| 1 | <?xml version="1.0" encoding="UTF-8"?> |
| 2 | <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" |
| 3 | "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [ |
| 4 | <!ENTITY % aptent SYSTEM "apt.ent"> %aptent; |
| 5 | <!ENTITY % aptverbatiment SYSTEM "apt-verbatim.ent"> %aptverbatiment; |
| 6 | <!ENTITY % aptvendor SYSTEM "apt-vendor.ent"> %aptvendor; |
| 7 | ]> |
| 8 | |
| 9 | <book lang="en"> |
| 10 | |
| 11 | <title>APT Method Interface</title> |
| 12 | |
| 13 | <bookinfo> |
| 14 | |
| 15 | <authorgroup> |
| 16 | <author> |
| 17 | <personname>Jason Gunthorpe</personname><email>jgg@debian.org</email> |
| 18 | </author> |
| 19 | </authorgroup> |
| 20 | |
| 21 | <releaseinfo>Version &apt-product-version;</releaseinfo> |
| 22 | |
| 23 | <abstract> |
| 24 | <para> |
| 25 | This document describes the interface that APT uses to the archive access |
| 26 | methods. |
| 27 | </para> |
| 28 | </abstract> |
| 29 | |
| 30 | <copyright><year>1998</year><holder>Jason Gunthorpe</holder></copyright> |
| 31 | |
| 32 | <legalnotice> |
| 33 | <title>License Notice</title> |
| 34 | <para> |
| 35 | "APT" and this document are free software; you can redistribute them and/or |
| 36 | modify them under the terms of the GNU General Public License as published by |
| 37 | the Free Software Foundation; either version 2 of the License, or (at your |
| 38 | option) any later version. |
| 39 | </para> |
| 40 | <para> |
| 41 | For more details, on Debian systems, see the file |
| 42 | /usr/share/common-licenses/GPL for the full license. |
| 43 | </para> |
| 44 | </legalnotice> |
| 45 | |
| 46 | </bookinfo> |
| 47 | |
| 48 | <chapter id="ch1"><title>Introduction</title> |
| 49 | |
| 50 | <section id="s1.1"><title>General</title> |
| 51 | <para> |
| 52 | The APT method interface allows APT to acquire archive files (.deb), index |
| 53 | files (Packages, Release, Mirrors) and source files (.tar.gz, .diff). It is a |
| 54 | general, extensible system designed to satisfy all of these requirements: |
| 55 | </para> |
| 56 | <orderedlist numeration="arabic"> |
| 57 | <listitem> |
| 58 | <para> |
| 59 | Remote methods that download files from a distant site |
| 60 | </para> |
| 61 | </listitem> |
| 62 | <listitem> |
| 63 | <para> |
| 64 | Resume of aborted downloads |
| 65 | </para> |
| 66 | </listitem> |
| 67 | <listitem> |
| 68 | <para> |
| 69 | Progress reporting |
| 70 | </para> |
| 71 | </listitem> |
| 72 | <listitem> |
| 73 | <para> |
| 74 | If-Modified-Since (IMS) checking for index files |
| 75 | </para> |
| 76 | </listitem> |
| 77 | <listitem> |
| 78 | <para> |
| 79 | In-Line MD5 generation |
| 80 | </para> |
| 81 | </listitem> |
| 82 | <listitem> |
| 83 | <para> |
| 84 | No-copy in-filesystem methods |
| 85 | </para> |
| 86 | </listitem> |
| 87 | <listitem> |
| 88 | <para> |
| 89 | Multi-media methods (like CD's) |
| 90 | </para> |
| 91 | </listitem> |
| 92 | <listitem> |
| 93 | <para> |
| 94 | Dynamic source selection for failure recovery |
| 95 | </para> |
| 96 | </listitem> |
| 97 | <listitem> |
| 98 | <para> |
| 99 | User interaction for user/password requests and media swaps |
| 100 | </para> |
| 101 | </listitem> |
| 102 | <listitem> |
| 103 | <para> |
| 104 | Global configuration |
| 105 | </para> |
| 106 | </listitem> |
| 107 | </orderedlist> |
| 108 | <para> |
| 109 | Initial releases of APT (0.1.x) used a completely different method interface |
| 110 | that only supported the first 6 items. This new interface deals with the |
| 111 | remainder. |
| 112 | </para> |
| 113 | </section> |
| 114 | |
| 115 | <section id="s1.2"><title>Terms</title> |
| 116 | <para> |
| 117 | Several terms are used through out the document, they have specific meanings |
| 118 | which may not be immediately evident. To clarify they are summarized here. |
| 119 | </para> |
| 120 | <variablelist> |
| 121 | <varlistentry> |
| 122 | <term>source</term> |
| 123 | <listitem> |
| 124 | <para> |
| 125 | Refers to an item in source list. More specifically it is the broken down |
| 126 | item, that is each source maps to exactly one index file. Archive sources map |
| 127 | to Package files and Source Code sources map to Source files. |
| 128 | </para> |
| 129 | </listitem> |
| 130 | </varlistentry> |
| 131 | <varlistentry> |
| 132 | <term>archive file</term> |
| 133 | <listitem> |
| 134 | <para> |
| 135 | Refers to a binary package archive (.deb, .rpm, etc). |
| 136 | </para> |
| 137 | </listitem> |
| 138 | </varlistentry> |
| 139 | <varlistentry> |
| 140 | <term>source file</term> |
| 141 | <listitem> |
| 142 | <para> |
| 143 | Refers to one of the files making up the source code of a package. In debian |
| 144 | it is one of .diff.gz, .dsc. or .tar.gz. |
| 145 | </para> |
| 146 | </listitem> |
| 147 | </varlistentry> |
| 148 | <varlistentry> |
| 149 | <term>URI</term> |
| 150 | <listitem> |
| 151 | <para> |
| 152 | Universal Resource Identifier (URI) is a super-set of the familiar URL |
| 153 | syntax used by web browsers. It consists of an access specification |
| 154 | followed by a specific location in that access space. The form is |
| 155 | <access>:<location>. Network addresses are given with the form |
| 156 | <access>://[<user>[:<pas>]@]hostname[:port]/<location>. |
| 157 | Some examples: |
| 158 | </para> |
| 159 | <screen> |
| 160 | file:/var/mirrors/debian/ |
| 161 | ftp://ftp.debian.org/debian |
| 162 | ftp://jgg:MooCow@localhost:21/debian |
| 163 | nfs://bigred/var/mirrors/debian |
| 164 | rsync://debian.midco.net/debian |
| 165 | cdrom:Debian 2.0r1 Disk 1/ |
| 166 | </screen> |
| 167 | </listitem> |
| 168 | </varlistentry> |
| 169 | <varlistentry> |
| 170 | <term>method</term> |
| 171 | <listitem> |
| 172 | <para> |
| 173 | There is a one to one mapping of URI access specifiers to methods. A method is |
| 174 | a program that knows how to handle a URI access type and operates according to |
| 175 | the specifications in this file. |
| 176 | </para> |
| 177 | </listitem> |
| 178 | </varlistentry> |
| 179 | <varlistentry> |
| 180 | <term>method instance</term> |
| 181 | <listitem> |
| 182 | <para> |
| 183 | A specific running method. There can be more than one instance of each method |
| 184 | as APT is capable of concurrent method handling. |
| 185 | </para> |
| 186 | </listitem> |
| 187 | </varlistentry> |
| 188 | <varlistentry> |
| 189 | <term>message</term> |
| 190 | <listitem> |
| 191 | <para> |
| 192 | A series of lines terminated by a blank line sent down one of the communication |
| 193 | lines. The first line should have the form xxx TAG where xxx are digits |
| 194 | forming the status code and TAG is an informational string |
| 195 | </para> |
| 196 | </listitem> |
| 197 | </varlistentry> |
| 198 | <varlistentry> |
| 199 | <term>acquire</term> |
| 200 | <listitem> |
| 201 | <para> |
| 202 | The act of bring a URI into the local pathname space. This may simply be |
| 203 | verifying the existence of the URI or actually downloading it from a remote |
| 204 | site. |
| 205 | </para> |
| 206 | </listitem> |
| 207 | </varlistentry> |
| 208 | </variablelist> |
| 209 | </section> |
| 210 | |
| 211 | </chapter> |
| 212 | |
| 213 | <chapter id="ch2"><title>Specification</title> |
| 214 | |
| 215 | <section id="s2.1"><title>Overview</title> |
| 216 | <para> |
| 217 | All methods operate as a sub process of a main controlling parent. 3 FD's are |
| 218 | opened for use by the method allowing two way communication and emergency error |
| 219 | reporting. The FD's correspond to the well known unix FD's, stdin, stdout and |
| 220 | stderr. |
| 221 | </para> |
| 222 | <para> |
| 223 | Through operation of the method communication is done via http style plain |
| 224 | text. Specifically RFC-822 (like the Package file) fields are used to describe |
| 225 | items and a numeric-like header is used to indicate what is happening. Each of |
| 226 | these distinct communication messages should be sent quickly and without pause. |
| 227 | </para> |
| 228 | <para> |
| 229 | In some instances APT may pre-invoke a method to allow things like file URI's |
| 230 | to determine how many files are available locally. |
| 231 | </para> |
| 232 | </section> |
| 233 | |
| 234 | <section id="s2.2"><title>Message Overview</title> |
| 235 | <para> |
| 236 | The first line of each message is called the message header. The first 3 |
| 237 | digits (called the Status Code) have the usual meaning found in the http |
| 238 | protocol. 1xx is informational, 2xx is successful and 4xx is failure. The 6xx |
| 239 | series is used to specify things sent to the method. After the status code is |
| 240 | an informational string provided for visual debugging. |
| 241 | </para> |
| 242 | <itemizedlist> |
| 243 | <listitem> |
| 244 | <para> |
| 245 | 100 Capabilities - Method capabilities |
| 246 | </para> |
| 247 | </listitem> |
| 248 | <listitem> |
| 249 | <para> |
| 250 | 101 Log - General Logging |
| 251 | </para> |
| 252 | </listitem> |
| 253 | <listitem> |
| 254 | <para> |
| 255 | 102 Status - Inter-URI status reporting (login progress) |
| 256 | </para> |
| 257 | </listitem> |
| 258 | <listitem> |
| 259 | <para> |
| 260 | 200 URI Start - URI is starting acquire |
| 261 | </para> |
| 262 | </listitem> |
| 263 | <listitem> |
| 264 | <para> |
| 265 | 201 URI Done - URI is finished acquire |
| 266 | </para> |
| 267 | </listitem> |
| 268 | <listitem> |
| 269 | <para> |
| 270 | 400 URI Failure - URI has failed to acquire |
| 271 | </para> |
| 272 | </listitem> |
| 273 | <listitem> |
| 274 | <para> |
| 275 | 401 General Failure - Method did not like something sent to it |
| 276 | </para> |
| 277 | </listitem> |
| 278 | <listitem> |
| 279 | <para> |
| 280 | 402 Authorization Required - Method requires authorization to access the URI. |
| 281 | Authorization is User/Pass |
| 282 | </para> |
| 283 | </listitem> |
| 284 | <listitem> |
| 285 | <para> |
| 286 | 403 Media Failure - Method requires a media change |
| 287 | </para> |
| 288 | </listitem> |
| 289 | <listitem> |
| 290 | <para> |
| 291 | 600 URI Acquire - Request a URI be acquired |
| 292 | </para> |
| 293 | </listitem> |
| 294 | <listitem> |
| 295 | <para> |
| 296 | 601 Configuration - Sends the configuration space |
| 297 | </para> |
| 298 | </listitem> |
| 299 | <listitem> |
| 300 | <para> |
| 301 | 602 Authorization Credentials - Response to the 402 message |
| 302 | </para> |
| 303 | </listitem> |
| 304 | <listitem> |
| 305 | <para> |
| 306 | 603 Media Changed - Response to the 403 message |
| 307 | </para> |
| 308 | </listitem> |
| 309 | </itemizedlist> |
| 310 | <para> |
| 311 | Only the 6xx series of status codes is sent TO the method. Furthermore the |
| 312 | method may not emit status codes in the 6xx range. The Codes 402 and 403 |
| 313 | require that the method continue reading all other 6xx codes until the proper |
| 314 | 602/603 code is received. This means the method must be capable of handling an |
| 315 | unlimited number of 600 messages. |
| 316 | </para> |
| 317 | <para> |
| 318 | The flow of messages starts with the method sending out a <emphasis>100 |
| 319 | Capabilities</emphasis> and APT sending out a <emphasis>601 |
| 320 | Configuration</emphasis>. After that APT begins sending <emphasis>600 URI |
| 321 | Acquire</emphasis> and the method sends out <emphasis>200 URI Start</emphasis>, |
| 322 | <emphasis>201 URI Done</emphasis> or <emphasis>400 URI Failure</emphasis>. No |
| 323 | synchronization is performed, it is expected that APT will send <emphasis>600 |
| 324 | URI Acquire</emphasis> messages at -any- time and that the method should queue |
| 325 | the messages. This allows methods like http to pipeline requests to the remote |
| 326 | server. It should be noted however that APT will buffer messages so it is not |
| 327 | necessary for the method to be constantly ready to receive them. |
| 328 | </para> |
| 329 | </section> |
| 330 | |
| 331 | <section id="s2.3"><title>Header Fields</title> |
| 332 | <para> |
| 333 | The following is a short index of the header fields that are supported |
| 334 | </para> |
| 335 | <variablelist> |
| 336 | <varlistentry> |
| 337 | <term>URI</term> |
| 338 | <listitem> |
| 339 | <para> |
| 340 | URI being described by the message |
| 341 | </para> |
| 342 | </listitem> |
| 343 | </varlistentry> |
| 344 | <varlistentry> |
| 345 | <term>Filename</term> |
| 346 | <listitem> |
| 347 | <para> |
| 348 | Location in the filesystem |
| 349 | </para> |
| 350 | </listitem> |
| 351 | </varlistentry> |
| 352 | <varlistentry> |
| 353 | <term>Last-Modified</term> |
| 354 | <listitem> |
| 355 | <para> |
| 356 | A time stamp in RFC1123 notation for use by IMS checks |
| 357 | </para> |
| 358 | </listitem> |
| 359 | </varlistentry> |
| 360 | <varlistentry> |
| 361 | <term>IMS-Hit</term> |
| 362 | <listitem> |
| 363 | <para> |
| 364 | The already existing item is valid |
| 365 | </para> |
| 366 | </listitem> |
| 367 | </varlistentry> |
| 368 | <varlistentry> |
| 369 | <term>Size</term> |
| 370 | <listitem> |
| 371 | <para> |
| 372 | Size of the file in bytes |
| 373 | </para> |
| 374 | </listitem> |
| 375 | </varlistentry> |
| 376 | <varlistentry> |
| 377 | <term>Resume-Point</term> |
| 378 | <listitem> |
| 379 | <para> |
| 380 | Location that transfer was started |
| 381 | </para> |
| 382 | </listitem> |
| 383 | </varlistentry> |
| 384 | <varlistentry> |
| 385 | <term>MD5-Hash</term> |
| 386 | <listitem> |
| 387 | <para> |
| 388 | Computed MD5 hash for the file |
| 389 | </para> |
| 390 | </listitem> |
| 391 | </varlistentry> |
| 392 | <varlistentry> |
| 393 | <term>Message</term> |
| 394 | <listitem> |
| 395 | <para> |
| 396 | String indicating some displayable message |
| 397 | </para> |
| 398 | </listitem> |
| 399 | </varlistentry> |
| 400 | <varlistentry> |
| 401 | <term>Media</term> |
| 402 | <listitem> |
| 403 | <para> |
| 404 | String indicating the media name required |
| 405 | </para> |
| 406 | </listitem> |
| 407 | </varlistentry> |
| 408 | <varlistentry> |
| 409 | <term>Site</term> |
| 410 | <listitem> |
| 411 | <para> |
| 412 | String indicating the site authorization is required for |
| 413 | </para> |
| 414 | </listitem> |
| 415 | </varlistentry> |
| 416 | <varlistentry> |
| 417 | <term>User</term> |
| 418 | <listitem> |
| 419 | <para> |
| 420 | Username for authorization |
| 421 | </para> |
| 422 | </listitem> |
| 423 | </varlistentry> |
| 424 | <varlistentry> |
| 425 | <term>Password</term> |
| 426 | <listitem> |
| 427 | <para> |
| 428 | Password for authorization |
| 429 | </para> |
| 430 | </listitem> |
| 431 | </varlistentry> |
| 432 | <varlistentry> |
| 433 | <term>Fail</term> |
| 434 | <listitem> |
| 435 | <para> |
| 436 | Operation failed |
| 437 | </para> |
| 438 | </listitem> |
| 439 | </varlistentry> |
| 440 | <varlistentry> |
| 441 | <term>Drive</term> |
| 442 | <listitem> |
| 443 | <para> |
| 444 | Drive the media should be placed in |
| 445 | </para> |
| 446 | </listitem> |
| 447 | </varlistentry> |
| 448 | <varlistentry> |
| 449 | <term>Config-Item</term> |
| 450 | <listitem> |
| 451 | <para> |
| 452 | A string of the form |
| 453 | <replaceable>item</replaceable>=<replaceable>value</replaceable> derived from |
| 454 | the APT configuration space. These may include method specific values and |
| 455 | general values not related to the method. It is up to the method to filter out |
| 456 | the ones it wants. |
| 457 | </para> |
| 458 | </listitem> |
| 459 | </varlistentry> |
| 460 | <varlistentry> |
| 461 | <term>Single-Instance</term> |
| 462 | <listitem> |
| 463 | <para> |
| 464 | Requires that only one instance of the method be run This is a yes/no value. |
| 465 | </para> |
| 466 | </listitem> |
| 467 | </varlistentry> |
| 468 | <varlistentry> |
| 469 | <term>Pipeline</term> |
| 470 | <listitem> |
| 471 | <para> |
| 472 | The method is capable of pipelining. |
| 473 | </para> |
| 474 | </listitem> |
| 475 | </varlistentry> |
| 476 | <varlistentry> |
| 477 | <term>Local</term> |
| 478 | <listitem> |
| 479 | <para> |
| 480 | The method only returns Filename: fields. |
| 481 | </para> |
| 482 | </listitem> |
| 483 | </varlistentry> |
| 484 | <varlistentry> |
| 485 | <term>Send-Config</term> |
| 486 | <listitem> |
| 487 | <para> |
| 488 | Send configuration to the method. |
| 489 | </para> |
| 490 | </listitem> |
| 491 | </varlistentry> |
| 492 | <varlistentry> |
| 493 | <term>Needs-Cleanup</term> |
| 494 | <listitem> |
| 495 | <para> |
| 496 | The process is kept around while the files it returned are being used. This is |
| 497 | primarily intended for CD-ROM and File URIs that need to unmount filesystems. |
| 498 | </para> |
| 499 | </listitem> |
| 500 | </varlistentry> |
| 501 | <varlistentry> |
| 502 | <term>Version</term> |
| 503 | <listitem> |
| 504 | <para> |
| 505 | Version string for the method |
| 506 | </para> |
| 507 | </listitem> |
| 508 | </varlistentry> |
| 509 | </variablelist> |
| 510 | <para> |
| 511 | This is a list of which headers each status code can use |
| 512 | </para> |
| 513 | <variablelist> |
| 514 | <varlistentry> |
| 515 | <term>100 Capabilities</term> |
| 516 | <listitem> |
| 517 | <para> |
| 518 | Displays the capabilities of the method. Methods should set the pipeline bit |
| 519 | if their underlying protocol supports pipelining. The only known method that |
| 520 | does support pipelining is http. Fields: Version, Single-Instance, Pre-Scan, |
| 521 | Pipeline, Send-Config, Needs-Cleanup |
| 522 | </para> |
| 523 | </listitem> |
| 524 | </varlistentry> |
| 525 | <varlistentry> |
| 526 | <term>101 Log</term> |
| 527 | <listitem> |
| 528 | <para> |
| 529 | A log message may be printed to the screen if debugging is enabled. This is |
| 530 | only for debugging the method. Fields: Message |
| 531 | </para> |
| 532 | </listitem> |
| 533 | </varlistentry> |
| 534 | <varlistentry> |
| 535 | <term>102 Status</term> |
| 536 | <listitem> |
| 537 | <para> |
| 538 | Message gives a progress indication for the method. It can be used to show |
| 539 | pre-transfer status for Internet type methods. Fields: Message |
| 540 | </para> |
| 541 | </listitem> |
| 542 | </varlistentry> |
| 543 | <varlistentry> |
| 544 | <term>200 URI Start</term> |
| 545 | <listitem> |
| 546 | <para> |
| 547 | Indicates the URI is starting to be transferred. The URI is specified along |
| 548 | with stats about the file itself. Fields: URI, Size, Last-Modified, |
| 549 | Resume-Point |
| 550 | </para> |
| 551 | </listitem> |
| 552 | </varlistentry> |
| 553 | <varlistentry> |
| 554 | <term>201 URI Done</term> |
| 555 | <listitem> |
| 556 | <para> |
| 557 | Indicates that a URI has completed being transferred. It is possible to |
| 558 | specify a <emphasis>201 URI Done</emphasis> without a <emphasis>URI |
| 559 | Start</emphasis> which would mean no data was transferred but the file is now |
| 560 | available. A Filename field is specified when the URI is directly available in |
| 561 | the local pathname space. APT will either directly use that file or copy it |
| 562 | into another location. It is possible to return Alt-* fields to indicate that |
| 563 | another possibility for the URI has been found in the local pathname space. |
| 564 | This is done if a decompressed version of a .gz file is found. Fields: URI, |
| 565 | Size, Last-Modified, Filename, MD5-Hash |
| 566 | </para> |
| 567 | </listitem> |
| 568 | </varlistentry> |
| 569 | <varlistentry> |
| 570 | <term>400 URI Failure</term> |
| 571 | <listitem> |
| 572 | <para> |
| 573 | Indicates a fatal URI failure. The URI is not retrievable from this source. As |
| 574 | with <emphasis>201 URI Done</emphasis> <emphasis>200 URI Start</emphasis> is |
| 575 | not required to precede this message Fields: URI, Message |
| 576 | </para> |
| 577 | </listitem> |
| 578 | </varlistentry> |
| 579 | <varlistentry> |
| 580 | <term>401 General Failure</term> |
| 581 | <listitem> |
| 582 | <para> |
| 583 | Indicates that some unspecific failure has occurred and the method is unable |
| 584 | to continue. The method should terminate after sending this message. It |
| 585 | is intended to check for invalid configuration options or other severe |
| 586 | conditions. Fields: Message |
| 587 | </para> |
| 588 | </listitem> |
| 589 | </varlistentry> |
| 590 | <varlistentry> |
| 591 | <term>402 Authorization Required</term> |
| 592 | <listitem> |
| 593 | <para> |
| 594 | The method requires a Username and Password pair to continue. After sending |
| 595 | this message the method will expect APT to send a <emphasis>602 Authorization |
| 596 | Credentials</emphasis> message with the required information. It is possible |
| 597 | for a method to send this multiple times. Fields: Site |
| 598 | </para> |
| 599 | </listitem> |
| 600 | </varlistentry> |
| 601 | <varlistentry> |
| 602 | <term>403 Media Failure</term> |
| 603 | <listitem> |
| 604 | <para> |
| 605 | A method that deals with multiple media requires that a new media be |
| 606 | inserted. The Media field contains the name of the media to be |
| 607 | inserted. Fields: Media, Drive |
| 608 | </para> |
| 609 | </listitem> |
| 610 | </varlistentry> |
| 611 | <varlistentry> |
| 612 | <term>600 URI Acquire</term> |
| 613 | <listitem> |
| 614 | <para> |
| 615 | APT is requesting that a new URI be added to the acquire list. Last-Modified |
| 616 | has the time stamp of the currently cache file if applicable. Filename is the |
| 617 | name of the file that the acquired URI should be written to. Fields: URI, |
| 618 | Filename Last-Modified |
| 619 | </para> |
| 620 | </listitem> |
| 621 | </varlistentry> |
| 622 | <varlistentry> |
| 623 | <term>601 Configuration</term> |
| 624 | <listitem> |
| 625 | <para> |
| 626 | APT is sending the configuration space to the method. A series of Config-Item |
| 627 | fields will be part of this message, each containing an entry from the |
| 628 | configuration space. Fields: Config-Item. |
| 629 | </para> |
| 630 | </listitem> |
| 631 | </varlistentry> |
| 632 | <varlistentry> |
| 633 | <term>602 Authorization Credentials</term> |
| 634 | <listitem> |
| 635 | <para> |
| 636 | This is sent in response to a <emphasis>402 Authorization Required</emphasis> |
| 637 | message. It contains the entered username and password. Fields: Site, User, |
| 638 | Password |
| 639 | </para> |
| 640 | </listitem> |
| 641 | </varlistentry> |
| 642 | <varlistentry> |
| 643 | <term>603 Media Changed</term> |
| 644 | <listitem> |
| 645 | <para> |
| 646 | This is sent in response to a <emphasis>403 Media Failure</emphasis> |
| 647 | message. It indicates that the user has changed media and it is safe |
| 648 | to proceed. Fields: Media, Fail |
| 649 | </para> |
| 650 | </listitem> |
| 651 | </varlistentry> |
| 652 | </variablelist> |
| 653 | </section> |
| 654 | |
| 655 | <section id="s2.4"><title>Notes</title> |
| 656 | <para> |
| 657 | The methods supplied by the stock apt are: |
| 658 | </para> |
| 659 | <orderedlist numeration="arabic"> |
| 660 | <listitem> |
| 661 | <para> |
| 662 | cdrom - For Multi-Disc CD-ROMs |
| 663 | </para> |
| 664 | </listitem> |
| 665 | <listitem> |
| 666 | <para> |
| 667 | copy - (internal) For copying files around the filesystem |
| 668 | </para> |
| 669 | </listitem> |
| 670 | <listitem> |
| 671 | <para> |
| 672 | file - For local files |
| 673 | </para> |
| 674 | </listitem> |
| 675 | <listitem> |
| 676 | <para> |
| 677 | gzip - (internal) For decompression |
| 678 | </para> |
| 679 | </listitem> |
| 680 | <listitem> |
| 681 | <para> |
| 682 | http - For HTTP servers |
| 683 | </para> |
| 684 | </listitem> |
| 685 | </orderedlist> |
| 686 | <para> |
| 687 | The two internal methods, copy and gzip, are used by the acquire code to |
| 688 | parallize and simplify the automatic decompression of package files as well as |
| 689 | copying package files around the file system. Both methods can be seen to act |
| 690 | the same except that one decompresses on the fly. APT uses them by generating |
| 691 | a copy URI that is formed identically to a file URI. The destination file is |
| 692 | send as normal. The method then takes the file specified by the URI and writes |
| 693 | it to the destination file. A typical set of operations may be: |
| 694 | </para> |
| 695 | <screen> |
| 696 | http://foo.com/Packages.gz -> /bar/Packages.gz |
| 697 | gzip:/bar/Packages.gz -> /bar/Packages.decomp |
| 698 | rename Packages.decomp to /final/Packages |
| 699 | </screen> |
| 700 | <para> |
| 701 | The http method implements a fully featured HTTP/1.1 client that supports |
| 702 | deep pipelining and reget. It works best when coupled with an apache 1.3 |
| 703 | server. The file method simply generates failures or success responses |
| 704 | with the filename field set to the proper location. The cdrom method acts |
| 705 | the same except that it checks that the mount point has a valid cdrom in |
| 706 | it. It does this by (effectively) computing a md5 hash of 'ls -l' on the |
| 707 | mountpoint. |
| 708 | </para> |
| 709 | </section> |
| 710 | |
| 711 | </chapter> |
| 712 | |
| 713 | </book> |