修复错误配置fstab导致系统无法正常启动.doc

修复错误配置fstab文件导致系统无法正常启动1. 问题再现1.1. 操作环境说明 操作系统：CentOS5.2 硬盘分区情况： rootlocalhost # fdisk /dev/sdaThe number of cylinders for this disk is set to 1305.There is nothing wrong with that, but this is larger than 1024,and could in certain setups cause problems with:1) software that runs at boot time (e.g., old versions of LILO)2) booting and partitioning software from other OSs (e.g., DOS FDISK, OS/2 FDISK)Command (m for help): pDisk /dev/sda: 10.7 GB, 10737418240 bytes255 heads, 63 sectors/track, 1305 cylindersUnits = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks IdSystem/dev/sda1 * 1 522 4192933+83Linux/dev/sda2 523 783 2096482+83Linux/dev/sda3 784 914 1052257+82Linux swap / SolarisCommand (m for help): v6288172 unallocated sectors fstab文件：rootlocalhost # more /etc/fstab LABEL=/ / ext3 defaults 1 1LABEL=/tmp /tmp ext3 defaults 1 2tmpfs /dev/shm tmpfs defaults 0 0devpts /dev/pts devptsgid=5,mode=6200 0sysfs /sys sysfs defaults 0 0proc /proc proc defaults 0 0LABEL=SWAP-sda3 swap swap defaults 0 0 1.2. 创建新的分区，并配置fstab文件1.2.1. 创建分区 在/dev/sda上创建新的主分区sda4rootlocalhost # fdisk /dev/sdaThe number of cylinders for this disk is set to 1305.There is nothing wrong with that, but this is larger than 1024,and could in certain setups cause problems with:1) software that runs at boot time (e.g., old versions of LILO)2) booting and partitioning software from other OSs (e.g., DOS FDISK, OS/2 FDISK)Command (m for help): pDisk /dev/sda: 10.7 GB, 10737418240 bytes255 heads, 63 sectors/track, 1305 cylindersUnits = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks IdSystem/dev/sda1 * 1 522 4192933+83Linux/dev/sda2 523 783 2096482+83Linux/dev/sda3 784 914 1052257+82Linux swap / SolarisCommand (m for help): nCommand action e extended p primary partition (1-4)pSelected partition 4First cylinder (915-1305, default 915): Using default value 915Last cylinder or +size or +sizeM or +sizeK (915-1305, default 1305): Using default value 1305Command (m for help): pDisk /dev/sda: 10.7 GB, 10737418240 bytes255 heads, 63 sectors/track, 1305 cylindersUnits = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks IdSystem/dev/sda1 * 1 522 4192933+83Linux/dev/sda2 523 783 2096482+83Linux/dev/sda3 784 914 1052257+82Linux swap / Solaris/dev/sda4 915 1305 3140707+83LinuxCommand (m for help): wThe partition table has been altered!Calling ioctl() to re-read partition table.WARNING: Re-reading the partition table failed with error 16: Device or resource busy.The kernel still uses the old table.The new table will be used at the next reboot.Syncing disks. 创建文件系统，将Label设置为otherrootlocalhost # mke2fs -j -L other /dev/sda4mke2fs 1.39 (29-May-2006)Filesystem label=otherOS type: LinuxBlock size=4096 (log=2)Fragment size=4096 (log=2)393216 inodes, 785176 blocks39258 blocks (5.00%) reserved for the super userFirst data block=0Maximum filesystem blocks=80530636824 block groups32768 blocks per group, 32768 fragments per group16384 inodes per groupSuperblock backups stored on blocks: 32768, 98304, 163840, 229376, 294912Writing inode tables: done Creating journal (16384 blocks): doneWriting superblocks and filesystem accounting information: doneThis filesystem will be automatically checked every 20 mounts or180 days, whichever comes first.Use tune2fs -c or -i to override.rootlocalhost # e2label /dev/sda4other Mount /dev/sda4到 /othersrootlocalhost /# mkdir /othersrootlocalhost /# mount /dev/sda4 /othersrootlocalhost /# mount/dev/sda1 on / type ext3 (rw)proc on /proc type proc (rw)sysfs on /sys type sysfs (rw)devpts on /dev/pts type devpts (rw,gid=5,mode=620)/dev/sda2 on /tmp type ext3 (rw)tmpfs on /dev/shm type tmpfs (rw)none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw)sunrpc on /var/lib/nfs/rpc_pipefs type rpc_pipefs (rw)/dev/sda4 on /others type ext3 (rw)rootlocalhost /# cd /othersrootlocalhost others# ls -ltotal 16drwx- 2 root root 16384 Nov 21 19:35 lost+foundrootlocalhost others# 修改fstab文件rootlocalhost /# vi /etc/fstab LABEL=/ / ext3 defaults 1 1LABEL=/tmp /tmp ext3 defaults 1 2tmpfs /dev/shm tmpfs defaults 0 0devpts /dev/pts devptsgid=5,mode=6200 0sysfs /sys sysfs defaults 0 0proc /proc proc defaults 0 0LABEL=SWAP-sda3 swap swap defaults 0 0LABEL=/other /others ext3 defaults 1 2 请注意：这里用到是LABEL而不是设备名（/dev/sda4），但是这里把卷标写错，应该是other，前面没有 /。 并且没有运行mount -a命令来验证配置是否正确。 接着就直接重启系统了（init 6）。rootlocalhost /# init 6 1.3. 问题的出现1.3.1. 在重启时遇到问题图1.1 系统发现fstab中的LABEL=/other卷标不存在。2. 故障的解决过程2.1. 进入运行级别1 输入root用户密码，进入运行级别1 图2.1 此时试图修改/etc/fstab文件图2.2 此时发现文件系统是只读的 重新mount /图2.3 再次修改fstab文件 图2.4 修改完成，重启系统（init 6）。 系统可以正常启动，问题解决了。图2.53. 问题总结 以上问题的出现是由于错误配置了/e