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Specifies the name of the administrator account. <br><br>
**Windows-only restriction:** Cannot end in "." <br><br>
**Disallowed values:** "administrator", "admin", "user", "user1",
"test", "user2", "test1", "user3", "admin1", "1", "123", "a", "actuser",
"adm", "admin2", "aspnet", "backup", "console", "david", "guest",
"john", "owner", "root", "server", "sql", "support", "support_388945a0",
"sys", "test2", "test3", "user4", "user5". <br><br>
**Minimum-length (Linux):** 1 character <br><br>
**Max-length (Linux):** 64 characters <br><br> **Max-length
(Windows):** 20 characters <br><br><li> For root
access to the Linux VM, see [Using root privileges on Linux virtual
machines in
Azure](https://docs.microsoft.com/azure/virtual-machines/virtual-machines-linux-use-root-privileges?toc=%2fazure%2fvirtual-machines%2flinux%2ftoc.json)<br><li>
For a list of built-in system users on Linux that should not be used in
this field, see [Selecting User Names for Linux on
Azure](https://docs.microsoft.com/azure/virtual-machines/virtual-machines-linux-usernames?toc=%2fazure%2fvirtual-machines%2flinux%2ftoc.json).