You might need to interactively check a file system when you are unable to mount it or when the file system develops inconsistencies.
When a file system in use develops inconsistencies, error messages are displayed on the console window or on the system message file, or the system might crash. For example, the system messages file, /var/adm/messages, might include messages such as:
Sep 5 13:42:40 hostname ufs: [ID 879645 kern.notice] NOTICE: /: unexpected free inode 630916, run fsck(1M)
hostname is the system which is reporting the error.
Consider the following aspects when running the fsck command to check UFS file systems:
A file system must be inactive in order to be checked. File system changes waiting to be flushed to disk or file system changes that occur during fsck checking process can be interpreted as file system corruption. These issues might not be a reliable indication of a problem.
A file system must be inactive in order to be repaired. File system changes waiting to be flushed to disk or file system changes that occur during the fsck repairing process might cause the file system corruption. This might also cause the system to crash.
Unmount a file system before you use fsck on that file system. Unmounting the file system ensures the data structures in it are consistent.
If a UFS file system runs out of space, you can see the following message in the /var/adm/messages file.
file system full
For more information about troubleshooting file system issues, see Chapter 3, Troubleshooting File System Problems in Troubleshooting System Administration Issues in Oracle Solaris 11.3.