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chpt(8)								       chpt(8)

Name
       chpt - change a disk partition table

Syntax
       /etc/chpt  [  -a	 ]  [  -d  ] [ -q ] [ -v ] [ [ -px offset size ] ... ]
       device

Description
       The command lets you alter the partition sizes of a disk.  You can  use
       the  command  to	 tailor your system disks and their partitions to suit
       your system's individual needs.

       If you want to create a file system on a partition that has been	 modi‐
       fied, you must use

       The standard procedure to change a partition table is:

       1. Look at the current partition table by using the -q option.

       2. If  a	 file  system does not exist on the a partition, create one by
	  using the command.

	  If a file system exists on the a partition but does  not  contain  a
	  partition table in its superblock, copy the partition table from the
	  driver to the superblock by using the command with the -a option.

       3. Change the partition offsets and sizes by using the -px option.  You
	  can change all the partitions for one disk on one command line.

       The  device  must  be  either  the  a or c partition of the raw device,
       depending upon where the file system resides.  For example, if the file
       system  resides	in  the	 a  partition of an RM05 in drive 0, device is
       rhp0a.

       A file system must exist on the a or c partition of the disk.   If  you
       do not have a file system there, create one by using the command.

Options
       -a    Copies the partition table in the device driver to the disk.

       -d    Copies the default partition table to the disk and to the current
	     partition table in the driver.  The default  partition  table  is
	     the table that was built with the disk driver.

       -q    Runs  the	command	 without modifying the partition tables.  This
	     prints the partition table of the specified disk.	It prints  the
	     default  partition	 table	in the driver if there is no partition
	     table on the disk.

       -v    Prints verbose messages showing the progress of the command.

       -px   Changes the parameters of one of the  partitions on the  disk  to
	     the  specified  offset and size.  The x argument is the partition
	     you are modifying (a, b, c, d, e, f, g, or h).  The Offset	 argu‐
	     ment  is  the  new beginning sector, and the size argument is the
	     new total number of sectors of the partition being modified.

Examples
       This example shows how to change the partition table on an RM05 disk in
       drive  1.  The commands in this example change the size of the h parti‐
       tion to include the g partition.	 Comments are in  parenthesis  to  the
       right of commands.
       % chpt -q /dev/rhp1a	(view partition table)
       /dev/rhp1a
       No partition table found in superblock...
       using default table from device driver.
       Current partition table:
       partition       bottom	    top	     size    overlap
	   a		    0	  15883	    15884    c
	   b		16416	  49855	    33440    c
	   c		    0	 500383	   500384    a,b,d,e,f,g,h
	   d	       341696	 357579	    15884    c,g
	   e	       358112	 414047	    55936    c,g
	   f	       414048	 500287	    86240    c,g
	   g	       341696	 500287	   158592    c,d,e,f
	   h		49856	 341201	   291346    c
       In  all	of the tables generated by the command, the bottom column con‐
       tains the offset (starting sector), the top column contains the	ending
       sector,	and the size column contains the number of sectors in the par‐
       tition.	The overlap column contains the other sectors  that  are  par‐
       tially or entirely included in the partition.
       % bc		   (basic calculator)
       500287-49856	   (top of g minus bottom of h)
       450431
       450431+1		   (add 1 because it is zero-based)
       450432		   (size of new h partition)

       In  the display of the example query, you can see that there is no par‐
       tition table in the superblock of the a partition.  If this is  because
       there  is  no file system in the a partition, run the command to create
       one.

       For this example, assume that there is a file system in the a partition
       of  the disk, but the file system does not contain a partition table in
       its superblock.	Therefore, run the command with the -a option to  copy
       the partition table in the driver to the superblock of the a partition.
       % chpt -a /dev/rhp1a	(add table to a partition)

       Now you have a partition table to change.  For example:
       % chpt -v -ph 49856 450432 /dev/rhp1c   (change h)
       /dev/rhp1c
       New partition table:
       partition       bottom  top     size    overlap
	   a		    0	15883	15884  c
	   b		16416	49855	33440  c
	   c		    0  500383  500384  a,b,d,e,f,g,h
	   d	       341696  357579	15884  c,g,h
	   e	       358112  414047	55936  c,g,h
	   f	       414048  500287	86240  c,g,h
	   g	       341696  500287  158592  c,d,e,f,h
	   h		49856  500287  450432  c,d,e,f,g

Caution
       Changing	 partition  tables  indiscriminately can result in the loss of
       large amounts of data.

       Check for file systems on all the partitions of the disk	 before	 using
       the  -p	option.	  If  a	 file  system  exists  whose  partition may be
       destroyed, copy it to a backup medium.  After you have changed the par‐
       titions, restore the backed up file system.

Restrictions
       You must have superuser privileges to use the command.

       You can not shrink or change the offset of a partition with a file sys‐
       tem mounted on it or with an open file descriptor on the entire	parti‐
       tion.

       You can not change the offset of the a partition.

See Also
       ioctl(2), disktab(5), fsck(8), mkfs(8), newfs(8)
       Guide to System Disk Maintenance

								       chpt(8)
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