Re: Use a CD-ROM as root?

[Jor-el <jorel@ibm.net>]

Michele,

	Well, I tried your program out on my Aptive S90. Its got some
pathological hardware which causes the cdrom not to be detected at boot
unless I specify the I/O addresses and IRQ's on the boot cmdline.

(a) Under a kernel which had been booted with the correct cmdline, the
program worked correctly.
(b) Under a kernel which had not been booted with the cmdline specifying
the I/O addresses and the IRQ's, the program failed. This proves - if it
proves anything at all - that the program will not work on all hardware.

	However, here is an interesting question. Here is my ide setup :

hda ---------> hard disk 1
hdb ---------> hard disk 2
hdc ---------> hard disk 3
hdd ---------> nothing
hde ---------> cdrom drive

	Here is the result of me putting a 'perror("fopen ")' after the
'fopen' in the function 'testdevice' of your program :

fopen : Success
Device open/test failed for /dev/hda     <---- Debugging msg printing *l
fopen : Success
Device open/test failed for /dev/hdb
fopen : Success
Device open/test failed for /dev/hdc
fopen : Device not configured
Device open/test failed for /dev/hdd
fopen : Operation not supported by device
Device open/test failed for /dev/hde
fopen : No such file or directory

(1)	Why does /dev/hdc get the message 'Device not configured'? This
disk contains the Debian install that I booted into to run this program.
(2)	The obvious question : why doesnt it work for /dev/hde?

Regards,
Jor-el

On Sun, 4 Apr 1999, Michele Dalla Silvestra wrote:

> On Sat, 3 Apr 1999, Jor-el wrote:
> 
> > 	I tried to clip out the gzipped program you sent in your mail, but
> > it didnt work. Could you either put in the source code, or send it as a
> > MIME atachment please?
> 
> Ok
> 
> ciao
> 
> 					Michele
> 
> 
> /*
>  isodetect.c 
> 
>  Looks in first block of an block-device and checks if there is an ISO9660-
>  filesystem on it. This is done by checking for a string "CD001".
>  
>  Also reads certain information out of the block.
> 
>  14.11.95 T.Niederreiter  (based on cdlabel.c by aeb)
> 
>  Copyright (C) 1999 - Michele Dalla Silvestra <dalla@debian.org>
>  Join detectcd, set_loop and mount function
> */
> 
> #include <stdio.h>
> #include <ctype.h>
> #include <unistd.h>
> #include <fcntl.h>
> #include <termio.h>
> #include <string.h>
> #include <sys/mount.h>
> #include <linux/loop.h>
> 
> 
> char *devlist[]={"/dev/hda","/dev/hdb","/dev/hdc","/dev/hdd",
> 		"/dev/hde","/dev/hdf","/dev/scd0","/dev/scd1",NULL};
> 
> 
> 
> int symlink(const char *oldpath, const char *newpath);
> int fileno( FILE *stream);
> 
> 
> int testdevice(char *dev)
> {
>   FILE *infile;
>   char buf[1024];
>   infile = fopen(dev,"rb");
>   if (infile == NULL)
>     return 1;
>   if (lseek(fileno(infile), 32768, SEEK_SET) < 0)
>     return 1;
>   if (read(fileno(infile), buf, sizeof(buf)) != sizeof(buf))
>     return 1;
>   if (strncmp(buf, "\001CD001\001", 8) != 0)
>     return 1;
>   else 
>     return 0;
> }
> 
> 
> int set_loop(const char *device, const char *file)
> {
>   struct loop_info loopinfo;
>   int fd, ffd;
>   if ((ffd=open(file,O_RDONLY))<0)
>     return 1;
>   if ((fd=open(device,O_RDONLY))<0)
>     return 1;
>   memset(&loopinfo, 0, sizeof(loopinfo));
>   strncpy(loopinfo.lo_name, file, LO_NAME_SIZE);
>   loopinfo.lo_name[LO_NAME_SIZE-1] = 0;
>   loopinfo.lo_encrypt_type = 0;
>   loopinfo.lo_offset = 0;
>   loopinfo.lo_encrypt_key_size = 0;
>   if (ioctl(fd, LOOP_SET_FD, ffd) < 0)
>   {
>     perror("ioctl: LOOP_SET_FD");
>     return 1;
>   }
>   if (ioctl(fd, LOOP_SET_STATUS, &loopinfo) < 0)
>   {
>     (void) ioctl(fd, LOOP_CLR_FD, 0);
>     perror("ioctl: LOOP_SET_STATUS");
>     return 1;
>   }
>   close(fd);
>   close(ffd);
>   return 0;
> }
> 
> 
> int main(int argc, char **argv)
> {
>   char **l=devlist;
>   while ((*l)!=NULL)
>     if (testdevice(*l)==0)
>       break;
>     else
>       l++;
>   if ((*l)!=NULL)
>   {
>     symlink(*l,"/dev/cdrom");
>     mount(*l,"/cdrom","iso9660",MS_MGC_VAL | MS_RDONLY,"");
>     set_loop("/dev/loop7","/cdrom/i386/debian-live.isofs");
>     mount("/dev/loop7","/looproot","iso9660",MS_MGC_VAL | MS_RDONLY,"");
>     mount("proc","/proc","proc",MS_MGC_VAL,"");
>   }
>   return 0;
> }
> 
>