Allocating a file system for the root file system

In open systems analogous to z/OS UNIX, allocation might be called making the file system. The root file system must be allocated by a user who has an UID of 0, indicating superuser authority. To create file systems, a security product that supports the SAF calls made during the system processing must be running.

Example: This example shows a sample job that defines the zFS root file system. Two steps are required. The file system must first be defined and then formatted. The allocation specified in this sample does not reflect the amount of space needed for the root file system. For exact size information, consult z/OS Program Directory. Later, during customization, put the specified aggregate name of the root file system in the ROOT statement in the BPXPRMxx member. In this example the owner of the file system is assigned to UID (-owner 0) and the file system permissions are 0755 (-perms o755).

//USERIDA JOB ,'Compatibility Mode',
// CLASS=A,MSGCLASS=X,MSGLEVEL=(1,1)
//DEFINE EXEC PGM=IDCAMS
//SYSPRINT DD SYSOUT=H
//SYSUDUMP DD SYSOUT=H
//AMSDUMP DD SYSOUT=H
//DASD0 DD DISP=OLD,UNIT=3390,VOL=SER=PRV000
//SYSIN DD *
    DEFINE CLUSTER (NAME(OMVS.ROOT) -
           VOLUMES(PRV000) -
           LINEAR CYL(40 1) SHAREOPTIONS(3))
/*
//CREATE EXEC PGM=IOEAGFMT,REGION=0M,
// PARM=('-aggregate OMVS.ROOT -compat -owner 0 -perms o755')
//SYSPRINT DD SYSOUT=H
//STDOUT DD SYSOUT=H
//STDERR DD SYSOUT=H
//SYSUDUMP DD SYSOUT=H
//CEEDUMP DD SYSOUT=H
//*

Example: This example shows a sample job that defines the root file system in an MKFS DD statement for a HFS file system. The allocation specified in this sample does not reflect the amount of space needed for the root file system. For exact size information, consult z/OS Program Directory. When you specify space for the file system, you must provide a nonzero value for the directory space parameter, which is not used. Or you can specify DSORG=PO to create a data set with partitioned organization. The DSNAME is in the ROOT statement. Later, during customization, put the DSNAME of the root file system in the ROOT statement in the BPXPRMxx member.

//OMVSXX    JOB
//STEP03 EXEC  PGM=IEFBR14
//MKFS   DD   DSNAME=OMVS.ROOT,
//            SPACE=(CYL,(40,1,1)),DCB=(DSORG=PO),
//            DSNTYPE=HFS,
//            DISP=(NEW,CATLG,DELETE),
//            STORCLAS=STANDARD

Other MVS™ data sets can reside in available parts of the volume containing the file system. You can also use the ISPF shell, or the TSO/E ALLOCATE command to create a file system.

See the following topics:

To learn more about creating zFS file systems, see the section on creating and managing zFS file systems using compatibility mode aggregates in z/OS Distributed File Service zFS Administration.
For JOB, EXEC, and DD statements, see z/OS MVS JCL Reference.
For reference information about BPXPRMxx, go to z/OS MVS Initialization and Tuning Reference. For guidance information, see Customizing the BPXPRMxx member of SYS1.PARMLIB.
To learn more about setting up the root file system structure, see Structure of the z/OS UNIX file system.

File systems can be allocated by systems other than the one on which the data set will be used, as long as the allocating system has the correct level of DFSMS. The system where the file system will be used must share the catalog with the allocating system or have a catalog entry for the same file system name.