下载地址：
CentOS6：http://cloud.centos.org/centos/6/images/
CentOS7：http://cloud.centos.org/centos/7/images/
Ubuntu14.04：http://cloud-images.ubuntu.com/trusty/current/
Ubuntu16.04：http://cloud-images.ubuntu.com/xenial/current/
修改密码：
原文：https://access.redhat.com/discussions/664843
在使用QEMU或在QEMU-KVM时，如果不知道下载的image文件的root用户的密码，可以使用guestfish工具去修改。
- Using “guestfish” to change the Password for the root account:
-
1）You can use guestfish to edit a running system under KVM virtualization
2）You can use “guestfish” to edit the /etc/shadow file and change the root password.
3）Guestfish is an interactive shell that you can use from the command line or from shell scripts to access guest virtual machine file systems. (See example below): - 安装guestfish：
-
yum -y install guestfish//RHEL
yum -y install libguestfs-tools//FEDORA
Import the qcow2 image into KVM. The image will be named something
along the lines of: “rhel-guest-image-7.1-20150224.0.x86_64.qcow2”, (as
of July 2nd, 2015, the version will of course change over time)
Change the password on the newly imported KVM to get on the pre-built system.
Example steps to change the root password using guestfish:
This set of instructions is for use on the host system that has the kvm RHEL 7 guest.
The syntax is: guestfish –rw -a
(Note, your system may be /dev/vda1, mine was /dev/sda1. Use the ‘list-filesystems’ command)
root@box1 # guestfish --rw -a ./rhel-guest-image-7.1-20150224.0.x86_64.qcow2
><fs> run
><fs> list-filesystems
><fs> mount /dev/sda1 /
><fs> vi /etc/shadow
><fs>quit //退出
>
//可以在其他命令行下面，使用下面的命令生成新密码
[root@someothersystem ~]# openssl passwd -1 changeme
$1$QiSwNHrs$uID6S6qOifSNZKzfXsmQG1