Centos5.5下創建無盤系統

 1.          簡介

本文介紹經過VMware創建Centos無盤系統的測試過程

基本實現原理：在Image Server上創建dhcp,tftp,nfs服務，而後啓動diskless client—>dhcp得到IP—>tftp獲取內核文件vmlinuz(可引導的、壓縮的內核), initrd.img(用來臨時的引導硬件到實際內核vmlinuz可以接管並繼續引導的狀態)--->經過nfsroot(Mounting the root filesystem via NFS)來掛載根分區到Image Server上實現無盤系統

 

2.          經過Yum 安裝dhcp,tftp,nfs ,busybox-anaconda(用於redhat的安裝管理程序一個單一的binary,包含大量系統指令,包括shell), system-config-netboot-cmd(用於命令行下創建無盤環境)

l  yum –y install dhcp tftp nfs-utils nfs-utils-lib busybox-anaconda system-config-netboot-cmd

 

3.          修改dhcp配置文件並啓動

l  vi /etc/dhcpd.conf   allow bootp; allow booting;   ddns-update-style interim; ignore client-updates;   subnet 192.168.159.0 netmask 255.255.255.0 { range 192.168.159.200 192.168.159.220; default-lease-time 21600; max-lease-time 43200; option routers 192.168.159.2; option domain-name-servers 192.168.159.2; option subnet-mask 255.255.255.0; option domain-name "pwrd.com"; option time-offset -18000; filename "linux-install/pxelinux.0";  #須要指定pxelinux.0(PXE啓動引導文件)的位置，默認在/tftpboot下 next-server 192.168.159.120;      #指定tftp的IP地址   #能夠指定diskless client的IP地址 host test4 {     hardware ethernet 00:0c:29:a3:86:c3;     fixed-address 192.168.159.130;   } }   #啓動dhcp, 若有報錯能夠查看/var/log/messages 中的log l  /etc/init.d/dhcpd start

 

4.          修改tftp配置文件並啓動

l  vi /etc/xinetd.d/tftp   service tftp {         socket_type             = dgram         protocol                = udp         wait                    = yes         user                    = root         server                  = /usr/sbin/in.tftpd         server_args             = -s /tftpboot  #指定tftp下載的主目錄         disable                 = no      #從yes改成no         per_source              = 11         cps                     = 100 2         flags                   = IPv4 }   #啓動tftp, 若有報錯能夠查看/var/log/messages 中的log l  /etc/init.d/xinetd start

 

5.         創建diskless client所須要的root目錄,並同步系統文件到diskless root目錄中,在根目錄下排除不須要的目錄便可,好比/proc /sys

l  mkdir -p /diskless/centos/test4/root/   #192.168.159.120爲本機,p_w_picpath server l  rsync -v -a -e ssh --exclude='/proc/*' --exclude='/sys/*' --exclude='/mnt/*' 192.168.159.120:/ /diskless/centos/test4/root/

 

6.          修改NFS配置文件,指定掛載目錄,並啓動NFS服務

#snapshot 是爲了那些每個diskless client都須要讀寫的部分，例如/var/log/messages等 l  vi /etc/exports /diskless/centos/test4/root/             *(rw,sync,no_root_squash,no_all_squash) /diskless/centos/test4/root/snapshot/     *(rw,sync,no_root_squash,no_all_squash)   #啓動portmap 和NFS, 若有報錯能夠查看/var/log/messages 中的log /etc/init.d/portmap start /etc/init.d/nfs start   查看rpcinfo和export list rpcinfo –p showmount -e 192.168.159.120

 

 

7.          命令下設置diskless的引導環境

#The 「pxeos」 enables you to create a new operating system under /tftpboot and places the vmlinux and initrd p_w_picpaths there. Options for 「pxeos」: -a: Adds new O.S. -i: Description of O.S. -p: Protocol to use -D: If set to 1, then it indicates it’s diskless -s: NFS server -L: Location of your O.S., this should contain the vmlinuz and initrd somewhere in it. #生成NFS引導的內核文件 l  pxeos -a -i centoskernel -p NFS -D 1 -s 192.168.159.120 -L /diskless/centos/test4 centoskernel   #查看pxeos是否成功 l  pxeos -l   #查看NFS引導的內核文件是否生成 l  ll /tftpboot/linux-install/centoskernel/   #查看pxeos生成的配置文件 l  more /tftpboot/linux-install/pxelinux.cfg/pxeos.xml   The 「pxeboot」 command adds clients to the diskless environment and creates the HEX file for the host in the /tftpboot directory  Options for 「pxeboot」: -a: Adds new host -O: Name of O.S. (You should have already created this with the system-config-netboot or pxeos) -r: Size of ram disk -S: Snapshot name of the diskless client. -e: The interface through which the pxe boot will take place. -N: NIS domain -s: Serial console settings to view remote consoles during boot up #生成diskless client所須要的啓動文件，指定IP爲192.168.159.130 l  pxeboot -a -O centoskernel -r 28753 -S test4 -e eth0 -s console=ttyS0,115200n8r 192.168.159.130   #也能夠不用pxeboot命令，而用01+MAC地址做爲文件名（注意小寫,因爲PXE的尋址規律） l  cat /tftpboot/linux-install/pxelinux.cfg/01-00-0c-29-a3-86-c3 default centoskernel label centoskernel     kernel centoskernel/vmlinuz     append console=ttyS0,9600n8 initrd=centoskernel/initrd.img root=/dev/ram0 init=diskle***c NFSROOT=192.168.159.120:/servers_drbd/centos/coreclient/test4 ramdisk_size=28753 ETHERNET=eth0 SNAPSHOT=test4

 

8.         新建一臺Vmware,只需分配內存和CPU,做爲diskless client

如何獲取MAC地址:

diskless client啓動時會廣播DHCP request, 在Image Server中 tail -f /var/log/messages能夠看到,根據step 7中的格式寫入到/tftpboot/linux-install/pxelinux.cfg中,或者寫入到step 3中的dhcpd.conf,並分配固定IP地址,而後用step 7中的pxeboot生成啓動文件

l  tail -f /var/log/messages Dec 11 00:50:29 test3 dhcpd: DHCPDISCOVER from 00:0c:29:a3:86:c3 via eth0 Dec 11 00:50:29 test3 dhcpd: DHCPOFFER on 192.168.159.130 to 00:0c:29:a3:86:c3 via eth0 Dec 11 00:50:31 test3 dhcpd: DHCPREQUEST for 192.168.159.130 (192.168.159.120) from 00:0c:29:a3:86:c3 via eth0 Dec 11 00:50:31 test3 dhcpd: DHCPACK on 192.168.159.130 to 00:0c:29:a3:86:c3 via eth0   l  ls /tftpboot/linux-install/pxelinux.cfg/01-00-0c-29-a3-86-c3

 

9.          啓動成功後能夠檢查diskless client和p_w_picpath server的同步狀況

因爲NFS設置成了sync模式,則在diskless client上的任何增刪改操做都會實時同步到p_w_picpath server的nfs 掛載目錄

 

 

 

參考資料：

http://www.linuxquestions.org/questions/red-hat-31/building-a-diskless-redhat-enterprise-linux-cluster-765393/

http://wiki.centos.org/zh/HowTos/DisklessClients