port
2014-03-26 15:51:36 INFO juju.provider.local environprovider.go:147 checking API port
2014-03-26 15:51:37 INFO juju.provider.local environprovider.go:40 opening environment "local"
2014-03-26 15:51:41 INFO juju.environs.bootstrap synctools.go:34 checking that upload is possible
2014-03-26 15:51:41 INFO juju.environs.bootstrap synctools.go:49 uploading tools for series [trusty precise]
2014-03-26 15:51:41 INFO juju.environs.tools build.go:162 found existing jujud
2014-03-26 15:51:41 INFO juju.environs.tools build.go:172 target: /tmp/juju-tools318320358/jujud
2014-03-26 15:51:58 INFO juju.environs.sync sync.go:296 built tools 1.17.6.1-trusty-arm (6686kB)
2014-03-26 15:51:58 INFO juju.environs.tools simplestreams.go:377 Writing tools/streams/v1/index.json
2014-03-26 15:51:58 INFO juju.environs.tools simplestreams.go:377 Writing tools/streams/v1/com.ubuntu.juju:released:tools.json
2014-03-26 15:51:58 INFO juju.environs.sync sync.go:142 using sync tools source: file:///tmp/480900365/tools
2014-03-26 15:51:58 INFO juju.environs.sync sync.go:65 listing available tools
2014-03-26 15:51:58 INFO juju.environs.sync sync.go:86 found 2 tools
2014-03-26 15:51:58 INFO juju.environs.sync sync.go:96 listing target tools storage
2014-03-26 15:51:58 INFO juju.environs.sync sync.go:109 found 0 tools in target; 2 tools to be copied
2014-03-26 15:51:58 INFO juju.environs.sync sync.go:149 copying 1.17.6.1-precise-arm from file:///tmp/480900365/tools/releases/juju-1.17.6.1-precise-arm.tgz
2014-03-26 15:51:58 INFO juju.environs.sync sync.go:163 copying tools/releases/juju-1.17.6.1-precise-arm.tgz
2014-03-26 15:51:58 INFO juju.environs.sync sync.go:176 downloaded tools/releases/juju-1.17.6.1-precise-arm.tgz (6686kB), uploading
2014-03-26 15:51:58 INFO juju.environs.sync sync.go:177 download 6686kB, uploading
2014-03-26 15:51:58 INFO juju.environs.sync sync.go:149 copying 1.17.6.1-trusty-arm from file:///tmp/480900365/tools/releases/juju-1.17.6.1-trusty-arm.tgz
2014-03-26 15:51:58 INFO juju.environs.sync sync.go:163 copying tools/releases/juju-1.17.6.1-trusty-arm.tgz
2014-03-26 15:51:59 INFO juju.environs.sync sync.go:176 downloaded tools/releases/juju-1.17.6.1-trusty-arm.tgz (6686kB), uploading
2014-03-26 15:51:59 INFO juju.environs.sync sync.go:177 download 6686kB, uploading
2014-03-26 15:51:59 INFO juju.environs.sync sync.go:112 copied 2 tools
2014-03-26 15:51:59 INFO juju.environs.sync sync.go:112 generating tools metadata
2014-03-26 15:51:59 INFO juju.environs.tools simplestreams.go:377 Writing tools/streams/v1/index.json
2014-03-26 15:51:59 INFO juju.environs.tools simplestreams.go:377 Writing tools/streams/v1/com.ubuntu.juju:released:tools.json
2014-03-26 15:51:59 INFO juju.environs.sync sync.go:112 tools metadata written
2014-03-26 15:52:01 INFO juju.environs.bootstrap bootstrap.go:46 bootstrapping environment "local"
2014-03-26 15:52:15 INFO juju.environs.tools tools.go:86 reading tools with major.minor version 1.17
2014-03-26 15:52:15 INFO juju.environs.tools tools.go:94 filtering tools by version: 1.17.6.1
2014-03-26 15:52:15 INFO juju.environs.tools tools.go:97 filtering tools by series: trusty
2014-03-26 15:52:15 INFO juju.environs.tools tools.go:100 filtering tools by architecture: arm
2014-03-26 15:52:15 INFO juju.environs.bootstrap bootstrap.go:58 picked newest version: 1.17.6.1
Logging to /home/ubuntu/.juju/local/log/cloud-init-output.log on remote host
Starting MongoDB server (juju-db-ubuntu-local)
Bootstrapping Juju machine agent
As it happens, I have access to just such a group of machines.
Here's the output from the start of a local bootstrap on an armhf machine. Looks like it does use 'arm' here rather than 'armhf'.
ubuntu@ koehler- node0:~ $ juju --show-log bootstrap 17.6-trusty- arm [gc] .go:147 checking state port .go:147 checking API port .go:40 opening environment "local" bootstrap synctools.go:34 checking that upload is possible bootstrap synctools.go:49 uploading tools for series [trusty precise] tools318320358/ jujud go:377 Writing tools/streams/ v1/index. json go:377 Writing tools/streams/ v1/com. ubuntu. juju:released: tools.json /tmp/480900365/ tools 1-precise- arm from file:// /tmp/480900365/ tools/releases/ juju-1. 17.6.1- precise- arm.tgz juju-1. 17.6.1- precise- arm.tgz juju-1. 17.6.1- precise- arm.tgz (6686kB), uploading /tmp/480900365/ tools/releases/ juju-1. 17.6.1- trusty- arm.tgz juju-1. 17.6.1- trusty- arm.tgz juju-1. 17.6.1- trusty- arm.tgz (6686kB), uploading go:377 Writing tools/streams/ v1/index. json go:377 Writing tools/streams/ v1/com. ubuntu. juju:released: tools.json bootstrap bootstrap.go:46 bootstrapping environment "local" bootstrap bootstrap.go:58 picked newest version: 1.17.6.1 .juju/local/ log/cloud- init-output. log on remote host ubuntu- local)
2014-03-26 15:51:34 INFO juju.cmd supercommand.go:297 running juju-1.
2014-03-26 15:51:36 INFO juju.provider.local environprovider
2014-03-26 15:51:36 INFO juju.provider.local environprovider
2014-03-26 15:51:37 INFO juju.provider.local environprovider
2014-03-26 15:51:41 INFO juju.environs.
2014-03-26 15:51:41 INFO juju.environs.
2014-03-26 15:51:41 INFO juju.environs.tools build.go:162 found existing jujud
2014-03-26 15:51:41 INFO juju.environs.tools build.go:172 target: /tmp/juju-
2014-03-26 15:51:58 INFO juju.environs.sync sync.go:296 built tools 1.17.6.1-trusty-arm (6686kB)
2014-03-26 15:51:58 INFO juju.environs.tools simplestreams.
2014-03-26 15:51:58 INFO juju.environs.tools simplestreams.
2014-03-26 15:51:58 INFO juju.environs.sync sync.go:142 using sync tools source: file://
2014-03-26 15:51:58 INFO juju.environs.sync sync.go:65 listing available tools
2014-03-26 15:51:58 INFO juju.environs.sync sync.go:86 found 2 tools
2014-03-26 15:51:58 INFO juju.environs.sync sync.go:96 listing target tools storage
2014-03-26 15:51:58 INFO juju.environs.sync sync.go:109 found 0 tools in target; 2 tools to be copied
2014-03-26 15:51:58 INFO juju.environs.sync sync.go:149 copying 1.17.6.
2014-03-26 15:51:58 INFO juju.environs.sync sync.go:163 copying tools/releases/
2014-03-26 15:51:58 INFO juju.environs.sync sync.go:176 downloaded tools/releases/
2014-03-26 15:51:58 INFO juju.environs.sync sync.go:177 download 6686kB, uploading
2014-03-26 15:51:58 INFO juju.environs.sync sync.go:149 copying 1.17.6.1-trusty-arm from file://
2014-03-26 15:51:58 INFO juju.environs.sync sync.go:163 copying tools/releases/
2014-03-26 15:51:59 INFO juju.environs.sync sync.go:176 downloaded tools/releases/
2014-03-26 15:51:59 INFO juju.environs.sync sync.go:177 download 6686kB, uploading
2014-03-26 15:51:59 INFO juju.environs.sync sync.go:112 copied 2 tools
2014-03-26 15:51:59 INFO juju.environs.sync sync.go:112 generating tools metadata
2014-03-26 15:51:59 INFO juju.environs.tools simplestreams.
2014-03-26 15:51:59 INFO juju.environs.tools simplestreams.
2014-03-26 15:51:59 INFO juju.environs.sync sync.go:112 tools metadata written
2014-03-26 15:52:01 INFO juju.environs.
2014-03-26 15:52:15 INFO juju.environs.tools tools.go:86 reading tools with major.minor version 1.17
2014-03-26 15:52:15 INFO juju.environs.tools tools.go:94 filtering tools by version: 1.17.6.1
2014-03-26 15:52:15 INFO juju.environs.tools tools.go:97 filtering tools by series: trusty
2014-03-26 15:52:15 INFO juju.environs.tools tools.go:100 filtering tools by architecture: arm
2014-03-26 15:52:15 INFO juju.environs.
Logging to /home/ubuntu/
Starting MongoDB server (juju-db-
Bootstrapping Juju machine agent