To ensure proper operation of your ECS instance, you must take the considerations outlined in this section into account before use.

Prohibitions

Alibaba Cloud prohibits you from:

• Using your instance for flow-through services. Any violation will result in punishment up to shutdown and lockout of instance, and termination of services.
• Upgrading the ECS kernel or OS without prior authorization.
• Activating SELinux.
• Uninstalling PVDriver.
• Arbitrarily modifying the MAC address of the network adapter.

General operating system considerations

• For an ECS with more than 4 GB RAM, use of a 64-bit OS is recommended, because a 32-bit OS supports a maximum of 4 GB RAM. Currently available 64-bit systems include:
  • Aliyun Linux
  • CoreOS
  • CentOS
  • Debian
  • FreeBSD
  • OpenSUSE
  • SUSE Linux
  • Ubuntu
  • Windows 2008/2012
• 32-bit Windows OS supports CPUs with up to 4 cores.
• To ensure service continuity and avoid service downtime, enable auto-start of service applications upon OS boot.
• For I/O-optimized instances, do not stop the aliyun-service process.

Linux restrictions

To ensure stable system operation, DO NOT:

• Modify the content of the default /etc/issue file. Modifying this file will render management console buttons unusable.
• Modify directory permissions in partitions, particularly permissions for directories such as /etc, /sbin, /bin, /boot, /dev, /usr, and /lib. Improper modification of permissions may cause errors.
• Rename, delete, or disable the Linux root account.
• Compile or perform any other operations on the Linux kernel.
• Enable the NetWorkManager service. This service conflicts with the internal network service of the system and will cause network errors.

Windows restrictions

• Do not close the built-in shutdownmon.exe process. This may delay the restart of your Windows server.
• Do not rename, delete, or disable the Administrator account.
• The use of virtual memory is not recommended.

Pay-As-You-Go restrictions

The Pay-As-You-Go service is subject to the following restrictions:

• An ECS server can use only one billing method, meaning that you cannot switch between Subscription and Pay-As-You-Go services. You cannot modify the configuration of the Pay-As-You-Go service, including upgrades of bandwidth, CPU/memory, and data disks.
• If a fixed 0 Mbps bandwidth is selected, you will not be allocated an external IP address, neither can you upgrade the bandwidth.
• A record-filing service is not offered for Pay-As-You-Go services.
• The fee for Pay-As-You-Go services is calculated per hour as follows: Total fee = CPU fee ＋ memory fee ＋ data disk fee ＋ public bandwidth fee.