本文講述一種實踐方法：將REDHAT Linux系統(包括操作系統,應用程序,數據）從一個物理的系統復制到另一個兼容的物理的系統. 此方法可應用於系統遷移(Server Migration), 系統硬件升級(Server H/W Upgrade), 系統災難恢復(O.S. Disaster Recovery)等.
假定被復制的系統(源系統)為A系統,將要建立的系統(目標系統)為B系統.兩者都采用固定IP.
步驟如下:
1. 在目標系統上安裝小的操作系統
在B系統上安裝一個小的Linux,並配制其網絡.在安裝過程中選擇"Server",且去除X Window, Web, Samba, FTP等.只需建2個分區, /(夠用就行)和swap(亦將在最終系統上被使用).
安裝光盤的版本須與源系統的版本一致.
2. 在目標系統上創建文件系統
按照A系統上的文件系統層次和大小,在B系統上創建相應的相同大小的文件系統.文件系統的大小可根據實際情況作相應調整.
譬如,A系統上有 /, /boot, /tmp, /usr, /var, /var/www, /home, 那麼,在B系統上就創建/x, /x/boot, /x/tmp, /x/usr, /x/var, /x/var/www, /x/home.
此步驟亦可在安裝操作系統時進行.
3. 將數據從源系統復制到目標系統
把操作系統,應用程序及其數據從A系統復制到B系統的新建的相應的文件系統上,並修改/x/etc/fstab.
A:/boot --> B:/x/boot
A:/ --> B:/x
A:/usr --> B:/x/usr
A:/var --> B:/x/var
A:/var/www --> B:/x/var/www
A:/home --> B:/x/home
根文件系統的復制須包括所有在A系統根文件系統上,除了/proc, /tmp, /dev的數據.
將數據從A:/復制到B:/x的命令行大致為(須根據實際情況):
[ B # ] ssh A "cd /; tar -czf - bin etc initrd misc lib sbin root" (cd /x; tar -xzf -)
將數據從A:/boot復制到B:/x/boot的命令行為：
[ B # ] ssh A "cd /; tar -czf - boot" (cd /x; tar -xzf -)
將數據從A:/var/www復制到B:/x/var/www的命令行為：
[ B # ] ssh A "cd /var; tar -czf - www" (cd /x/var; tar -xzf -)
若A:/var上一些大的日志文件或臨時文件無需復制,可用在tar命令行中加--exclude-from：
[ B # ] ssh A "cd /;tar --exclude-from=/home/chinaux/var.exclude -czf" (cd /x; tar -xzf -)
然後在B:/x/var上根據實際需要"toUCh"這些文件.
4. 復制新裝系統的設備文件
在目標系統上將新裝系統的設備文件復制到新建文件系統/x上：
[ B # ] (cd /; tar -czf - dev) (cd /x; tar xzf -)
5. 創建/proc, /tmp等
[ B # ] mkdir -m 755 /x/proc
[ B # ] mkdir -m 755 /x/mnt
[ B # ] mkdir -m 755 /x/mnt/floppy /x/mnt/cdrom
[ B # ] mkdir -m 1777 /x/tmp ## 若/tmp將在根文件系統上
或,
[ B # ] chmod 1777 /x/tmp ## 若/tmp將為一獨立的文件系統
6. 置換設備驅動程序
比較/etc/modules.conf, /x/etc/modules.conf; 比較"lsmod"在系統A和系統B上的輸出. 若兩者使用不同的設備驅動,在系統B上安裝所需設備驅動程序(若有此需要; 安裝的根目錄為/x),修改/etc/modules.conf, 重建RAMDISK(# chroot /x; mkinitrd ...).
通常需要置換設備驅動程序是SCSI,NIC設備驅動.
此步驟可省略若源系統和目標系統的硬件相同或相似.
7. 修改引導菜單,網絡配置
添加復制的操作系統到/boot/grub/grub.conf上(保留其原有行,以防復制的系統不可引導); 修改/x/etc/hosts, /x/etc/sysconfig/network和/x/etc/sysconfig/network-scripts/ifcfg-eth0.
8. 重啟目標系統
重啟B系統,並引導復制的操作系統.若引導失敗,引導至所安裝的小系統,並解決問題.
How to duplicate RedHat to another system
The following describes a workaround to copy a Redhat Linux(inculding applications & data) from one system to another, even they have different models of HDs and different H/W.
Assuming the box to be modelled after is system A, and the system to be built is system B, the prodedure is as follows:
1. create a minimum O.S. on the target system
install mininum Linux on system B with networking enabled(a small / and desired swap, e.g. hda1 & hda2)
2. create file systems on the target system
follow the file system layout on system A to create partions on system B, and mount them, e.g. /mnt/boot, /mnt, /mnt/usr, /mnt/var. /mnt/tmp. re-use the swap, so no need to create a new swap.
note: mount /mnt at first, then create the Directories /mnt/boot, /mnt/usr, etc., and mount the file systems.
3. copy the data from the source system to the target system
copy the O.S. and other data on system A to system B
A: /boot --> B: /mnt/boot
A: /usr --> B: /mnt/usr
A: / (including /sbin, /etc, /bin, /etc, and the other stuff whatever on / file system, except for /proc, /tmp, /dev) --> B: /mnt
A: /var --> B: /mnt/var
the command to copy A:/boot to B:/mnt/boot is
[ system B # ] ssh systemA "cd /; tar czf - boot" (cd /mnt/; tar xzf -)
the command to copy A:/sbin to B:/mnt/sbin is
[ system B # ] ssh systemA "cd /; tar czf - boot" (cd /mnt/; tar xzf -)
4. fix /tmp, /proc, /dev on the target system
[ system B # ] mkdir -m 755 /mnt/proc
[ system B # ] (cd /; tar czf - dev) (cd /mnt/; tar xzf -)
[ system B # ] mkdir -m 1777 /mnt/tmp ## if /tmp will be on / file system
or,
[ system B # ] chmod 1777 /mnt/tmp ## if /tmp will be a seperate file system
5. fix driver issues (scsi driver, NIC drivers, etc)
compare /etc/module.conf & /mnt/etc/module.conf; compare the outputs of "lsmod" on the 2 systems
if a driver is required, install it (the root directory should be changed to /mnt), modify /mnt/etc/modules.conf, rebuild ramdisk image if neccessary(# chroot /mnt; mkinitrd ....)
6. fix bootup, networking & file system table
modify /boot/grub/grub.conf (don't remove the orignial entry in case the duplicated O.S. cannot be booted up), /mnt/etc/fstab, /mnt/etc/hosts, /mnt/etc/sysconfig/network and /mnt/etc/sysconfig/network-scripts/ifcfg-eth0.
7. reboot system B, boot from the duplicated O.S. - done
if the bootup fails, boot it from original minimum O.S., and fix the problems.
