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Full Discussion: How raw disks are read?
Top Forums UNIX for Advanced & Expert Users How raw disks are read? Post 302802765 by methyl on Saturday 4th of May 2013 06:13:54 PM
Old 05-04-2013
Point: With modern hardware a "raw disc" can be multiple physical discs which the Operating System sees as one physical disc.

Some research ideas:

Consider the case of a virgin disc. There are no filesystems unless your software creates a filesystem. You can write or read whatever you like within the physical dimensions of the disc.

The very basic filesystems follow the pattern of the original IBM tape format VOL1 HDR1.

For research purposes it is worth a look at CAFS (Content Addressable File Store). That's the way to use a raw disc! It's so much better than "Binary Tree", "Hash Random" or "Index Sequential" file systems when dealing with disorganised data.
 

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APT-CDROM(8)								APT							      APT-CDROM(8)

NAME
apt-cdrom - APT CD-ROM management utility SYNOPSIS
apt-cdrom [-rmfan] [-d=cdrom_mount_point] [-o=config_string] [-c=config_file] {add | ident | {-v | --version} | {-h | --help}} DESCRIPTION
apt-cdrom is used to add a new CD-ROM to APT's list of available sources. apt-cdrom takes care of determining the structure of the disc as well as correcting for several possible mis-burns and verifying the index files. It is necessary to use apt-cdrom to add CDs to the APT system; it cannot be done by hand. Furthermore each disc in a multi-CD set must be inserted and scanned separately to account for possible mis-burns. Unless the -h, or --help option is given, one of the commands below must be present. add add is used to add a new disc to the source list. It will unmount the CD-ROM device, prompt for a disc to be inserted and then proceed to scan it and copy the index files. If the disc does not have a proper .disk directory you will be prompted for a descriptive title. APT uses a CD-ROM ID to track which disc is currently in the drive and maintains a database of these IDs in /var/lib/apt/cdroms.list ident A debugging tool to report the identity of the current disc as well as the stored file name OPTIONS
All command line options may be set using the configuration file, the descriptions indicate the configuration option to set. For boolean options you can override the config file by using something like -f-,--no-f, -f=no or several other variations. --no-auto-detect, --cdrom Do not try to auto-detect the CD-ROM path. Usually combined with the --cdrom option. Configuration Item: Acquire::cdrom::AutoDetect. -d, --cdrom Mount point; specify the location to mount the CD-ROM. This mount point must be listed in /etc/fstab and properly configured. Configuration Item: Acquire::cdrom::mount. -r, --rename Rename a disc; change the label of a disc or override the disc's given label. This option will cause apt-cdrom to prompt for a new label. Configuration Item: APT::CDROM::Rename. -m, --no-mount No mounting; prevent apt-cdrom from mounting and unmounting the mount point. Configuration Item: APT::CDROM::NoMount. -f, --fast Fast Copy; Assume the package files are valid and do not check every package. This option should be used only if apt-cdrom has been run on this disc before and did not detect any errors. Configuration Item: APT::CDROM::Fast. -a, --thorough Thorough Package Scan; This option may be needed with some old Debian 1.1/1.2 discs that have Package files in strange places. It takes much longer to scan the CD but will pick them all up. -n, --just-print, --recon, --no-act No Changes; Do not change the sources.list(5) file and do not write index files. Everything is still checked however. Configuration Item: APT::CDROM::NoAct. -h, --help Show a short usage summary. -v, --version Show the program version. -c, --config-file Configuration File; Specify a configuration file to use. The program will read the default configuration file and then this configuration file. If configuration settings need to be set before the default configuration files are parsed specify a file with the APT_CONFIG environment variable. See apt.conf(5) for syntax information. -o, --option Set a Configuration Option; This will set an arbitrary configuration option. The syntax is -o Foo::Bar=bar. -o and --option can be used multiple times to set different options. SEE ALSO
apt.conf(5), apt-get(8), sources.list(5) DIAGNOSTICS
apt-cdrom returns zero on normal operation, decimal 100 on error. BUGS
APT bug page[1]. If you wish to report a bug in APT, please see /usr/share/doc/debian/bug-reporting.txt or the reportbug(1) command. AUTHORS
Jason Gunthorpe APT team NOTES
1. APT bug page http://bugs.debian.org/src:apt APT 1.6.3ubuntu0.1 30 November 2013 APT-CDROM(8)
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