tar and cpio Commands

Because they use a nonbinary format, the tar and cpio commands are the only utilities to successfully interchange data between SVR4 implementations. Other backup utilities, such as ufsdump and dd, are unique to the vendor and are not guaranteed to work successfully from one SVR4 implementation to another.

The tar command is unchanged in this release; it accepts the same options and command syntax as the SunOS release 4 command. However, since the device naming scheme has changed in the SunOS release 5.7 software, the tarfile (or device) argument is affected. When using the -f function modifier, specify the device argument as /dev/rmt/unit, where unit is a tape drive number and density. Table 9-16 shows the tape drive density characters in tape device names.

Table 9-16 Tape Drive Density Characters in Tape Device Names

Density	Description
Null	Default "preferred" (highest) density
l	Low
m	Medium
h	High
c	Compressed
u	Ultra

The tar command no longer uses /dev/rmt8 as its default output device. When the -f modifier is not used and the TAPE environment variable is not set, the tar command uses the defaults set in the /etc/default/tar file.

The SunOS release 5.7 cpio command supports the SunOS release 4 options and command syntax. cpio has been expanded to include many new options, as listed in Table 9-17.

Table 9-17 Additional cpio Options

Option	Command Available With Option	Description
-A	cpio -o	Appends files to an archive.
-k	cpio -i	Attempts to skip corrupt file headers and I/O errors encountered. This option lets you copy files from a medium that is corrupted or out of sequence.
-L	cpio -o or cpio -p	Follows symbolic links.
-V	cpio -i, cpio -o, or cpio -p	Special verbose. Prints a dot for each file read or written. This option assures you that cpio is working, without printing all file names.
-C bufsize	cpio -i or cpio -o	Blocks I/O bufsize bytes to the record, where bufsize is a positive integer. When neither -C nor -B is specified, the default buffer size is 512 bytes.
-E filename	cpio -i	Specifies and inputs file containing a list of file names to be extracted from the archive.
-H header	cpio -i or cpio -o	Reads or writes header information in header format. header can be one of: bar (read only), crc, CRC, odc, tar, TAR, ustar, or USTAR.
-I filename	cpio -i	Reads filename as an input archive.
-M message	cpio -i -I filename or cpio -o -O filename	Defines a message to use when switching media.
-O filename	cpio -o	Directs the output to filename.
-R userid	cpio -i or cpio -p	Reassigns ownership and group information for each file to userid.

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Note -

cpio requires one of three mutually exclusive options to specify the action to take: -i (copy in), -o (copy out), or -p (pass).

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