System Administration Guide: Devices and File Systems

Commands for Copying File Systems

When you need to back up and restore complete UFS file systems, use the ufsdump and ufsrestore commands described in Chapter 28, UFS Backup and Restore Commands (Reference). When you want to copy or move individual files, portions of file systems, or complete file systems, you can use the procedures described in this chapter instead of the ufsdump and ufsrestore commands.

The following table describes when to use the various backup commands.

Table 29–1 When to Use Various Backup Commands


Task	Command	For More Information
Back up UFS file systems to tape.	`ufsdump`	How to Back Up a UFS File System to Tape
Create a file system snapshot.	`fssnap`	Chapter 26, Using UFS Snapshots (Tasks)
Restore UFS file systems from tape.	`ufsrestore`	How to Restore a Complete UFS File System
Transport files to other systems.	`pax`, `tar`, or `cpio`	Copying Files and File Systems to Tape
Copy files or file systems between disks.	`dd`	How to Copy a Disk (`dd`)
Copy files to diskette.	`tar`	How to Copy Files to a Single Formatted Diskette (`tar`)

The following table describes various backup and restore commands.

Table 29–2 Summary of Various Backup Commands


Command Name	Aware of File System Boundaries?	Supports Multiple Volume Backups?	Physical or Logical Copy?
`volcopy`	Yes	Yes	Physical
`tar`	No	No	Logical
`cpio`	No	Yes	Logical
`pax`	Yes	Yes	Logical
`dd`	Yes	No	Physical
`ufsdump/ufsrestore`	Yes	Yes	Logical
`fssnap`	N/A	N/A	Logical

The following table describes the advantages and disadvantages of some of these commands.

Table 29–3 Advantages and Disadvantages of tar, pax, and cpio Commands


Command	Function	Advantages	Disadvantages
`tar`	Use to copy files and directory subtrees to a single tape.	Available on most UNIX operating systems Public domain versions are readily available	Is not aware of file system boundaries Length of full path name cannot exceed 255 characters Cannot be used to create multiple tape volumes
`pax`	Use to copy files, special files, or file systems that require multiple tape volumes. Or, use when you want to copy files to and from POSIX-compliant systems.	Better portability than the `tar` or `cpio` commands for POSIX-compliant systems Multiple vendor support	Same disadvantages as the `tar` command, except that the `pax` command can create multiple tape volumes.
`cpio`	Use to copy files, special files, or file systems that require multiple tape volumes. Or, use when you want to copy files from systems running current Solaris releases systems to systems running SunOS 4.0/4.1 releases.	Packs data onto tape more efficiently than the `tar` command Skips over any bad spots in a tape when restoring Provides options for writing files with different header formats, such as ( `tar`, `ustar`, `crc`, `odc`, `bar`), for portability between different system types Creates multiple tape volumes	The command syntax is more difficult than the `tar` or `pax` commands.

The following sections describes step-by-step instructions and examples of how to use these commands.