使用tar包手工安装多重启动的ubuntu
方案概述
服务器已经安装了CentOS操作系统，由于不能满足开发需求，准备将服务器转换成Ubuntu Server 16.04 LTS。但是，远程服务器依然想保留CentOS作为测试使用，所以部署双操作系统多重启动方案。
远程服务器安装和直接可以物理接触的桌面系统不同，不方便从光盘镜像开始从头安装。所以规划如下安装方案：
如果原操作系统占据了整个磁盘，则通过PXE启动到无盘，然后通过resize方法缩小现有文件系统分区（具体方法和文件系统相关）
空出足够安装新Ubuntu操作系统的分区
线下通过kvm或virtualbox这样的全虚拟化安装一个精简的Ubuntu操作系统，然后通过tar打包方式完整备份整个Ubuntu操作系统
将备份的Ubuntu操作系统tar包上传，并解压缩到对应服务器分区
修订CentOS的grub2配置，加入启动Ubuntu的配置
重启操作系统，选择进入Ubuntu
以上方法避免了在服务器上重新安装Ubnntu的步骤，并且可以作为今后快速部署Ubuntu的方案。
实施步骤
准备
检查操作系统分区划分
#fdisk -l /dev/sda
WARNING: fdisk GPT support is currently new, and therefore in an experimental phase. Use at your own discretion.
Disk /dev/sda: 240.1 GB, 240057409536 bytes, 468862128 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk label type: gpt
# Start End Size Type Name
1 2048 8191 3M BIOS boot parti
2 8192 2105343 1G EFI System
3 2105344 106962943 50G Microsoft basic
4 106962944 111157247 2G Microsoft basic
5 111157248 468860927 170.6G Microsoft basic#df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda3 50G 3.2G 44G 7% /
devtmpfs 126G 0 126G 0% /dev
tmpfs 126G 156K 126G 1% /dev/shm
tmpfs 126G 996K 126G 1% /run
tmpfs 126G 0 126G 0% /sys/fs/cgroup
/dev/sda2 976M 160M 750M 18% /boot#cat /etc/fstab
LABEL=/boot /boot ext4 defaults 1 2
LABEL=/ / ext4 defaults 1 1
LABEL=SWAP swap swap defaults 0 0
...可以看到当前运行的CentOS操作系统使用了/dev/sda3分区，/dev/sda4分区是swap，而/dev/sda5分区虽然划分，但是实际上未被挂载使用。
所以准备删除掉/dev/sda4（需要swapoff /dev/sda4并注释掉/etc/fstab中swap配置行）和/dev/sda5分区，然后再独立创建/dev/sda4分区提供给Ubuntu操作系统使用。
在kvm环境安装Ubuntu系统
virt-install \
--network bridge:virbr0 \
--name ubuntu16 \
--ram=4096 \
--vcpus=2 \
--disk path=/var/lib/libvirt/images/ubuntu16.img,size=20 \
--graphics vnc \
--cdrom=/var/lib/libvirt/images/ubuntu-16.04.3-server-amd64.iso整个安装在一个
/dev/vda1分区使用备份方法参考通过tar备份和恢复整个Linux操作系统
<backuphost>为备份服务器的IP地址，已设置ssh密钥登陆，这样可以免密钥登陆
首先确保能够从虚拟机内部登陆到远程服务器<backuphost>
tar -cvpz --one-file-system / | ssh <backuphost> "( cat > ubuntu16_backup.tar.gz )"使用
tar -cvpz --one-file-system备份整个操作系统会跳过/proc，/sys等目录
恢复ubuntu分区
登陆到目标需要恢复ubuntu的服务器，首先调整空出
/dev/sda4（如上所述）恢复备份
挂载作为ubuntu恢复分区文件系统
mount /dev/sda4 /media使用以下命令恢复
sudo tar -xvpzf /root/ubuntu16_backup.tar.gz -C /media --numeric-owner
-C参数告诉tar命令先变更目录到/media再开始解压缩
修订恢复的ubuntu分区中的
/etc/fstab，这里实际上是修订/media/etc/fstab，使其能够挂载/dev/sda4分区
首先使用blkid获取分区磁盘信息
blkid输出类似
...
/dev/sda4: UUID="79140412-5137-45cc-81a5-58a8a7dac4d9" TYPE="ext4" PARTUUID="a7bfb616-ae18-46a0-9bcc-4207418af8cf"
...注意：在/etc/fstab中使用的是UUID（对比了原先的虚拟机中磁盘命名），所以修改/media/etc/fstab如下：
UUID=79140412-5137-45cc-81a5-58a8a7dac4d9 / ext4 errors=remount-ro 0 1恢复GRUB
Ubuntu 16.4采用了传统的GRUB，可以直接编辑配置文件
/boot/grub/menu.lst，比CentOS 7使用的GRUB 2要简便许多。通过在Ubuntu 16.4中添加CentOS分区中的/boot启动目录下内核，可以在同一个启动菜单中切换不同操作系统。
这里会提示在/etc/default/grub中添加参数，为了能够在串口输出控制台，参考 SerialConsoleHowto
设置串口配置方法和Ubuntu版本有关，获取版本信息的方法是
lsb_release -a，可以看到Ubuntu 16.4代码是xenial
增加ubuntu分区的
/etc/init/ttyS0.conf（实际修改/media/etc/init/ttyS0.conf） - 针对Karmic和更新版本的方法如下
# ttyS0 - getty
#
# This service maintains a getty on ttyS0 from the point the system is
# started until it is shut down again.
start on stopped rc RUNLEVEL=[12345]
stop on runlevel [!12345]
respawn
exec /sbin/getty -L 115200 ttyS0 vt102针对
Edgy/Feisty/Jaunty需要设置/etc/event.d/ttyS0，而针对Darpper或更古老版本则修改/etc/inittab。这里忽略旧版本设置方法，详细请参考SerialConsoleHowto
要使得系统能够启动，需要恢复grub，这里需要编辑
/etc/default/grub（实际配置/media/etc/default/grub）
# If you change this file, run 'update-grub' afterwards to update
# /boot/grub/grub.cfg.
GRUB_DEFAULT=0
GRUB_TIMEOUT=1
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX="console=tty0 console=ttyS0,115200n8"
# Uncomment to disable graphical terminal (grub-pc only)
GRUB_TERMINAL=serial
GRUB_SERIAL_COMMAND="serial --speed=115200 --unit=0 --word=8 --parity=no --stop=1"
# The resolution used on graphical terminal
# note that you can use only modes which your graphic card supports via VBE
# you can see them in real GRUB with the command `vbeinfo'
#GRUB_GFXMODE=640x480
# Uncomment if you don't want GRUB to pass "root=UUID=xxx" parameter to Linux
#GRUB_DISABLE_LINUX_UUID=true通过chroot方式运行ubuntu的grub配置
sudo -s
for f in dev dev/pts proc sys; do mount --bind /$f /media/$f ; done
chroot /media注意，这里 mount 需要包含 /sys ，否则在后面
upgrade-grub会出现大量的device node not found报错。参考: How to restore GRUB after restoring Debian from backup?
手工修改
/boot/grub/menu.lst设置如下
title Ubuntu 16.04.3 LTS, kernel 4.10.0-28-generic
root (hd0)
kernel /boot/vmlinuz-4.10.0-28-generic root=UUID=b513f893-96ca-494c-8634-0ce8eb7dc135 ro console=tty0 console=ttyS0,115200n8
initrd /boot/initrd.img-4.10.0-28-generic
title Ubuntu 16.04.3 LTS, kernel 4.10.0-28-generic (recovery mode)
root (hd0)
kernel /boot/vmlinuz-4.10.0-28-generic root=UUID=b513f893-96ca-494c-8634-0ce8eb7dc135 ro single console=tty0 console=ttyS0,115200n8
initrd /boot/initrd.img-4.10.0-28-generic
title CentOS (3.10.0-327.el7.x86_64) 7.2 (Paladin)
root (hd0)
kernel /boot/vmlinuz-3.10.0-327.el7.x86_64 root=UUID=96219e3e-c371-47a9-baaf-cc2b1b9f8b33 ro crashkernel=auto console=tty0 console=ttyS1,115200
initrd /boot/initramfs-3.10.0-327.el7.x86_64.img最后一项是原CentOS 7搬迁过来的GRUB配置
重新安装一次grub，覆盖原先CentOS的GRUB - 这里参考RecoveringUbuntuAfterInstallingWindows
sudo grub-install /dev/sda重启系统，通过Ubuntu BRUB菜单验证切换操作系统
异常排查
启动提示
error: file /boot/grub/i386-pc/normal.mod' not found.
检查分区
grub rescue> ls
(hd0) (hd0,gpt4) (hd0,gpt3) (hd0,gpt2) (hd0,gpt1) (hd1)
grub rescue> set
cmdpath=(hd0)
prefix=(hd0,gpt4)/boot/grub
root=hd0,gpt4尝试启动 - 参考 AndersonIncorp/fix.sh
grub rescue> set prefix=(hd0,gpt4)/usr/lib/grub
grub rescue> insmod normal但是依然报错
grub rescue> insmod normal
error: file `/usr/lib/grub/i386-pc/normal.mod' not found.参考 GRUB rescue problem after deleting Ubuntu partition! 尝试检查文件系统分区
grub rescue> ls (hd0,gpt1)
(hd0,gpt1): Filesystem is unknown.
grub rescue> ls (hd0,gpt2)
(hd0,gpt2): Filesystem is ext2.
grub rescue> ls (hd0,gpt3)
(hd0,gpt3): Filesystem is ext2.
grub rescue> ls (hd0,gpt4)
(hd0,gpt4): Filesystem is ext2.尝试启动grub
grub rescue> set root=(hd0,gpt4)
grub rescue> set prefix=(hd0,gpt4)/usr/lib/grub
grub rescue> insmod normal
error: file `/boot/grub/i386-pc/normal.mod' not found.如果错误，则重新设置root和prefix，再次尝试上述步骤
grub rescue> set root=(hd0,gpt3)
grub rescue> set prefix=(hd0,gpt3)/usr/lib/grub
grub rescue> insmod normal这次成功了！！！ 这个(hd0,gpt3)分区是原先CentOS的系统分区
继续按照
grub rescue > normal检查分区UUID（可以看到UUID确实是CentOS的系统分区）
grub> ls (hd0,gpt3)
Partition hd0,gpt3: Filesystem type ext* - Label `/' - Last
modification time 2018-01-29 06:43:17 Monday, UUID
96219e3e-c371-47a9-baaf-cc2b1b9f8b33 - Partition start at 1052672KiB - Total
size 52428800KiB
grub>设置启动内核及root分区UUID
linux /boot/vmlinuz-3.10.0-327.el7.x86_64 root=UUID=96219e3e-c371-47a9-baaf-cc2b1b9f8b33 ro console=tty0 console=ttyS1,115200但是这里遇到问题，系统始终报告error: file/boot/vmlinuz-3.10.0-327.el7.x86_64' not found.`
尝试了多次，突然想起来，原先系统安装时候，独立了一个/boot分区，位于/dev/sda2而不是这里的UUID=96219e3e-c371-47a9-baaf-cc2b1b9f8b33对应的/dev/sda3。
所以重新尝试Ubuntu分区
set root=(hd0,gpt4)
set prefix=(hd0,gpt4)/usr/lib/grub
insmod normal
normal检查分区UUID
grub> ls (hd0,gpt4)
Partition hd0,gpt4: Filesystem type ext* - Last modification time
2018-01-28 22:46:34 Sunday, UUID 79140412-5137-45cc-81a5-58a8a7dac4d9 -
Partition start at 53481472KiB - Total size 180949575.5KiB继续加载
linux /boot/vmlinuz-4.10.0-28-generic root=UUID=79140412-5137-45cc-81a5-58a8a7dac4d9 ro console=tty0 console=ttyS0,115200n8也是报错
error: file `/boot/vmlinuz-4.10.0-28-generic' not found.参考 GRUB rescue on legacy BIOS systems
检查所有可用的磁盘分区和文件系统
grub> ls -l
...
error: file `/usr/lib/grub/i386-pc/cpio.mod' not found.
error: file `/usr/lib/grub/i386-pc/cbfs.mod' not found.
error: file `/usr/lib/grub/i386-pc/btrfs.mod' not found.
error: file `/usr/lib/grub/i386-pc/bfs.mod' not found.
error: file `/usr/lib/grub/i386-pc/afs.mod' not found.
error: file `/usr/lib/grub/i386-pc/affs.mod' not found.
No known filesystem detected - Sector size 512B - Total size 234431064KiB
Partition hd0,gpt4: Filesystem type ext* - Last modification time
2018-01-28 22:46:34 Sunday, UUID 79140412-5137-45cc-81a5-58a8a7dac4d9 -
Partition start at 53481472KiB - Total size 180949575.5KiB
Partition hd0,gpt3: Filesystem type ext* - Label `/' - Last
modification time 2018-01-29 06:43:17 Monday, UUID
96219e3e-c371-47a9-baaf-cc2b1b9f8b33 - Partition start at 1052672KiB - Total
size 52428800KiB
Partition hd0,gpt2: Filesystem type ext* - Label `/boot' - Last
modification time 2018-01-29 02:34:03 Monday, UUID
5f67c5f1-be04-406e-964c-f49f8b8e940c - Partition start at 4096KiB - Total size
1048576KiB
Partition hd0,gpt1: No known filesystem detected - Partition start at
1024KiB - Total size 3072KiB
Device hd1: No known filesystem detected - Sector size 512B - Total size
390711384KiB尝试启动
set root=(hd0,4)
linux (hd0,4)/boot/vmlinuz-4.10.0-28-generic root=UUID=b513f893-96ca-494c-8634-0ce8eb7dc135 ro console=tty0 console=ttyS0,115200n8
initrd (hd0,4)/boot/initrd.img-4.10.0-28-generic依然找不到
发现可以通过指定
(hd0,2)包含CentOS/boot分区来启动
grub> set root=(hd0,3)
grub> linux (hd0,2)/vmlinuz-3.10.0-327.ali2014.alios7.x86_64 root=UUID=96219e3e-c371-47a9-baaf-cc2b1b9f8b33 ro console=tty0 console=ttyS1,115200
grub> initrd (hd0,2)/initramfs-3.10.0-327.el7.x86_64.img然后可以尝试启动CentOS系统了
grub> bootCentOS启动
CentOS启动
...
[ 185.715802] dracut-initqueue[749]: Warning: dracut-initqueue timeout - starting timeout scripts
[ 186.221782] dracut-initqueue[749]: Warning: dracut-initqueue timeout - starting timeout scripts
[ 186.727769] dracut-initqueue[749]: Warning: dracut-initqueue timeout - starting timeout scripts
[ 187.233784] dracut-initqueue[749]: Warning: dracut-initqueue timeoWarning: /dev/disk/by-uuid/96219e3e-c371-47a9-baaf-cc2b1b9f8b33 does not exist
Generating "/run/initramfs/rdsosreport.txt"
Entering emergency mode. Exit the shell to continue.
Type "journalctl" to view system logs.
You might want to save "/run/initramfs/rdsosreport.txt" to a USB stick or /boot
after mounting them and attach it to a bug report.
dracut:/#重新开始
reboot之后重新开始
检查当前配置：
grub rescue> set
cmdpath=(hd0)
prefix=(hd0,gpt3)/boot/grub
root=hd0,gpt3grub rescue> ls
(hd0) (hd0,gpt4) (hd0,gpt3) (hd0,gpt2) (hd0,gpt1) (hd1)加载grub模块
grub rescue> set prefix=(hd0,gpt3)/usr/lib/grub
grub rescue> insmod normal
grub rescue> normal进入常规模式后，检查设备uuuid
grub> ls -l
Device hd0: No known filesystem detected - Sector size 512B - Total size
234431064KiB
Partition hd0,gpt4: Filesystem type ext* - Last modification time
2018-01-28 22:46:34 Sunday, UUID 79140412-5137-45cc-81a5-58a8a7dac4d9 -
Partition start at 53481472KiB - Total size 180949575.5KiB
Partition hd0,gpt3: Filesystem type ext* - Label `/' - Last
modification time 2018-01-29 06:43:17 Monday, UUID
96219e3e-c371-47a9-baaf-cc2b1b9f8b33 - Partition start at 1052672KiB - Total
size 52428800KiB
Partition hd0,gpt2: Filesystem type ext* - Label `/boot' - Last
modification time 2018-01-29 02:34:03 Monday, UUID
5f67c5f1-be04-406e-964c-f49f8b8e940c - Partition start at 4096KiB - Total size
1048576KiB
Partition hd0,gpt1: No known filesystem detected - Partition start at
1024KiB - Total size 3072KiB
Device hd1: No known filesystem detected - Sector size 512B - Total size
390711384KiBgrub> linux (hd0,2)/vmlinuz-3.10.0-327.ali2014.alios7.x86_64 root=/dev/sda3 ro console=tty0 console=ttyS1,115200
grub> initrd (hd0,2)/initramfs-3.10.0-327.el7.x86_64.img不知道为何Ubuntu使用的是 ttyS1，而不是ttyS0。如果设置了
ttyS0反而无法显示输出信息
参考
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