Several system failures and solutions

Computer shop news: UNIX several system failures and solutions One of the faults After turning on the computer power, the following message appears on the main console screen: boot not found cannot open Stage 1 boot failure: error loading Hd (40) /boot, then crash. Analysis: This indicates that the Boot file in the root directory of the system is missing. Boot is an interactive program for loading and executing UNIX programs, mainly for loading and executing the core of the UNIX operating system. During the boot process, Boot will read /etc/default/boot, display boot process information, load and execute /unix. Therefore, when the Boot file is damaged, the system will fail to boot. Solution: 1. Insert the Boot disk into the drive and re-power the machine. At this point, boot from the Boot disk. 2. Type hd(40)/unix at the system boot prompt. This command is used to boot the UNIX core from the hard disk. Load. Then enter the Root password to enter single-user mode, the super user prompt # appears; 3. Install the Boot disk to the hard disk with the command, mount /dev/fd0135ds18/mnt, and then use the command: cp/mnt/boot/to restore the hard disk. The Boot file in the root directory; 4. Use the command umount/dev/fd0135ds18 to remove the Boot disk from the hard disk; 5. Type haltsys to shut down the system, and then remove the Boot disk, the fault is removed, the system can boot normally; After the system boots normally, enter the super user, and change the owner and group of the /boot file to the bin defined by the system. Fault 2 After the machine is powered up, the following message appears on the main console screen: unix not found, then crashes. Analysis: This indicates that the UNIX core is missing. Because /unix contains the core, damage to the unix file will cause the system to fail to load the parallel kernel, causing a crash. Solution: 1. Insert the Boot disk into the drive and re-power the machine. At this time, boot from the Boot disk. 2. At the system boot prompt, type: fd(64) unix root=hd(40) swap=hd(41 ) pipe=hd(40) or just type fd(64)/unix. This command is used to load the UNIX kernel from the Boot disk, and then enter the Root password to enter the single-user mode. At this time, the superuser prompt # appears; 3. Mount the Boot disk to the hard disk with the command mount/dev/fd0135ds18/mnt. Then use the command: cp /mnt /unix /restore the Unix file in the root directory of the hard disk; 4. Use the command umount /dev /fd0135ds18 to remove the Boot disk from the hard disk; 5. Type haltsys to shut down the system, remove the Boot disk, then the fault Exclude, the system can boot normally; 6. After the system boots normally, enter the super user, and change the owner and group of the /unix file to the bin and mem defined by the system. Fault 3 After the machine is powered up, type the Enter key at the system boot prompt. When the first screen is refreshed, the second screen appears with many error messages, such as: INIT: command exec /etc/brc 1>/dev/Console 2>&&1 failed to execute, errno=9 (exec of shell failed) … Analysis: This indicates that the system /bin/sh file is corrupted or missing. Because sh is an interpreter for Shell standards, job control, and restrictive commands, damage or loss to the file will cause the system to fail to start. Solution: 1. Insert the Boot disk into the drive and turn the power back on. Press the Enter key at the system boot prompt. When prompted to insert the Root disk, remove the Boot and insert the Root disk. The system is all booted by the emergency boot disk. Until the prompt #; 2. Mount the hard disk to the floppy disk with the command mount/dev/hd0root/mnt; 3. Copy the /bin/sh file from the floppy disk to the installed hard disk: cp/bin/sh/mnt /bin/sh; 4. Use the command umount/dev/hd0root to umount the hard disk from the floppy disk; 5. Use the haltsys to shut down the system and remove the root disk. The system can boot normally. 6. After the system boots normally. Enter the super user, and restore the system by changing the owner and group of the file /bin/sh to the bin defined by the system. The fourth system can boot, and can also handle daily affairs normally, but every time the computer is shut down, an error message will appear on the main console screen: /etc/initscript:/etc/uadmin:not found, then the system freezes, resulting in The system cannot be shut down normally, so each time the system needs to clean up the file system at startup, it not only wastes time, but also can seriously damage the file system, causing the system to crash. Analysis: The system file /etc/uadmin is missing or corrupted. Solution: 1. After the system boots and cleans up the file system, register with the superuser root (in single-user mode); 2. At the superuser prompt #, use the mount/dev/fd0135ds18/mnt command to root Disk is installed on the hard disk; 3. Copy the /etc/uadmin file from the floppy disk to the installed hard disk: cp/mnt/etc/uadmin/etc/uad min; 4. Use the command mount/dev/fd0135ds18/mnt The floppy disk is removed from the hard disk, and then the root disk is removed. 5. Change the owner and group of the file /etc/uadmin to the bin defined by the system. At this point, the system can be shut down normally. Fault 5 After the machine is powered up, type the Enter key at the system boot prompt. When the first screen is refreshed, the following message appears on the last line of the second screen: Kernel: I/o bufs=600k, and the system hangs. After the machine is powered on, type the Enter key at the system boot prompt. When the first screen is refreshed, the following message appears on the last line of the second screen: Kernel: I/o bufs=600k, and the system hangs. Analysis: This indicates that the system's /etc/init file is missing. Because the init program starts executing at the final stage of core initialization, its process number (pid) is 1. The process starts the processes listed in the /etc/inittab file according to certain rules, and guides the system to the specified run level. It first reads the initdefault entry in the /etc/init tab. When all processes are created successfully, init enters the loop wait. Init is mainly used to open the console /etc/console, check the consistency of the file system, and execute /etc/rc to make the necessary settings. Init starts the shell in single-user mode, and runs the shells /etc/brc, /etc/bchk in multi-user mode and starts /et c/rc. In addition, it also calls /etc/getty to generate a getty process for each terminal to complete the user registration process after reading the user registration name. If the /etc/init file is corrupted, the new process cannot be created, causing the system to hang. Solution: 1. Insert the Boot disk into the drive and re-power the machine. At this point, boot from the Boot disk, press the Enter key at the system boot prompt, and then remove the Boot disk and the Root disk when prompted to insert the Root disk. Insert, so that the system is all booted from the emergency boot disk until the prompt #; 2. Mount the hard disk to the floppy disk with the command mount/dev/hd0root/mnt; 3. Copy the /etc/init file from the floppy disk to the installed On the hard disk: cp /etc /init /mnt /etc /init; 4. Use the command umount /dev /hd0root to umount the hard disk from the floppy disk; 5. use the haltsys closed system to remove the root disk, the system has Can be booted normally; 6. After the system boots normally, enter the super user, and change the owner and group of the /etc/init file to the bin defined by the system.