fscat_vxfs

NAME

fscat_vxfs - cat a VxFS file system

SYNOPSIS

AVAILABILITY

VRTSvxfs

DESCRIPTION

fscat provides an interface to a VxFS snapshot file system similar to that provided by the dd command when dd is invoked on the block or character special file of a regular VxFS file system. fscat 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. fscat provides a stream of bytes representing the file system snapshot. The datastream is written by default to standard out, but you can specify a destination file using the -f output_file option.

The datastream on standard output can be processed in several ways, such as using a pipeline or writing to a tape.

By default, the output is a stream of bytes that starts at the beginning of the file system and goes to the end. 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 options can have 0 as a prefix to indicate octal, or a 0x prefix to indicate hexadecimal. A b or B can be appended to indicate the value is in 512-byte blocks, a k or K to indicate the value is in kilobytes, an m or M to indicate the value is in megabytes, a g or G to indicate the value is in gigabytes, or a t or T to indicate the value is in terabytes. An appended letter may be separated from the number by a space, in which case, enclose the letter and number in quotes. For example:

"512 b" 

All numbers entered as options must be in multiples of 512 bytes. For example, a value of 5713 as an offset is rejected.

NOTES

A snapshot file system cannot be written to. A snapshot file system exists only as long as it is mounted; after it is unmounted, the special file no longer contains a snapshot file system.

When fscat 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 (snapped) file system, but blocks associated with files will always display the content they had when the snapshot was created.

fscat does not work with Storage Checkpoints.

CLUSTER FILE SYSTEM ISSUES

The fscat command is not supported on cluster file systems.

OPTIONS

-b block_size

Specifies the output block size in bytes. block_size must be less than or equal to eight megabytes and must be a multiple of 1024 bytes.

-f output_file

Specifies an output file in which to write the datastream.

-F vxfs

Specifies the VxFS file system type.

-l length

Specifies the length in bytes. length must be a multiple of 1024 bytes. A length of 0 goes to the end of the file system.

-o offset

Specifies the starting offset in bytes. offset must be a multiple of 512 bytes.

SEE ALSO

dd(1), fsckptadm (1M), fs_vxfs (4), vxfsio (7)