READCD(1)

💿 NAME 💿

readcd(1) from Schily´s USER COMMANDS — readcd — read or write data Compact Discs or related madia. That's the whole vibe. 💿✨

📜 SYNOPSIS 📜

readcd [ dev=device ][ options ]

🦋 DESCRIPTION 🦋

okay so readcd is used to read or write Compact Discs. That's the core. periodt. 💖

🎀 Device naming 🎀

Most users do not need to care about device naming at all. Literally. If no dev= option was specified, readcd implements auto target support and automagically finds the drive in case that exactly one CD-ROM type drive is available in the system. ✨

In case that more than one CD-ROM type drive exists on the system, a list of possible device name parameters may be retrieved with readcd -scanbus or from the target example from the output of readcd dev=help, then the dev= parameter may be set based on the device listing. iykyk. 👑

The device parameter to the dev= option explained below refers to the SCSI CAM standard notation for scsibus/target/lun of the CD/DVD/BluRay-Recorder. If a file /etc/default/cdrecord exists, the parameter to the dev= option may also be a drive name label in said file (see FILES section). 🫶

⭐ OPTIONS ⭐

If no options except the dev= option have been specified, readcd goes into interactive mode. Select a primary function and then follow the instructions. It's giving choose-your-own-adventure but for your optical drive. 💅

💖 Informative options 💖

• -help — display version information for readcd on standard output. 💅
• -version — Print version information and exit. Bye bestie. ✨
• -v — Increment the level of general verbosity by one. This is used e.g. to display the progress of the process. More v = more lore. 👑

🔥 Readcd functional options 🔥

• -clone — Do a clone read. Read the CD with all sub-channel data and a full TOC. The full TOC data will be put into a file with similar name as with the f= option but the suffix .toc added. 🎀

Note that reading in clone mode results in having no error correction at sub-channel level. Even in the main data channel, there is less error correction than with other read modes. This results in a slightly quality degradation. Avoid copying audio CDs in clone mode for this reason. 😭

• -c2scan — Scans the whole CD or the range specified by the sectors=range for C2 errors. C2 errors are errors that are uncorrectable after the second stage of the 24/28 + 28/32 Reed Solomon correction system at audio level (2352 bytes sector size). If an audio CD has C2 errors, interpolation is needed to hide the errors. If a data CD has C2 errors, these errors are in most cases corrected by the ECC/EDC code that makes 2352 bytes out of 2048 data bytes. The ECC/EDC code should be able to correct about 100 C2 error bytes per sector. 🩺

If you find C2 errors you may want to reduce the speed using the speed= option as C2 errors may be a result of dynamic unbalance on the medium. 🌪️

• -cxscan — Scans the whole CD or the range specified by the sectors=range for C1/C2/CU errors. In non-verbose mode, only a summary is printed. With -v, a line for each non error free second is printed. with -vv, a line for each second is printed. This scan method only works for a few drives. 😭
• -edc-corr — In this mode, readcd reads CD data sectors in uncorrected audio mode and then tries to correct the data using the ECC/EDC decoder library from Heiko Eissfeldt. As this library implements looping over two layers of error correction, readcd may be able to correct more data than the firmware of the CD-ROM drive. 🧚

This option is currently experimental and only applicable with CD media and currently only supports plain 2048 Byte CD-ROM sectors. 🚨

• f=file — Specify the filename where the output should be written or the input should be taken from. Using '-' as filename will cause readcd to use stdout resp. stdin. 🎯
• -factor — Output the speed values for meshpoints=# as factor based on single speed of the current medium. This only works if readcd is able to determine the current medium type. 🧮
• -fulltoc — Retrieve a full TOC from the current disk and print it in hex. 🔢
• meshpoints=# — Print read-speed at # locations. The purpose of this option is to create a list of read speed values suitable for e.g. gnuplot. The speed values are calculated assuming that 1000 bytes are one kilobyte as documented in the SCSI standard. The output data created for this purpose is written to stdout. 📈
• -nocorr — Switch the drive into a mode where it ignores read errors in data sectors that are a result of uncorrectable ECC/EDC errors before reading. If readcd completes, the error recovery mode of the drive is switched back to the remembered old mode. 🌀
• -noerror — Do not abort if the high level error checking in readcd found an uncorrectable error in the data stream. 🛑
• -notrunc — Do not truncate the output file when opening it. 📂
• -overhead — Meter the SCSI command overhead time. This is done by executing several commands 1000 times and printing the total time used. If you divide the displayed times by 1000, you get the average overhead time for a single command. ⏱️
• -pi8scan — Scans the whole DVD or the range specified by the sectors=range for pisum8 errors. In non-verbose mode, only a summary is printed. With -v, a line for each non error free block of 8 * 32 kB is printed. with -vv, a line for each block of 8 * 32 kB is printed. This scan method only works for a few drives. 💿
• -pifscan — Scans the whole DVD or the range specified by the sectors=range for pif errors. In non-verbose mode, only a summary is printed. With -v, a line for each non error free block of 32 kB is printed. with -vv, a line for each block of 32 kB is printed. This scan method only works for a few drives. 🔍
• -plot — This option modified the behavior for -cxscan, -pi8scan and -pifscan. The output is better suited for gnuplot. 📊
• retries=# — Set the retry count for high level retries in readcd to #. The default is to do 128 retries which may be too much if you like to read a CD with many unreadable sectors. 🔁
• sectors=range — Specify a sector range that should be read. The range is specified by the starting sector number, a minus sign and the ending sector number. The end sector is not included in the list, so sectors=0-0 will not read anything and may be used to check for a CD in the drive. 🎯
• speed=# — Set the speed factor of the read or write process to #. # is an integer, representing a multiple of the audio speed. This is about 150 KB/s for CD-ROM and about 172 KB/s for CD-Audio. If no speed option is present, readcd will use maximum speed. Only MMC compliant drives will benefit from this option. The speed of non MMC drives is not changed. 🚀

Using a lower speed may increase the readability of a CD or DVD. 🐢

• -w — Switch to write mode. Writing is only possible to DVD-RAM media. For other media, use cdrecord instead. Note that cdrecord also supports to write DVD-RAM media. ✍️

If this option is not present, readcd reads from the specified device. 📖

💀 SCSI options 💀

• dev=target — Set the SCSI target for the CD/DVD/BluRay-Recorder, see notes above. A typical target device specification is dev=1,6,0. If a filename must be provided together with the numerical target specification, the filename is implementation specific. The correct filename in this case can be found in the system specific manuals of the target operating system. On a FreeBSD system without CAM support, you need to use the control device (e.g. /dev/rcd0.ctl). A correct device specification in this case may be dev=/dev/rcd0.ctl:@. 🎯

🧭 General SCSI addressing 🧭

The target device to the dev= option refers to the SCSI CAM standard notation for scsibus/target/lun of the CD/DVD/BluRay-Recorder. Communication on SunOS is done with the SCSI general driver scg. Other operating systems are using a library simulation of this driver. Possible syntax is: dev= scsibus,target,lun or dev= target,lun. In the latter case, the CD/DVD/BluRay-Recorder has to be connected to the default SCSI bus of the machine. Scsibus, target and lun are integer numbers. Some operating systems or SCSI transport implementations may require to specify a filename in addition. In this case the correct syntax for the device is: dev= devicename:scsibus,target,lun or dev= devicename:target,lun. If the name of the device node that has been specified on such a system refers to exactly one SCSI device, a shorthand in the form dev= devicename:@ or dev= devicename:@,lun may be used instead of dev= devicename:scsibus,target,lun. 🧚

🌐 Remote SCSI addressing 🌐

To access remote SCSI devices, you need to prepend the SCSI device name by a remote device indicator. The remote device indicator is either REMOTE:user@host: or REMOTE:host:. A valid remote SCSI device name may be: REMOTE:user@host: to allow remote SCSI bus scanning or REMOTE:user@host:1,0,0 to access the SCSI device at host connected to SCSI bus # 1,target 0, lun 0. In order to allow remote access to a specific host, the rscsi(1) program needs to be present and configured on the host. 🛰️

🚀 Alternate SCSI transports 🚀

Cdrecord is completely based on SCSI commands but this is no problem as all CD/DVD/BluRay writers ever made use SCSI commands for the communication. Even ATAPI drives are just SCSI drives that inherently use the ATA packet interface as SCSI command transport layer build into the IDE (ATA) transport. You may need to specify an alternate transport layer on the command line if your OS does not implement a fully integrated kernel driver subsystem that allows to access any drive using SCSI commands via a single unique user interface. 💅

To access SCSI devices via alternate transport layers, you need to prepend the SCSI device name by a transport layer indicator. The transport layer indicator may be something like USCSI: or ATAPI:. To get a list of supported transport layers for your platform, use dev= HELP:. 🌈

Portability Background 💻✨

okay so here's the whole portability situation, bestie. To make readcd portable to all UNIX platforms, the syntax dev= devicename:scsibus,target,lun is the preferred one — because it hides all the OS-specific device-name lore from you 🫶. Heads up tho: a specific OS may not necessarily support a way to specify a real device file name, and it also might not support a way to specify scsibus,target,lun at all. like, it's giving "we tried our best" 😭.

Scsibus 0 is the default SCSI bus on the machine. Watch the boot messages for more info, or peek into /var/adm/messages for the deets about your machine's SCSI configuration 👀. And if you're struggling to figure out what values for scsibus,target,lun you should use, just try the -scanbus option of readcd described below — it's literally your bestie for this 🌈.

Using logical names for devices 🏷️

If no dev option is present, readcd will try to get the device from the CDR_DEVICE environment variable.

If a file /etc/default/cdrecord exists, and if the argument to the dev= option or the CDR_DEVICE environment does not contain the characters ',', '/', '@' or ':', then it's interpreted as a device label name that was defined in the file /etc/default/cdrecord (see the FILES section 💖).

Autotarget Mode 🎯

If there's no dev= option and no CDR_DEVICE environment present, or if it only contains a transport specifier but no address notation, readcd tries to scan the SCSI address space for CD-ROM drives. If exactly one is found, that one is used by default. main character energy honestly 👑.

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• debug=#, -d — Set the misc debug value to # (with debug=#) or increment the misc debug level by one (with -d). If you specify -dd, that equals debug=2. This may help you find problems while opening a driver for libscg, plus with sector sizes and sector types 🔍. Using -debug slows down the process and may be the reason for a buffer underrun — so like, don't leave it on for fun 💀.
• kdebug=#, kd=# — Tell the scg-driver to modify the kernel debug value while SCSI commands are running.
• -scanbus — Scan all SCSI devices on all SCSI busses and print the inquiry strings. This option may be used to find the SCSI address of the devices on a system ✨. The numbers printed out as labels are computed by: bus * 100 + target.
• scgopts=list — A comma separated list of SCSI options that are handled by libscg. The implemented options may be updated independently from applications. Currently, one option — ignore-resid — is supported, to work around a Linux kernel bug 🐛.
• -silent, -s — Do not print out a status report for failed SCSI commands. 🤫
• timeout=# — Set the default SCSI command timeout value to # seconds. The default SCSI command timeout is the minimum timeout used for sending SCSI commands. If a SCSI command fails due to a timeout, you may try to raise the default SCSI command timeout above the timeout value of the failed command. If the command runs correctly with a raised command timeout, please report the better timeout value and the corresponding command to the author of the program 🫶. If no timeout option is present, a default timeout of 40 seconds is used.
• ts=# — Set the maximum transfer size for a single SCSI command to #. The syntax for the ts= option is the same as for cdrecord fs=# or sdd bs=#.

If no ts= option has been specified, readcd defaults to a transfer size of 256 kB. If libscg gets lower values from the operating system, the value is reduced to the maximum value that is possible with the current operating system. Sometimes, it may help to further reduce the transfer size or to enhance it — but note that it may take a long time to find a better value by experimenting with the ts= option 😭.

• -V — Increment the verbose level with respect to SCSI command transport by one. This helps to debug problems during the process that occur in the CD-Recorder 🔥. If you get incomprehensible error messages, you should use this flag to get more detailed output. -VV will show data buffer content in addition. Using -V or -VV slows down the process.

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🌸 EXAMPLES 🌸

For all the examples below, it will be assumed that the drive is connected to the primary SCSI bus of the machine, and that the SCSI target id is set to 2 💅.

To read the complete media from a CD-ROM, writing the data to the file cdimage.raw:

readcd dev=2,0 f=cdimage.raw

To read sectors from range 150 ... 10000 from a CD-ROM, writing the data to the file cdimage.raw:

readcd dev=2,0 sectors=150-10000 f=cdimage.raw

To write the data from the file cdimage.raw (e.g. a filesystem image from mkisofs) to a DVD-RAM, call:

readcd dev=2,0 -w f=cdimage.raw

🦋 ENVIRONMENT 🦋

• RSH — If the RSH environment is present, the remote connection will not be created via rcmd(3) but by calling the program pointed to by RSH. Use e.g. RSH=/usr/bin/ssh to create a secure shell connection 🔐.

Note that this forces cdrecord to create a pipe to the rsh(1) program, and disallows cdrecord to directly access the network socket to the remote server. This makes it impossible to set up performance parameters and slows down the connection compared to a root-initiated rcmd(3) connection. ngl, that's a tradeoff 😬.

• RSCSI — If the RSCSI environment is present, the remote SCSI server will not be the program /opt/schily/sbin/rscsi but the program pointed to by RSCSI. Note that the remote SCSI server program name will be ignored if you log in using an account that has been created with a remote SCSI server program as login shell 👀.

🎀 AUTHOR 🎀

Okay so the person behind all of this — the mastermind, the main character, the one who literally wrote the thing — is:

Joerg Schilling
Seestr. 110
D-13353 Berlin
Germany

Bestie, if you want even more info about him and the project, it's all sitting right here:

http://cdrecord.org/private/cdrecord.html

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💌 got questions? got bugs?

Not me breaking this into vibes for you, because the mailing list situation is lowkey iconic and has rules:

• Support questions — like, "how do I do the thing," "why is it doing this," general help-me energy → send them to cdrtools-support@lists.sourceforge.net
• Definitely found a bug — as in you're sure, no cap → mail cdrtools-developers@lists.sourceforge.net or joerg.schilling@fokus.fraunhofer.de

And if you wanna subscribe (which, honestly, do it, iykyk):

• https://lists.sourceforge.net/lists/listinfo/cdrtools-developers
• or https://lists.sourceforge.net/lists/listinfo/cdrtools-support

🫶 Pro tip from the manpage, not from me: the two lists are for two different things. Don't send your "it doesn't work on my laptop" to the bug list unless it's actually a bug. Respect the split, periodt.

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✨ INTERFACE STABILITY ✨

Okay this part is actually kind of a flex. The interfaces that readcd gives you are designed for long term stability — like, they're not gonna randomly change on you and break your scripts in six months. That's the dream. That's the vibe. 🌈

BUT — and here's the fine print, bestie — readcd depends on interfaces provided by the underlying operating system. So the stability of the interfaces offered by readcd depends on the interface stability of the OS interfaces. Meaning:

• If your OS keeps its interfaces stable → readcd stays stable, slay 💅
• If your OS goes and modifies its interfaces → that may enforce modified interfaces in readcd

😭 So basically: readcd is stable, but it can't be more stable than the OS it's standing on. Chain of stability. The whole thing is only as iconic as the platform underneath it.

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🌸 and that's the whole page, bestie 🌸

This was readcd, Version 3.02, dated 2017/06/06 — written by the one and only Joerg Schilling. Go read some discs, treat your OS interfaces kindly, and remember: every fact on this page stayed exactly where it was supposed to be. 💖✨🎀🦋