For the detailed information about how to create a VM instance on ZStack Cloud, and how to use an installation image to boot the VM instance, see the chapter "Create a VM Instance" in User Guide.

To enable the VM instance created with the template to automatically obtain an IP address, you need to modify the NIC configurations. Run the following commands:

[root@localhost ~]# sed -i '/ONBOOT=/cONBOOT=yes' /etc/sysconfig/network-scripts/ifcfg-ens3     #Set the NIC to be activated automatically at boot [root@localhost ~]# sed -i '/^UUID'/d /etc/sysconfig/network-scripts/ifcfg-ens3    #Delete the UUID in the NIC configuration file [root@localhost ~]# sed -i '/^HWADDR'/d /etc/sysconfig/network-scripts/ifcfg-ens3    #Delete the MAC in the NIC configuration file

To ensure the customized configuration features such as User Data and SSH Public Key are available when you create a VM instance with the template, you need to install the cloud-init before encapsulating the template. We recommend that you install the cloud-init of 0.7.9, 17.1, 19.4 or latter versions. You can select and install the version you need.

For CentOS 8.x, closing the patches for spectre and meltdown can effectively improve the performance of the VM instances. To close the patches, follow these steps:

1. Check whether the patch is on.
   Run grep . /sys/devices/system/cpu/vulnerabilities/*. You can check whether the patch is on by viewing /sys. For example:

   # grep . /sys/devices/system/cpu/vulnerabilities/* /sys/devices/system/cpu/vulnerabilities/itlb_multihit:KVM: Mitigation: Split huge pages /sys/devices/system/cpu/vulnerabilities/l1tf:Mitigation: PTE Inversion; VMX: conditional cache flushes, SMT disabled /sys/devices/system/cpu/vulnerabilities/mds:Mitigation: Clear CPU buffers; SMT Host state unknown /sys/devices/system/cpu/vulnerabilities/meltdown:Mitigation: PTI /sys/devices/system/cpu/vulnerabilities/spec_store_bypass:Mitigation: Speculative Store Bypass disabled via prctl and seccomp /sys/devices/system/cpu/vulnerabilities/spectre_v1:Mitigation: usercopy/swapgs barriers and __user pointer sanitization /sys/devices/system/cpu/vulnerabilities/spectre_v2:Mitigation: Full generic retpoline, IBPB: conditional, IBRS_FW, STIBP: disabled, RSB filling /sys/devices/system/cpu/vulnerabilities/srbds:Not affected /sys/devices/system/cpu/vulnerabilities/tsx_async_abort:Mitigation: Clear CPU buffers; SMT Host state unknown

   You can check the patch status through the last result returned. Mitigation means that the patch is on, while vulnerable means the patch is closed.

2. View the vulnerability fix method.
   If the patch is on, check the bug fix method through the last result returned in the previous step. There are two bug fix methods: Retpoline without IBPB and Enhanced IBRS.

   • Retpoline without IBPB: This method has a smaller impact on the performance of the system. You can either close the patch or keep it on. This depends on your needs.
   • Enhanced IBRS: This method has a greater impact on the performance of the system. We recommend that you close the patch to improve the system performance. (The performance can improve by about 30% as measured.)
3. Close the vulnerability patch.
   To close the vulnerability patch, following these steps:

   1. In the /etc/default/grub file, set the value as noibrs noibpb nopti spectre_v2=off nospectre_v1 l1tf=off nospec_store_bypass_disable no_stf_barrier mds=off mitigations=off for the parameter GRUB_CMDLINE_LINUX.
   2. Run grub2-mkconfig > /boot/grub2/grub.cfg to apply the configuration.
   3. Reboot the VM instance to make the configuration effective.

   Refer to the following example:

   [root@10-0-5-87 ~]# cat /etc/default/grub      #view /etc/default/grub file configuration.Make configurations based on your needs. GRUB_TIMEOUT=5 GRUB_DISTRIBUTOR="$(sed 's, release .*$,,g' /etc/system-release)" GRUB_DEFAULT=saved GRUB_DISABLE_SUBMENU=true GRUB_TERMINAL_OUTPUT="console" GRUB_CMDLINE_LINUX="crashkernel=auto rd.lvm.lv=zstack/root rd.lvm.lv=zstack/swap rhgb quiet noibrs noibpb nopti spectre_v2=off nospectre_v1 l1tf=off nospec_store_bypass_disable         no_stf_barrier mds=off mitigations=off" GRUB_DISABLE_RECOVERY="true" [root@10-0-5-87 ~]# grub2-mkconfig > /boot/grub2/grub.cfg     #Apply the configuration [root@10-0-5-87 ~]# reboot     #Restart the VM instance to make the configuration effective

On the displayed page, set the following parameters:

• Name: Enter a name for the image.
• Description: Optional. Enter a description for the image.
• Image Type: Select System Image here.
• Backup Storage: Select a backup storage created before.

You can use the image exported to create VM instances on other cloud platforms directly. The method to export images varies according to backup storage types.

• ImageStore backup storage.

  On the Image page, choose Actions > Export Image. This button helps export the image.

  After generating the image, you can copy the URL of the image exported on the Overview page to download the image. Or, you can copy the URL of the exported image on the Exported page. You can also click Download on the page to download the image directly.

• Ceph backup storage. If you use a Ceph backup storage, you can export the image on the UI or from the backup storage.
  • Export on the UI:

    On the Image page, choose Actions > Export Image. This button helps export the image.

    After generating the image, you can copy the URL of the image exported on the Overview page to download the image. Or, you can copy the URL of the exported image on the Exported page. You can also click Download on the page to download the image directly.

  • Export from the backup storage:
    1. On the Overview page of the created image, copy Installation Path.
    2. Login to the terminal of the Ceph backup storage, run rbd export to export the image. For example:
       If you obtain the installation path ceph://bak-t-cac5eee23a204c1a914d1743f1584644/7232237c0059409babcd1c7a69452b98, you can run the following commands to export the image:

       [root@ceph-node1 ~]# rbd export bak-t-cac5eee23a204c1a914d1743f1584644/7232237c0059409babcd1c7a69452b98 /root/export-test.qcow2 [root@ceph-node1 ~]# # bak-t indicates the installation path of the image [root@ceph-node1 ~]# # /root/export-test.qcow2 indicates the target path and the file name of the exported image

       Note: The command rbd export does not include such a prefix as ceph://.