在某些情况下, 系统无法启动或系统崩溃,我们只能通过重装系统来处理. 但极少数高端机房, 能提供Linux服务器的紧急救援模式RescueLayer, 让你可以ssh进入服务器去尝试修复. 这里我们只是给出机房对RescueLayer 的介绍, 便于参考. 我们并不提供RescueLayer的任何技术支持. 进入RescueLayer后的任何操作都需要您自己完成.

The RescueLayer Kernel is designed to provide our customers with the ability to bring a server online in order to troubleshoot system problems that would normally only be resolved by an OS Reload. The correct RescueLayer Kernel will be selected based upon the currently installed operating system. When the rescue kernel process is initiated, the server will shutdown and reboot on to the public network with the same IP's assigned to the server to allow for remote connections. The root/administrator password will be the same as what is listed in the portal for the server.

Usage:

 The correct RescueLayer Kernel will be selected based upon your currently installed operating system. When the rescue kernel process is initiated, the server will shutdown and reboot on to the public network with the same IP's assigned to the server to allow for remote connections. The root/administrator password will be the same as what is listed in the portal for the server.

Once the server is back online you will connect using SSH as you would normally.

如何判断是紧急救援模式:  The rescue kernel environment will be easy to identify due to the [localhost - **RESCUE**]# prompt.

救援模式的系统文件情况: The root file system is a total of 512Mb. Currently, there will be 75 - 80M free. The ramdisk is mounted read/write so anything written out will be gone upon system reboot.

The tty's on tty1 and tty2 (the vga console) have autologin setup for root, so after boot the customer gets dropped to a root shell.

The tty on ttys1 (SOL console) requires a login.

Yum is functional for the Fedora repositories.

Vi and Nano are installed.

Perl and Python are installed.

Fdisk, Parted, e2fs tools and grub are included.

SSH keys will *not* be the same in the rescue image so expect key mismatch messages. SSH keys are re-generated on each boot.

如何退出救援模式: You will need to reboot your server to drop from the rescue kernel back into your standard operating system. 特别注意: 如果你没有修复好,退出救援模式后,可能也无法正常启动系统. 如果有可能,请务必备份好重要的数据后再重启

救援模式SSH范例图:

softlayer-rescue-kernel.png