|
|
Coral8 5.5: Snapshot Queries with Live Updates
|
|
fscat_vxfs(1M) fscat_vxfs(1M) NAME
fscat_vxfs: fscat - cat a VxFS file system SYNOPSIS
output-file] offset] length] block_size] special DESCRIPTION
provides an interface to a VxFS snapshot file system, similar to that provided by invoked on the block or character special file of regular VxFS file systems. works when executed on the special device of any VxFS file system. On most VxFS file systems, the block or character special file for the file system provides access to a raw image of the file system to back up the file system to tape. On a snapshot file system, access to the corresponding block or character special file provides little useful information. provides a stream of bytes representing the file system snapshot. This datastream is written by default to standard output, although the output-file option can be used to specify another destination. The datastream on standard output can be processed several ways, such as in a pipeline, or written to a tape. By default, the output is a stream of bytes that starts at the beginning of the file system and continues to the last byte. On a snapshot file system, data is read from the file system using special ioctls on the mount point. On other VxFS file systems, data is read from the specified special file. Unless otherwise specified, data is written to standard output. All numbers entered as option arguments can have as a prefix to indicate octal, or as a prefix to indicate hexadecimal. A or can be appended to indicate the value is in 512-byte blocks, a or to indicate the value is in kilobytes, an or to indicate the value is in megabytes, or a or to indicate the value is in gigabytes. An appended letter can be separated from the number by a space, in which case the letter and number should be enclosed in a set of quotes. For example: All numbers entered as options must be in multiples of 512 bytes. For example, a value of 5713 as an offset is rejected. Options recognizes the following options: Specify the output block size, in bytes. block_size must be less than or equal to 1 megabyte. Specify the VxFS file system type. Specify an output file in which to write the datastream. Specify the transfer length, in bytes. A length of includes the remainder of the file system after the specified offset. Specify the starting offset in bytes. Operands recognizes the following operand: special Name of the special device from which the VxFS file system is accessed. Notes Snapshot file systems are only available with the HP OnLineJFS product. A snapshot file system cannot be written to. A snapshot file system exists only as long as it is mounted; once unmounted, the special file no longer contains a snapshot file system. When is run on a mounted VxFS snapshot, the content of free blocks (that is, blocks not allocated to any file or metadata) is undefined. The content of free blocks can change after additional data is written to the primary file system, but blocks associated with files always display the content they had when the snapshot was created. does not work with Storage Checkpoints. SEE ALSO
dd(1), fs_vxfs(4), vxfsio(7). fscat_vxfs(1M)
