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System Administration Guide: Basic Administration

Interactively Checking and Repairing a UFS File System

You might need to interactively check file systems in the following instances:

When an in-use file system develops inconsistencies, error messages might be displayed in the console window or the system might crash.

Before using the fsck command, you might want to refer to Syntax and Options for the fsck Command and “Resolving UFS File System Inconsistencies (Tasks)” in System Administration Guide: Advanced Administration for more information.

How to See If a File System Needs Checking

  1. Become superuser or assume an equivalent role.

  2. Unmount the file system if it is mounted.


    # umount /mount-point

  3. Check the file system.


    # fsck -m /dev/rdsk/device-name

    The state flag in the superblock of the file system you specify is checked to see whether the file system is clean or requires checking.

    If you omit the device argument, all the UFS file systems listed in the /etc/vfstab file with a fsck pass value greater than 0 are checked.

Example—Seeing If a File System Needs Checking

The following example shows that the file system needs checking.


# fsck -m /dev/rdsk/c0t0d0s6
** /dev/rdsk/c0t0d0s6
ufs fsck: sanity check: /dev/rdsk/c0t0d0s6 needs checking

How to Check File Systems Interactively

  1. Become superuser or assume an equivalent role.

  2. Unmount the local file systems except root (/) and /usr.


    # umountall -l

  3. Check the file systems.


    # fsck

    All file systems in the /etc/vfstab file with entries in the fsck pass field greater than 0 are checked. You can also specify the mount point directory or /dev/rdsk/device-name as arguments to the fsck command. Any inconsistency messages are displayed.

    For information about how to respond to the error message prompts while interactively checking one or more UFS file systems, see “Resolving UFS File System Inconsistencies (Tasks)” in System Administration Guide: Advanced Administration.

    Caution – Caution –

    Running the fsck command on a mounted file system might cause a system to crash if the fsck command makes any changes, unless stated otherwise, such as running the fsck command in single-user mode to repair a file system.

  4. If you corrected any errors, type fsck and press Return.

    The fsck command might be unable to fix all errors in one execution. If you see the message FILE SYSTEM STATE NOT SET TO OKAY, run the command again. If that does not work, see Fixing a UFS File System That the fsck Command Cannot Repair.

  5. Rename and move any files put in the lost+found directory.

    Individual files put in the lost+found directory by the fsck command are renamed with their inode numbers. If possible, rename the files and move them where they belong. You might be able to use the grep command to match phrases with individual files and the file command to identify file types. When whole directories are put into the lost+found directory, it is easier to figure out where they belong and to move them back.

Example—Checking File Systems Interactively

The following example shows how to check the /dev/rdsk/c0t0d0s6 file system and corrects the incorrect block count.


# fsck /dev/rdsk/c0t0d0s6
checkfilesys: /dev/rdsk/c0t0d0s6
** Phase 1 - Check Block and Sizes
INCORRECT BLOCK COUNT I=2529 (6 should be 2)
CORRECT? y

** Phase 2 - Check Pathnames
** Phase 3 - Check Connectivity
** Phase 4 - Check Reference Counts
** Phase 5 - Cylinder Groups
929 files, 8928 used, 2851 free (75 frags, 347 blocks, 0.6%
fragmentation)
/dev/rdsk/c0t0d0s6 FILE SYSTEM STATE SET TO OKAY
 
***** FILE SYSTEM WAS MODIFIED *****

Preening UFS File Systems

The fsck -o p command (p is for preen) checks UFS file systems and automatically fixes the problems that normally result from an unexpected system shutdown. This command exits immediately if it encounters a problem that requires operator intervention. This command also permits parallel checking of file systems.

You can run the fsck -o p command to preen the file systems after an unclean shutdown. In this mode, the fsck command does not look at the clean flag and does a full check. These actions are a subset of the actions that the fsck command takes when it runs interactively.

How to Preen a UFS File System

  1. Become superuser or assume an equivalent role.

  2. Unmount the UFS file system.


    # umount /mount-point

  3. Check the UFS file system with the preen option.


    # fsck -o p /dev/rdsk/device-name

    You can preen individual file systems by using /mount-point or /dev/rdsk/device-name as arguments to the fsck command.

Example—Preening a UFS File System

The following example shows how to preen the /usr file system.


# fsck -o p /usr

Fixing a UFS File System That the fsck Command Cannot Repair

Sometimes, you need to run the fsck command a few times to fix a file system because problems corrected on one pass might uncover other problems not found in earlier passes. The fsck command does not keep running until it comes up clean, so you must rerun it manually.

Pay attention to the information displayed by the fsck command. This information might help you fix the problem. For example, the messages might point to a damaged directory. If you delete the directory, you might find that the fsck command runs cleanly.

If the fsck command still cannot repair the file system, you can try to use the fsdb, ff, clri, and ncheck commands to figure out and fix what is wrong. For information about how to use these commands, see fsdb(1M), ff(1M), clri(1M), and ncheck(1M). You might, ultimately, need to re-create the file system and restore its contents from backup media.

For information about restoring complete file systems, see Chapter 49, Restoring Files and File Systems (Tasks).

If you cannot fully repair a file system but you can mount it read-only, try using the cp, tar, or cpio commands to retrieve all or part of the data from the file system.

If hardware disk errors are causing the problem, you might need to reformat and divide the disk into slices again before re-creating and restoring file systems. Hardware errors usually display the same error again and again across different commands. The format command tries to work around bad blocks on the disk. If the disk is too severely damaged, however, the problems might persist, even after reformatting. For information about using the format command, see format(1M). For information about installing a new disk, see Chapter 34, SPARC: Adding a Disk (Tasks) or Chapter 35, x86: Adding a Disk (Tasks).