从centos6升级到centos7步骤

1. 备份

2. 安装依赖列表

yum源文件/etc/yum.repos.d/upgrade.repo，内容为

[upgrade]
name=upgrade
baseurl=http://dev.centos.org/centos/6/upg/x86_64/
enabled=1
gpgcheck=0

安装依赖包

yum install preupgrade-assistant-contents redhat-upgrade-tool preupgrade-assistant

3. 校验升级

执行刚刚安装的命令

preupg

导入yum的GPG密钥

rpm --import http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-7

4. 开始升级

执行升级命令

/usr/bin/redhat-upgrade-tool-cli --force --network 7 --instrepo=http://mirror.centos.org/centos/7/os/x86_64

可以换成阿里云的镜像，速度会快一些

/usr/bin/redhat-upgrade-tool-cli --force --network 7 --instrepo=http://mirrors.aliyun.com/centos/7/os/x86_64/

如果遇到报错

Error: database disk image is malformed

清除缓存，再次重试

yum clean dbcache

5. 重启

reboot