Description
Iago is the Cedar disk formatting and maintenance program. It provides commands to prepare disks for operation in a Cedar system, to describe the machine on which it is running, and to effect some simple repairs when things break.
Iago can be invoked in two ways: by net booting Cedar or by booting Cedar with the 'l switch and answering 'y to the question "Do you want to use Iago?".
Once in Iago, it is only necessary to type a unique prefix followed by a separator, such as blank or carriage-return, to invoke any of the following commands. Many of the commands have their own prompters. Any time the program is expecting keyboard input, DEL will return you to the top level command interpreter. This is not an interrupt: it won't stop a long running command such as format.
Bare Machine Commands
Describe Machine
Provides info about the processor: serial number, Ethernet address, physical memory
Describe Drives
Provides info about on-line drives: drive numbers and size in pages of each one
Login
user provides new user name and password for use by ensuing commands
Reserve Alto Regions
allocates disk space for use by Alto emulation mode; this must be done before formatting and only pertains to Drive 0 (RD0).
Format Disk
prepares a disk for further use by the system. Writes a header on each sector of the disk for use by the disk hardware. Writes a random bit pattern in each sector, and verifies it is readable. May make a specifiable number of additional passes writing other random bit patterns and reading them back. At the end, a bad page table is created, and any bad pages that have been discovered are stored in it.
Run Diagnostic BCD
runs another program and attaches its commands to the list provided by Iago. The default program is ExtraIago.
Install Credentials
Aks you "Do you want to password-protect this disk?". A 'y answer makes the machine usable only by the currently logged-in user via normal booting. A 'n answer makes the machine available to anyone with Grapevine credentials. Beware: when password-protected a machine is still accessible using net booting.
Check Drive
scans a disk looking for hard and soft disk errors. At the end, any sectors with hard errors are added to the bad page table.
Commands Manipulating Physical and Logical Volumes
Create Physical Volume
builds data structures representing an entire disk (except Alto regions).
Create Logical Volume
builds data structures representing an independently named logical volume on a physical volume. A physical volume may contain many logical volumes. As each is created, you are prompted for its size.
Describe Logical Volumes, Describe Physical Volumes
lists all information about all logical or physical volumes
Erase Logical Volume
prepares a logical volume for use by File. Writes a label on each sector of the logical volume and builds the Volume Allocation Map (VAM). The label is a free page label, except for a few root files such as the VAM.
RecomputeVAM
scans a logical volume and ensures that the VAM and the sector labels agree about which sectors are allocated and which are free. The truth is in the labels, and the VAM is made consistent with them.
Cedar Installation Commands
Install Boot File
Copies a Cedar boot file, by default from a server, and makes it run as part of the boot sequence. This must be done whenever there is a new release of the boot file (usually whenever there is a new system release or "bounce").
Install Cedar Microcode, Install Germ, Install Initial Microcode
Each of these commands copies the appropriate file, by default from a server, and makes it part of the booting sequence. These commands usually need to be done only once per Format of the drive involved. They variously pertain to a disk or a logical volume.
Create VM Backing File
Creates a file to be used when pages must be swapped out of real memory. Can be on any logical volume. Size should be at least 16000 pages and no more than 32000 pages.
Set Physical Boot File, Set Physical Germ, Set Physical Microcode
Sets pointers on the disk to these files used in booting. The Install commands do the right thing, so I've never had cause to use these commands.
Create User World
A macro command that will do all the work to install Cedar on a naked system. Its default values may be out of date these days, but it will tell you what it will do before it does it. This can be quite useful if you have to do the sequence yourself but don't remember it all. Use Create User World to remind you of the steps to be done, hit DEL to quit out of it, and then do them manually.
See Also
ExtraIago.df: more tools for finding and fixing disk problems. Includes ExtraIagoDoc.tioga.
DiskErrorRecovery.tioga: instructions for using Iago and ExtraIago tools to repair some common disk problems.