HOWTO: Multi Disk System Tuning

• Index
• Introduction
• Structure
• Drive Technologies
• File System Structure
• File Systems
• Technologies
• Other Operating Systems
• Clusters
• Mount Points
• Considerations and Dimensioning
• Disk Layout
• Implementation
• Maintenance
• Advanced Issues
• Troubleshooting
• Further Information
• Getting Help
• Concluding Remarks
• Questions and Answers
• Bits and Pieces
• Appendix A: Partitioning Layout Table: Mounting and Linking
• Appendix B: Partitioning Layout Table: Numbering and Sizing
• Appendix C: Partitioning Layout Table: Partition Placement
• Appendix D: Example: Multipurpose Server
• Appendix E: Example: Mounting and Linking
• Appendix F: Example: Numbering and Sizing
• Appendix G: Example: Partition Placement
• Appendix H: Example II
• Appendix I: Example III: SPARC Solaris
• Appendix J: Example IV: Server with 4 Drives
• Appendix K: Example V: Dual Drive System
• Appendix L: Example VI: Single Drive System
• Appendix M: Disk System Documenter

15. Troubleshooting

Much can go wrong and this is the start of a growing list of symptoms, problems and solutions:

15.1 During Installation

Locating Disks

Symptoms

Cannot find disk

Problem

How to find what drive letter corresponds to what disk/partition

Solution

Remember Linux does not use drive letters but device names. More information can be found in Drive names.

Symptoms

Cannot partition disk

Problem

Most likely wrong input to the command line for fdisk or similar tool.

Solution

Remember to use /dev/hda rather than just hda. Also do not use numbers behind hda, those indicate partitions.

Formatting

Symptoms

Cannot format disk.

Problem

Strictly speaking you format partitions not disks.

Solution

Make sure you add the partition number after the device name of the disk, for instance /dev/hda1 to the command line.

15.2 During Booting

Booting fails

Symptoms

Number keep scrolling up the screen.

Problem

Possibly corrupt disk.

Solution

Try another disk, you might have to reinstall. Check for loose cables and possible data corruption.

Symptoms

Get LI and then it hangs.

Problem

You use LILO to load Linux but LILO cannot find your root.

Solution

Read the LILO HOWTO.

Symptoms

Kernel panics, something about missing root file system.

Problem

The kernel does not know where the root partition is.

Solution

Use rdev or (if applicable) LILO to add information to the kernel image where your root is.

Getting into Single User Mode

Symptoms

System boots but get into a root shell in single user mode.

Problem

Something went wrong in the later stages of booting and the system has come far enough to let you open a shell to repair the system.

Solution

Locate the problems from the boot log. Note that file system can be in read-only mode. Remount read-write if you have to. Often the reason is that the /etc/fstab contained an entry that was mismapped such as trying to mount a swap partition as your normal file space.

15.3 During Running

Swap

Symptoms

Short on memory

Problem

Swap space is not available

Solution

Type free and check the output. If you get

             total       used       free     shared    buffers     cached
Mem:         46920      30136      16784       7480      11788       5764
-/+ buffers/cache:      12584      34336
Swap:       128484       9176     119308

then system is running normal. If the line with Swap: contains zeros you have either not mounted the swap space (partition or swap file) (see swapon(8)) or not formatted the swap space (see mkswap(8)).

Partitions

Symptoms

No room amidst plenty 1

Problem

Partitionitis:Underdimensioned partition sizes has caused overflow in some areas

Solution

Examine your partition usage using df(1) and locate problem areas. Normally the problem can be solved by removing old junk but you might have to repartition your system, see section Repartitioning.

Symptoms

No room amidst plenty 2

Problem

Running out of i-nodes has caused overflow in some ares, often in areas with many small files such as news spool.

Solution

Examine your partition usage using df -i and locate problem areas. Normally the problem is solved by reformatting using a higher number of i-nodes, see mkfs(8) and related man pages.