99 lines
3.9 KiB
ReStructuredText
99 lines
3.9 KiB
ReStructuredText
Summary
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=======
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.. image:: /images/ucloud.svg
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.. code-block::
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<cli>
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+-------------------------<api>
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| |```````````````|```````````````|
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| <file_scanner> <scheduler> <image_scanner>
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+-------------------------<host>
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Virtual Machine------<init>------<metadata>
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**ucloud-cli** interact with **ucloud-api** to do the following operations:
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- Create/Delete/Start/Stop/Migrate/Probe (Status of) Virtual Machines
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- Create/Delete Networks
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- Add/Get/Delete SSH Keys
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- Create OS Image out of a file (tracked by file_scanner)
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- List User's files/networks/vms
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- Add Host
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ucloud can currently stores OS-Images on
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* File System
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* `CEPH <https://ceph.io/>`_
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**ucloud-api** in turns creates appropriate Requests which are taken
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by suitable components of ucloud. For Example, if user uses ucloud-cli
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to create a VM, **ucloud-api** would create a **ScheduleVMRequest** containing
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things like pointer to VM's entry which have specs, networking
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configuration of VMs.
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**ucloud-scheduler** accepts requests for VM's scheduling and
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migration. It finds a host from a list of available host on which
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the incoming VM can run and schedules it on that host.
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**ucloud-host** runs on host servers i.e servers that
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actually runs virtual machines, accepts requests
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intended only for them. It creates/delete/start/stop/migrate
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virtual machines. It also arrange network resources needed for the
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incoming VM.
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**ucloud-filescanner** keep tracks of user's files which would be needed
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later for creating OS Images.
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**ucloud-imagescanner** converts images files from qcow2 format to raw
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format which would then be imported into image store.
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* In case of **File System**, the converted image would be copied to
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:file:`/var/image/` or the path referred by :envvar:`IMAGE_PATH`
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environement variable mentioned in :file:`/etc/ucloud/ucloud.conf`.
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* In case of **CEPH**, the converted image would be imported into
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specific pool (it depends on the image store in which the image
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belongs) of CEPH Block Storage.
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**ucloud-metadata** provides metadata which is used to contextualize
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VMs. When, the VM is created, it is just clone (duplicate) of OS
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image from which it is created. So, to differentiate between my
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VM and your VM, the VM need to be contextualized. This works
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like the following
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.. note::
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Actually, ucloud-init makes the GET request. You can also try it
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yourself using curl but ucloud-init does that for yourself.
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* VM make a GET requests http://metadata which resolves to actual
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address of metadata server. The metadata server looks at the IPv6
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Address of the requester and extracts the MAC Address which is possible
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because the IPv6 address is
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`IPv6 EUI-64 <https://community.cisco.com/t5/networking-documents/understanding-ipv6-eui-64-bit-address/ta-p/3116953>`_.
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Metadata use this MAC address to find the actual VM to which it belongs
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and its owner, ssh-keys and much more. Then, metadata return these
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details back to the calling VM in JSON format. These details are
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then used be the **ucloud-init** which is explained next.
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**ucloud-init** gets the metadata from **ucloud-metadata** to contextualize
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the VM. Specifically, it gets owner's ssh keys (or any other keys the
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owner of VM added to authorized keys for this VM) and put them to ssh
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server's (installed on VM) authorized keys so that owner can access
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the VM using ssh. It also install softwares that are needed for correct
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behavior of VM e.g rdnssd (needed for `SLAAC <https://en.wikipedia.org/wiki/IPv6#Stateless_address_autoconfiguration_(SLAAC)>`_).
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