ChorusOS 4.0 File System Administration Guide

Chapter 2 How to Configure the System Image

This chapter explains how to create a system image with support for file systems and related hardware.

Note -

Before attempting to configure any of the features and tunables described below, check that they are supported by your ChorusOS system. Consult the appropriate document in the ChorusOS 4.0 Target Family Documentation Collection to determine which features and tunables your version supports.

For descriptions of available features and tunables, read the appropriate sections of the ChorusOS 4.0 Introduction. For more details concerning features, see ChorusOS man pages section 5FEA: ChorusOS Features.

2.1 What ChorusOS Systems Support

This section reviews the file systems and related media supported for the ChorusOS 4.0 product. As stated in the note above, support for specific ChorusOS file systems and hardware devices depends on the target family.

2.1.1 Supported Media

The ChorusOS 4.0 product supports the following hardware, although not necessarily for all target platforms:

Flash memory: Flash device support is implemented using Flite 1.2. Flash support allows you to use only MS-DOS file systems on supported flash devices.
IDE hard disk drives: Supported hard disk drives must be connected to an IDE, ST506 or ESDI compatible disk controller.
RAM disk memory: RAM disk support allows you to create disk-like entities and use file systems in random-access memory.
SCSI hard disk drives: Selected SCSI hard disk drives and SCSI-PCI I/O processors of the NCR53C8xx family are supported.

ChorusOS 4.0 requires that you use special device driver files in order to read from and write to these devices. See "2.3 Required Special Device Driver Files" and special(7S) for details.

2.1.2 Supported File Systems

The ChorusOS 4.0 product supports the following file systems, although not necessarily for all target platforms:

Network File System (NFS): NFS is the standard among UNIX operating systems for sharing file systems over the network. ChorusOS systems can support both NFS client access to shared file systems and NFS server capabilities to share local file systems with other systems on the network.
File Allocation Table (FAT) File System: Also known as the MS-DOS file system, this supports file allocation tables with 12, 16 or 32-bit entries, making it possible to support long file names.
UNIX File System (UFS): Also known as the Fast File System, this supports long file names and links, and is the required type for file systems exported through NFS.
Swap File System: The ChorusOS 4.0 product also supports the use of a swap partition on supported local hardware devices.

The following table summarizes which file systems are supported for which media.

Table 2-1 File System Support By Media


	MS-DOS	UFS	Swap
Flash	X
IDE	X	X	X
RAM disk	X	X
SCSI	X	X	X

2.2 How to Add Support for File Systems and Related Hardware

Adding Support Using the Graphical User Interface Tool

To configure your system image with support for file systems and related hardware through the ews graphical user interface, follow the procedure below.

Open your system image configuration in ews:

host% cd build_dir
host% ews conf/ChorusOS.xml &

Use the hints in the following tables to set features and tunables for the file system support needed.

The following table lists the feature and tunable settings required for your ChorusOS system to support the media on which you use file systems.

Table 2-2 Media Support


To include support for...	Set...	Comments
Flash memory	FLASH=true	Flash memory supports only FAT (MS-DOS) file systems.
IDE hard disk drives	IDE_DISK=true	Enables support for hard disk drives connected to compatible IDE, ST506 and ESDI controllers.
RAM disk memory	RAM_DISK=true iom.ramdisk`X`.size=`size_in_hex` iom.ramdisk.sizeMax= `max_RAM_disk_size`	iom.ramdisk`X`.size, where `X` is a hexadecimal digit `0`, `1`, `2`, ..., `d`, `e`, `f`, takes a size in the same hexadecimal format as the value for iom.ramdisk.sizeMax. For example, if you want to have one 4MB RAM disk use iom.ramdisk0.size= 0x40000.
SCSI hard disk drives	SCSI_DISK=true	Enables support for SCSI-PCI I/O processors of the NCR53C8xx family.

The following table summarizes the feature and tunable settings required for your ChorusOS system to support specific file systems.

Table 2-3 File System Support


To include support for...	Set...	Comments
FAT (MS-DOS) file systems	MSDOSFS=true iom.nbuf=32 (at least)
NFS client capability (for mounting NFS file systems)	NFS_CLIENT=true iom.nbuf=8 (at least)
NFS server capability (for exporting file systems)	NFS_CLIENT=true NFS_SERVER=true iom.kmemsize=0x80000 (at least) iom.nbuf=8 (at least)	The ChorusOS system can export only local UFS file systems through NFS. MS-DOS file systems cannot be exported through NFS.
Swap file system	FS_MAPPER=true ON_DEMAND_PAGING= true (except for PowerPC target family architectures)	Swap may only be used on local media. Only one swap device may be used. Swap is only available in the VM memory model, where VIRTUAL_ADDRESS_SPACE =true.
UNIX (UFS) file systems	UFS=true iom.nbuf=8 (at least)	UFS file systems cannot be used on flash media.

The iom.nbuf tunable sets the number of buffer cache entries; the standard buffered entries used for input and output. The larger the value, the larger the cache available. The iom.nbuf tunable influences the amount of RAM used by the system.

The iom.kmemsize tunable sets the amount of memory available to the kernel.

Save your changes to the system image configuration.

Build the system image.

Adding Support Using Command-Line Tools

To configure your system image with support for file systems and related hardware through the configurator(1CC) command-line interface, follow the procedure below.

Change to the directory where you build system images:
host% cd build_dir

Use the hints in the tables above (see Step 2) to set features and tunables for the file system support needed.

configurator(1CC) commands to set features and tunables take the form:
host% configurator -c conf/ChorusOS.xml -set feature | tunable=value

Build the system image to include the modifications you have made:
host% make system_image_name

2.3 Required Special Device Driver Files

This section reviews the special device driver files required for file system support.

If your target is an NFS client only (all its files are physically located on another system, such as the host workstation), you can skip this section.

2.3.1 What Special Files Are

The ChorusOS system requires you to use special(7S) device driver files to access the hardware devices where file systems reside. This means that disk labelling and other operations on uninitialized and unmounted file systems must be done using special files.

Each disk partition corresponds to at least one special file. Unless you plan to use a raw partition directly, without a file system, you must be able to access each partition in both block (buffered) mode and raw (character) mode, so you must create not just one special file per partition, but two. Each special file:

Refers to either a block or a raw device. Block devices are used by file systems. Raw devices are used primarily for file system administration.
Has a major number. Major numbers are used by the system to select the corresponding device driver when several devices are configured. Major numbers are the same for all devices managed by a given device driver and a given access method (raw or block). For example, all devices corresponding to hard disk partitions using raw mode have the same major number.
Has a minor number. Minor numbers are not used directly by the system, but by the selected device driver. Minor numbers are different for each partition on a device. Their scope is limited to the device described by the major number, so special files with different major numbers may share the same minor number. One minor number corresponds to one partition.

2.3.2 Naming Conventions for Special Files

Special files normally reside in the /dev directory, which is mounted at boot time. By convention, special file names follow the form /dev/rsuffix for raw (character) mode and /dev/suffix for buffered (block) mode.

The suffix is made up of:

A string of letters referring to the device driver name, such as sd for a SCSI disk, rd for a RAM disk, hd for an IDE disk or flash for flash,
Followed by a digit representing the disk unit number, such as 0, 1, 2 and so forth (except for special files not related to file systems, such as tty device files),
Terminated by a single letter referring to the partition, such as a, b, ... h.

Caution -

Special care must be taken with partition c. Partition c represents the whole disk and therefore must not be used to support a file system.

As file systems are based on BSD 4.4 as implemented in FreeBSD 2.2.7, the same limitations found in FreeBSD 2.2.7 apply to ChorusOS file system management. According to limitations imposed by FreeBSD, a disk can be divided into a maximum of eight different partitions for IDE and SCSI devices, two partitions for RAM and flash devices. Partitions can be left undefined. Partitions are named using a single character in the range from a to h, each letter corresponding to one of the eight partitions for IDE and SCSI devices. For RAM and flash devices, only partitions a and c are available.

2.4 How to Create Special Files

You create special files using mknod(1M) on the ChorusOS system. Generally, you create the special files you need at boot time by including commands in the system initialization file, sysadm.ini(4CC).

Note -

Unlike earlier releases that used special device driver files created on the host, the ChorusOS 4.0 product only lets you create special files on the target.

Previous releases allowed you to create special files on the host because no /dev directory was available at boot time. As the ChorusOS 4.0 product mounts a /dev directory at boot time, it is no longer necessary to create special files on the host.

Creating Special Files at Boot Time

To create special files at boot time using the sysadm.ini(4CC) file embedded in the system image, follow the procedure below:

Change to the directory containing sysadm.ini:
host% cd build_dir/conf

Include commands of the following form in sysadm.ini using the C_INIT(1M) built-in command mknod(1M):

mknod /dev/name [b|c] maj_nbr min_nbr

where name follows the pattern described above in "2.3.2 Naming Conventions for Special Files", b represents a buffered (block) device, c represents a character (raw) device, maj_nbr is the major number of the device and min_nbr is the minor number of the partition on the device. The following table lists memory devices by major number:

Major Number	Device	Mode
3	ISA/IDE disk	character (raw)
4	ISA/IDE disk	block (buffered)
7	Flash device	character (raw)
8	Flash device	block (buffered)
9	SCSI disk	character (raw)
10	SCSI disk	block (buffered)
13	RAM disk	character (raw)
14	RAM disk	block (buffered)

Note that RAM disk devices used for memory banks conventionally have major numbers 11 and 12 and are used internally by the system to make the contents of the memory banks, including the system image, available for use at boot time.

Build the system image to include modifications to sysadm.ini:
host% cd .. host% make system_image_name

Creating Special Files Manually

To create special files manually on a running ChorusOS target system:

Run commands on the target of the type:

host% rsh target mknod /dev/name [b|c] maj_nbr min_nbr

Where name follows the pattern described above in "2.3.2 Naming Conventions for Special Files", b represents a buffered (block) device, c represents a character (raw) device, maj_nbr is the major number of the device and min_nbr is the minor number of the partition on the device.