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Help syntax to restore partition from ftp
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chpt(8) System Manager's Manual 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 pack. Using you can 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 modified, you must use The standard procedure to change a partition table is: 1. Look at the current partition table using the -q option. 2. If a file system does not exist on the a partition, create one 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 using the command with the -a option. 3. Change the partition offsets and sizes using the -px option. You can change all the partitions for one pack 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 pack. If you do not have a file system there, create one using Options -a Copies the partition table in the device driver to the disk pack. -d Copies the default partition table to the disk pack 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 without modifying the partition tables. This prints the partition table of the specified disk pack. It prints the default par- tition table in the driver if there is no partition table on the disk pack. -v Prints verbose messages showing the progress of -px Changes the parameters of partition x on the disk pack to the specified offset and size. x is the partition you are modifying (a, b, c, d, e, f, g, or h). Offset is the new beginning sector, and size is the new total number of sectors of the partition being modi- fied. Examples This example shows how to change the partition table on an RM05 disk pack in drive 1. The commands in this example change the the size of the h partition 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 bottom is the offset (starting sector), top is the ending sector, and size is the number of sectors in the partition. The overlap is the other sectors that are partially 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) % From the query, you can see that there is no partition 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 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. % chpt -v -ph 49856 450432 /dev/rhp1a (change h) /dev/rhp1a 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 losing 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 partitions, restore the backed up file system. Restrictions You must have superuser privileges to use You can not shrink or change the offset of a partition with a file system mounted on it or with an open file descriptor on the entire par- tition. 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)
