IRIX 5.3 system: any access?

Scott Quinn compoobah at
Fri Apr 14 23:40:50 CDT 2006

Linux EFS works fine on SGI disks, as long as you have SGI disklabel support compiled in, but it is read-only.
XFS is read-write.

The mount device is, as was said, dks[scsi disk](x)d(y)s(z) with x the SCSI bus number, d the SCSI id number, and z the slice number.
The PROM is different, with SCSI drives represented as dksc(x,y,z). Other interfaces use diferent identifiers, like dkip.
common slices are 0 (root), 7 (option disk, non-bootable second drive, also used for CD-ROMs), 10 (the volume partition), 1 (swap),
8 (volume header) and 4 (usr, not present on modern default disklabels).

SASH (the Stand Alone SHell) is in the volume header and is instrumental in booting. The volume header is a small section of the disk that 
has a filesystem that can be understood by the PROM monitor. It contains the disklabel, symbolic monitor, IDE (interactive diagnostic environment)
and SASH. The firmware bootstrap machines load SASH from the volheader (which the ROM understands) and then SASH loads IRIX from the main filesystem (which it understands)
Really a cool system, you don't need anything to write a bootblock, and it is possible to load SASH from a CD-ROM and start the disk-resident copy of IRIX if your SASH is corrupted.
dvhtool is the IRIX utility provided for writing/reading the volheader. SASH, however, needs to be the correct version to understand the filesystem (a 5.3 EFS SASH can't boot a 6.2 XFS partition)
Since SASH understands the filesystem, you can use basic commands (cp, cat, ls, setenv), but no UNIX utilities like vi. If you could create an accessible replacement passwd, it could be copied
over on top of the original passwd file [dksc(0,1,0)/etc/passwd].  
You need to be very careful, especially with IRIX 5.3, to get a version that runs on your hardware. A big gotcha is with later machines that come with 2MB of cache (IRIX 5.3 base won't run on them)
6.2 is easier, there are only two versions, one for R10k Indigo2s and one for everyone else (the R10k I2 also supports all other I2s). It would be much easier if SGI had made later releases support all earlier machines, but they didn't. The 2MB cache issue can, in rumor, be sidestepped by installing base IRIX 5.3 using a 1MB cache CPU(PM1-PM5), applying all patches, and then plugging in the 2MB PM(6 or 7)

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