File systems for system WPARs

System WPARs have their own file systems similar to stand-alone AIX®.

System WPARs can be created with local file system spaces, which are constructed from isolated sections of the file system space for the global environment or with a WPAR owned root volume group.

When the system WPAR isolates the file system spaces, each file system is owned and managed by the global environment. For a WPAR owned root volume group, dedicated storage devices must be allocated to the WPAR and each file system is owned and managed by the WPAR.

Global isolated file system spaces

The default location for the file system spaces is in the /wpars directory of the global environment. The initial process for each WPAR is moved to the correct path in the global file system using the chroot command. All processes run within the WPAR and appear in the base directory for the WPAR. For example, users in a WPAR would see the /wpars/part1/usr directory as the /usr directory.

The file system configuration for a WPAR is specified when the WPAR is created. You can either use the system defaults or customize each file system. Some of the file systems in a system WPAR are local to the partition while others can be shared with the global environment.

The following JFS2 file systems are created with inline logs and populated similar to a stand-alone AIX system with the following sizes:

/ (64 MB)
/tmp (96 MB)
/var (128 MB)
/home (32 MB)

Note: The initial sizes of these file systems could change depending on the system requirements and storage characteristics.

The following JFS2 file systems are shared from the global environment using namefs mounts with the following permissions:

/usr (read-only permissions)
/opt (read-only permissions)
/proc (read/write permissions)

You can specify the use of a flat file system structure for part or all of a WPAR namespace by specifying that one or more directories can be local to a parent directory. This structure means that no distinct file system is created for the parent directory. The sizes of the file systems or directories to be populated in the WPAR must be large enough to hold the files for that partition. This structure simplifies the number of file systems to manage for a partition, but it loses the granularity of control over user files populating the file system. The flat file system structure might be a viable option for servers running in the WPAR that do not offer system login privileges to users.

File systems in a rootvg WPAR

When a system WPAR is created with its own root volume group by using the mkwpar command with the –D flag and specifying the disk name devname=hdisk name and the rootvg=yes option, the root file systems are created in a separate volume group that is owned and managed by the WPAR. For example, two disks can be allocated for the root volume group by using these options -D devname=hdisk5 rootvg=yes -D devname=hdisk6 rootvg=yes. The following JFS2 file systems are created within the WPAR-owned root volume group with inline logs, and populated similar to a stand-alone AIX operating system:

/
/admin
/home
/tmp
/var

Note: The initial sizes of these file systems can change depending on the system requirements and storage characteristics.

If a non-shared system WPAR is created that owns the root volume group, the /usr file system and /opt file system are created and populated within the WPAR owned root volume group. Versioned WPARs always have non-shared /usr and /opt file systems. Otherwise, the /usr file system and /opt file system are shared from the global environment by using namefs mounts.

Note: The logical volume names used within a rootvg WPAR are the same as those typically used on an AIX system. For example, /dev/hd4 would be the logical volume name for the root / file system and /dev/hd11admin for the /admin file system.

The WPAR administrator can change the file system characteristics of any file system that resides within the WPAR-owned root volume group.

File systems in a system copy WPAR

When a WPAR is created as a system copy from an AIX system or AIX system image, the file systems included in the WPAR are based on the file systems in the root volume group of the source.

If the source for creating the WPAR is an AIX system backup image, the file systems included by default in the system copy WPAR are the file systems that are listed in the image.data file from the system backup image. The system administrator can override the file system settings by using the mkwpar command-line option (-M) or specification files, but the administrator has the responsibility of ensuring that the resulting file system settings are sufficient to contain the files from the backup image.

If the source for creating the WPAR is a running AIX system rather than a system backup image, the default file systems for the WPAR are the mounted file systems from the rootvg of the global system, with the following exceptions:

File systems associated with WPARs are not included by default. You can override this setting by using the -T preserve_wpars=yes option to the mkwpar command or by setting preserve_wpars=yes in a copy_controls stanza of a WPAR specification file.
The /usr and /opt file systems from the global system are not copied if the WPAR is created as a shared WPAR. If the WPAR is created with the -l option or if the privateusr=yes attribute is set in the general stanza of a WPAR specification file, the /usr and /opt file systems are copied into the WPAR. Otherwise, the WPAR mounts the /usr and /opt file systems in read-only mode from the global system.

A system copy WPAR can be created as a rootvg WPAR.