Advanced Advanced Namespaces: 5 namespaces, 2 nodes What happens in this demo:
- Two machines boot, the second as a tcp cpu from the first machine's disk fs
- Each machine starts an additional namespace on the local display using a live cd
- Now there are 5 independent namespaces: 1 disk root, 1 labs cd, 1 9front cd, 2 ram/paq service ns
- Next the disk and cd namespace connect to a shared hubfs and create persistent shells
- This makes persistent shells in every namespace available in every other namespace
- The tcp cpu imports the /proc from the other server and locates a 9front process and a service ns process
- The tcp cpu uses cpns to rewrite the namespace of the other machine's ramrooted process to be inside the 9front namespace
- The user on the labs machine imports and mounts the 9front cd and uses rerootwin to enter that namespace
- The five independent namespaces hosted on the two nodes all coexist and the user can share resources between them as needed
- The user can enter any namespace with rerootwin
- Within each namespace, the user can access and control the other namespaces via hubfs
- The disk and cd namespaces behave normally for the user and use their normal default configuration
This demo shows a more elaborate use of ANTS. This will show how multiple namespaces on different machines can be created, connected, and entered freely by the user. The exact setup used - a hard drive and 2 cds - is not intended as a practical model - these could be any root fses of any type, local or network, on any medium. This walkthrough was constructed to use cd .iso images because they are consistently available and demonstrate the principles, which can be applied to any root fs.
Not getting lost
Interacting with this many namespaces at once can be disorienting even for experienced Plan 9 users. Here is a summary of how the namespaces in this demo are accessed:
- Cpu port 17010 accesses a tcp root namespace with a disk fs from the other server
- Cpu port 17020 accesses the service namespace of the fileserver providing the disk root
- Cpu port 17060 accesses the service namespace of the tcp boot cpu
- The console of the file server will be taken over by a 9front live cd terminal namespace
- The console of the tcp cpu will be taken over by a Bell Labs live cd terminal namespace
The machine which boots first and runs the disk fossil will be called filesrv and the machine which boots second as a tcp cpu will be called helix
From within these namespaces, additional connections will be made using hubfs. The hubfs will allow shells from each namespace to be accessed from the same hub. The user can also move between namespaces using the rerootwin script. The demo will put you in namespaces where you cpu to machine A, enter a namespace hosted on machine B, and then use hubfs to access an entirely different namespace C.
The fact that you can "get lost" in all this is a feature, not a bug - the transparency and seamlessness of the environment is the whole point! This particular example may seem contrived at first - a "namespace maze" - but it was created to demonstrate the principles involved. The ability to create namespaces, edit them, and move between them is generally useful and the essence of Plan 9. The techniques in this demo can be applied to standard configurations such as venti -> fossil -> tcp cpu -> terminal.
Start by booting both nodes in the manner of the earlier tutorial boot 9queen with option 2 boot 9worker option 3 cpu to worker port 17010
You have cpu'd into a totally conventional tcp boot cpu namespace.
Now start an additional cd namespace on each machine
These commands are entered on the "console" of each machine, which will be referred to as the "gui" display following.
mv /srv/boot /srv/diskboot #on filesrv
9660srv -f /dev/sdD0/data boot
interactive=yes
. /bin/plan9rc
change the first line on helix to:
mv /srv/boot /srv/tcpboot #on helix cpu
While re-executing the plan9rc, enter "clear" for all the options (x7) until the "getrootfs" option, and then answer "srv". For the next question, hit enter to accept the default /srv/boot. Then "clear" for next answer, and for "rootstart" choose "terminal".
This will start a new namespace rooted on the live cd on each machine. The existing cpu namespace is unchanged.
Now move the original /srv/boot back. On filesrv
mv /srv/boot /srv/front
mv /srv/diskboot /srv/boot
Repeat this on helix
mv /srv/boot /srv/labs
mv /srv/tcpboot /srv/boot
inside the front cd namespace on the fossil server (gui display)
mount -a /srv/bootpaq /bin
mount -c /srv/hubfs /n/hubfs
hub
%local front
This mounts the hubfs and shares a shell from the current 9front namespace to it.
In 9worker cpu tcp namespace (port 17010)
import -c filesrv /srv /n/fsrv
mount -c /n/fsrv/hubfs /n/fhubs
srvfs fhubs /n/fhubs
bind -c /n/fhubs /n/hubfs
hub
%local tcphelix
Inside a shell inside the labs cd namespace on helix (gui display)
mount -a /srv/bootpaq /bin
mount -c /srv/fhubs /n/hubfs
hub
%local labs
now cpu into the 'service namespace' on port 17060 of the tcp cpu server
import filesrv /srv /n/fsrv
mount -c /n/fsrv/hubfs /n/hubfs
hub
%attach front
Both machines can now make use of all the namespaces easily via the shared hubfs.
modifying the ns of remote processes
We will demonstrate modifying the namespace of processes on a remote box via /proc.
cpu to filesrv 17020 service namespace
Start grio and then in a sub window
echo $pid
In 9front cd namespace, do the same in another new shell
echo $pid
in helix 17060 service ns
import -a filesrv /proc
(make sure the import of the namespace isnt duplicating the pid of the above processes, do ps -a and make sure these process IDs arent duplicated. If they are, repeat the process of making new shells in the two different namespaces and checking the pids until you get ones that arent overlapping.)
Now copy the namespace of the 9front cd shell onto the rootless shell
cpns -t -r 9frontpid servicepid
cpns -r 9frontpid servicepid
Now check the changed namespace in the first shell
theo
games/packet
Rerootwin to an alternate remote ns
This example is similar to the one-machine example with a live cd, but it reroots to the cd namespace hosted on the other machine.
In helix 17060 ns
mntgen -s slashmnt /mnt && chmod 666 /srv/slashmnt
mntgen -s mntexport /mnt/exportfs && chmod 666 /srv/mntexport
import filesrv /srv /n/fsrv
mount -c /n/fsrv/front /n/front
srvfs localfront /n/front
rerootwin -f localfront
service=con
. $home/lib/profile
import filesrv /srv /n/fsrv
mount -c /n/fsrv/hubfs /n/hubfs
grio
Now we are inside the 9front cd namespace, served to us from the 'tcp cpu' and we have access to all the other namespaces via the Hub menu.
What else is part of the Advanced Namespaces ToolS?
Many uses of ANTS are left out of these tutorials. Most important for practical use are the venti and fossil tools. In the author's usage, the multiple namespaces are not attached cds - they are independent chains of venti-fossil servers. The ventiprog and cpsys(not to be confused with cpns) scripts back up data between ventis and make the same rootscore available from different fossils. This means that additional independent namespaces with the same data are available for backup and for testing or simple parallelization.
The ANTS boot system (the plan9rc, ramskel, and initskel scripts primarily) has many options and aims to be backwards-compatible with all existing x86 pc boot options. It is possible to attach to a root fs in new ways, such as connecting to a u9fs server and then choosing a particular subdirectory to root from rather than using the root of the entire u9fs system.
ANTS has several other scripts and use modes. The scripts getdevs and savedevs are related to rerootwin and perform the "device saving and retrieval" without using newns to enter a new independent namespace. They are often useful in combination with shell s inside hubfs, to allow them to track window width correctly. Scripts such as addwrroot attach to file or cpu servers to make use of their resources without rerooting fully. Hubfs is general purpose network piping in addition to persistent shells and has several tricks of its own.
The full Advanced Namespace ToolS website at http://ants.9gridchan.org (also available with 9fs ants.9gridchan.org or ftpfs ants.9gridchan.org) has the source code, compiled kernel and tools, and much more documentation including the full Attack of the Giant Ants! paper.