1 <!DOCTYPE Article PUBLIC "-//OASIS//DTD DocBook V4.1//EN"> 2 3 <Article> 4 5 <ArticleInfo> 6 7 <Title>EXT2ED - The Extended-2 filesystem editor - User's guide</Title> 8 <AUTHOR> 9 <FirstName>Gadi Oxman, tgud (a] tochnapc2.technion.ac.il</FirstName> 10 </AUTHOR> 11 <PubDate>v0.1, August 3 1995</PubDate> 12 13 <Abstract> 14 15 <Para> 16 This is only the initial version of this document. It may be unclear at 17 some places. Please send me feedback with anything regarding to it. 18 </Para> 19 20 </Abstract> 21 22 </ArticleInfo> 23 24 <Sect1> 25 <Title>About EXT2ED documentation</Title> 26 27 <Para> 28 The EXT2ED documentation consists of three parts: 29 30 <ItemizedList> 31 <ListItem> 32 33 <Para> 34 The ext2 filesystem overview. 35 </Para> 36 </ListItem> 37 <ListItem> 38 39 <Para> 40 The EXT2ED user's guide. 41 </Para> 42 </ListItem> 43 <ListItem> 44 45 <Para> 46 The EXT2ED design and implementation. 47 </Para> 48 </ListItem> 49 50 </ItemizedList> 51 52 </Para> 53 54 <Para> 55 If you intend to used EXT2ED, I strongly suggest that you would be familiar 56 with the material presented in the <Literal remap="tt">ext2 filesystem overview</Literal> as well. 57 </Para> 58 59 <Para> 60 If you also intend to browse and modify the source code, I suggest that you 61 will also read the article <Literal remap="tt">The EXT2ED design and implementation</Literal>, as it 62 provides a general overview of the structure of my source code. 63 </Para> 64 65 </Sect1> 66 67 <Sect1> 68 <Title>Introduction</Title> 69 70 <Para> 71 EXT2ED is a "disk editor" for the ext2 filesystem. Its purpose is to show 72 you the internal structures of the ext2 filesystem in an rather intuitive 73 and logical way, so that it will be easier to "travel" between the various 74 internal filesystem structures. 75 </Para> 76 77 </Sect1> 78 79 <Sect1> 80 <Title>Basic concepts in EXT2ED</Title> 81 82 <Para> 83 Two basic concepts in EXT2ED are <Literal remap="tt">commands</Literal> and <Literal remap="tt">types</Literal>. 84 </Para> 85 86 <Para> 87 EXT2ED is object-oriented in the sense that it defines objects in the 88 filesystem, like a <Literal remap="tt">super-block</Literal> or a <Literal remap="tt">directory</Literal>. An object is 89 something which "knows" how to handle some aspect of the filesystem. 90 </Para> 91 92 <Para> 93 Your interaction with EXT2ED is done through <Literal remap="tt">commands</Literal> which EXT2ED 94 accepts. There are three levels of commands: 95 96 <ItemizedList> 97 <ListItem> 98 99 <Para> 100 General Commands 101 </Para> 102 </ListItem> 103 <ListItem> 104 105 <Para> 106 Extended-2 Filesystem general commands 107 </Para> 108 </ListItem> 109 <ListItem> 110 111 <Para> 112 Type specific commands 113 </Para> 114 </ListItem> 115 116 </ItemizedList> 117 118 The General commands are always available. 119 </Para> 120 121 <Para> 122 The ext2 general commands are available only when editing an ext2 filesystem. 123 </Para> 124 125 <Para> 126 The Type specific commands are available when editing a specific object in the 127 filesystem. Each object typically comes with its own set of internal 128 variables, and its own set of commands, which are fine tuned handle the 129 corresponding structure in the filesystem. 130 </Para> 131 132 </Sect1> 133 134 <Sect1> 135 <Title>Running EXT2ED</Title> 136 137 <Para> 138 Running EXT2ED is as simple as typing <Literal remap="tt">ext2ed</Literal> from the shell prompt. 139 There are no command line switches. 140 </Para> 141 142 <Para> 143 When first run, EXT2ED parses its configuration file, <Literal remap="tt">ext2ed.conf</Literal>. 144 This file must exist. 145 </Para> 146 147 <Para> 148 When the configuration file processing is done, EXT2ED screen should appear 149 on the screen, with the command prompt <Literal remap="tt">ext2ed></Literal> displayed. 150 </Para> 151 152 </Sect1> 153 154 <Sect1> 155 <Title>EXT2ED user interface</Title> 156 157 <Para> 158 EXT2ED uses the <Emphasis>ncurses</Emphasis> library for screen management. Your screen 159 will be divided into four parts, from top to bottom: 160 161 <ItemizedList> 162 <ListItem> 163 164 <Para> 165 Title window 166 </Para> 167 </ListItem> 168 <ListItem> 169 170 <Para> 171 Status window 172 </Para> 173 </ListItem> 174 <ListItem> 175 176 <Para> 177 Main editing window 178 </Para> 179 </ListItem> 180 <ListItem> 181 182 <Para> 183 Command window 184 </Para> 185 </ListItem> 186 187 </ItemizedList> 188 189 The title window just displays the current version of EXT2ED. 190 </Para> 191 192 <Para> 193 The status window will display various information regarding the state of 194 the editing at this point. 195 </Para> 196 197 <Para> 198 The main editing window is the place at which the actual data will be shown. 199 Almost every command will cause some display at this window. This window, as 200 opposed to the three others, is of variable length - You always look at one 201 page of it. The current page and the total numbers of pages at this moment 202 is displayed at the status window. Moving between pages is done by the use 203 of the <Command>pgdn</Command> and <Command>pgup</Command> commands. 204 </Para> 205 206 <Para> 207 The command window is at the bottom of the screen. It always displays a 208 command prompt <Literal remap="tt">ext2ed></Literal> and allows you to type a command. Feedback 209 about the commands entered is displayed to this window also. 210 </Para> 211 212 <Para> 213 EXT2ED uses the <Emphasis>readline</Emphasis> library while processing a command line. All 214 the usual editing keys are available. Each entered command is placed into a 215 history of commands, and can be recalled later. Command Completion is also 216 supported - Just start to type a command, and press the completion key. 217 </Para> 218 219 <Para> 220 Pressing <Literal remap="tt">enter</Literal> at the command window, without entering a command, 221 recalls the last command. This is useful when moving between close entries, 222 in the <Command>next</Command> command, for example. 223 </Para> 224 225 </Sect1> 226 227 <Sect1> 228 <Title>Getting started</Title> 229 230 <Sect2> 231 <Title>A few precautions</Title> 232 233 <Para> 234 EXT2ED is a tool for filesystem <Literal remap="tt">editing</Literal>. As such, it can be 235 <Literal remap="tt">dangerous</Literal>. The summary to the subsections below is that 236 <Literal remap="tt">You must know what you are doing</Literal>. 237 </Para> 238 239 <Sect3 id="mounted-ref"> 240 <Title>A mounted filesystem</Title> 241 242 <Para> 243 EXT2ED is not designed to work on a mounted filesystem - It is complicated 244 enough as it is; I didn't even try to think of handling the various race 245 conditions. As such, please respect the following advice: 246 </Para> 247 248 <Para> 249 <Literal remap="tt">Do not use EXT2ED on a mounted filesystem !</Literal> 250 </Para> 251 252 <Para> 253 EXT2ED will not allow write access to a mounted filesystem. Although it is 254 fairly easy to change EXT2ED so that it will be allowed, I hereby request 255 again- EXT2ED is not designed for that action, and will most likely corrupt 256 data if used that way. Please don't do that. 257 </Para> 258 259 <Para> 260 Concerning read access, I chose to leave the decision for the user through 261 the configuration file option <Literal remap="tt">AllowMountedRead</Literal>. Although read access 262 on a mounted partition will not do any damage to the filesystem, the data 263 displayed to you will not be reliable, and showing you incorrect information 264 may be as bad as corrupting the filesystem. However, you may still wish to 265 do that. 266 </Para> 267 268 </Sect3> 269 270 <Sect3> 271 <Title>Write access</Title> 272 273 <Para> 274 Considering the obvious sensitivity of the subject, I took the following 275 actions: 276 </Para> 277 278 <Para> 279 280 <OrderedList> 281 <ListItem> 282 283 <Para> 284 EXT2ED will always start with a read-only access. Write access mode 285 needs to be specifically entered by the <Command>enablewrite</Command> command. 286 Until this is done, no write will be allowed. Write access can be 287 disabled at any time with <Command>disablewrite</Command>. When 288 <Command>enablewrite</Command> is issued, the device is reopened in read-write 289 mode. Needless to say, the device permissions should allow that. 290 </Para> 291 </ListItem> 292 <ListItem> 293 294 <Para> 295 As a second level of protection, you can disallow write access in 296 the configuration file by using the <Literal remap="tt">AllowChanges off</Literal> 297 configuration option. In this case, the <Command>enablewrite</Command> command 298 will be refused. 299 </Para> 300 </ListItem> 301 <ListItem> 302 303 <Para> 304 When write access is enabled, the data will never change 305 immediately. Rather, a specific <Command>writedata</Command> command is needed 306 to update the object in the disk with the changed object in memory. 307 </Para> 308 </ListItem> 309 <ListItem> 310 311 <Para> 312 In addition, A logging option is provided through the configuration 313 file options <Literal remap="tt">LogChanges</Literal> and <Literal remap="tt">LogFile</Literal>. With logging 314 enabled, each change to the disk will be logged at a very primitive 315 level - A hex dump of the original data and of the new written data. 316 The log file will be a text file which is easily readable, and you 317 can make use of it to undo any changes which you made (EXT2ED doesn't 318 make use of the log file for that purpose, it just logs the changes). 319 </Para> 320 </ListItem> 321 322 </OrderedList> 323 324 Please remember that this is only the initial release of EXT2ED, and it is 325 not very much tested - It is reasonable to assume that <Literal remap="tt">there are 326 bugs</Literal>. 327 However, the logging option above can offer protection even from this 328 unfortunate case. Therefor, I highly recommend that at least when first 329 working with EXT2ED, the logging option will be enabled, despite the disk 330 space which it consumes. 331 </Para> 332 333 </Sect3> 334 335 </Sect2> 336 337 <Sect2 id="help-ref"> 338 <Title>The help command</Title> 339 340 <Para> 341 When loaded, EXT2ED will show a short help screen. This help screen can 342 always be retrieved by the command <Command>help</Command>. The help screen displays a 343 list of all the commands which are available at this point. At startup, only 344 the <Literal remap="tt">General commands</Literal> are available. 345 This will change with time, since each object has its own commands. Thus, 346 commands which are available now may not be available later. 347 Using <Command>help</Command> <Emphasis>command</Emphasis> will display additional information about 348 the specific command <Emphasis>command</Emphasis>. 349 </Para> 350 351 </Sect2> 352 353 <Sect2 id="setdevice-ref"> 354 <Title>The setdevice command</Title> 355 356 <Para> 357 The first command that is usually entered to EXT2ED is the <Command>setdevice</Command> 358 command. This command simply tells EXT2ED on which device the filesystem is 359 present. For example, suppose my ext2 filesystem is on the first partition 360 of my ide disk. The command will be: 361 362 <Screen> 363 setdevice /dev/hda1 364 </Screen> 365 366 The following actions will take place in the following order: 367 368 <OrderedList> 369 <ListItem> 370 371 <Para> 372 EXT2ED will check if the partition is mounted. 373 If the partition is mounted (<Literal remap="tt">highly not recommended</Literal>), 374 the accept/reject behavior will be decided by the configuration 375 file. Cross reference section <XRef LinkEnd="mounted-ref">. 376 </Para> 377 </ListItem> 378 <ListItem> 379 380 <Para> 381 The specified device will be opened in read-only mode. The 382 permissions of the device should be set in a way that allows 383 you to open the device for read access. 384 </Para> 385 </ListItem> 386 <ListItem> 387 388 <Para> 389 Autodetection of an ext2 filesystem will be made by searching for 390 the ext2 magic number in the main superblock. 391 </Para> 392 </ListItem> 393 <ListItem> 394 395 <Para> 396 In the case of a successful recognition of an ext2 filesystem, the 397 ext2 filesystem specific commands and the ext2 specific object 398 definitions will be registered. The object definitions will be read 399 at run time from a file specified by the configuration file. 400 401 In case of a corrupted ext2 filesystem, it is quite possible that 402 the main superblock is damaged and autodetection will fail. In that 403 case, use the configuration option <Literal remap="tt">ForceExt2 on</Literal>. This is not 404 the default case since EXT2ED can be used at a lower level to edit a 405 non-ext2 filesystem. 406 </Para> 407 </ListItem> 408 <ListItem> 409 410 <Para> 411 In a case of a successful autodetection, essential information about 412 the filesystem such as the block size will be read from the 413 superblock, unless the used overrides this behavior with an 414 configuration option (not recommended). In that case, the parameters 415 will be read from the configuration file. 416 417 In a case of an autodetection failure, the essential parameters 418 will be read from the configuration file. 419 </Para> 420 </ListItem> 421 422 </OrderedList> 423 424 Assuming that you are editing an ext2 filesystem and that everything goes 425 well, you will notice that additional commands are now available in the help 426 screen, under the section <Literal remap="tt">ext2 filesystem general commands</Literal>. In 427 addition, EXT2ED now recognizes a few objects which are essential to the 428 editing of an ext2 filesystem. 429 </Para> 430 431 </Sect2> 432 433 </Sect1> 434 435 <Sect1> 436 <Title>Two levels of usage</Title> 437 438 <Sect2> 439 <Title>Low level usage</Title> 440 441 <Para> 442 This section explains what EXT2ED provides even when not editing an ext2 443 filesystem. 444 </Para> 445 446 <Para> 447 Even at this level, EXT2ED is more than just a hex editor. It still allows 448 definition of objects and variables in run time through a user file, 449 although of-course the objects will not have special fine tuned functions 450 connected to them. EXT2ED will allow you to move in the filesystem using 451 <Command>setoffset</Command>, and to apply an object definition on a specific place 452 using <Command>settype</Command> <Emphasis>type</Emphasis>. From this point and on, the object will 453 be shown <Literal remap="tt">in its native form</Literal> - You will see a list of the 454 variables rather than just a hex dump, and you will be able to change each 455 variable in the intuitive form <Command>set variable=value</Command>. 456 </Para> 457 458 <Para> 459 To define objects, use the configuration option <Literal remap="tt">AlternateDescriptors</Literal>. 460 </Para> 461 462 <Para> 463 There are now two forms of editing: 464 465 <ItemizedList> 466 <ListItem> 467 468 <Para> 469 Editing without a type. In this case, the disk block will be shown 470 as a text+hex dump, and you will be able to move along and change it. 471 </Para> 472 </ListItem> 473 <ListItem> 474 475 <Para> 476 Editing with a type. In this case, the object's variables will be 477 shown, and you will be able to change each variable in its native form. 478 </Para> 479 </ListItem> 480 481 </ItemizedList> 482 483 </Para> 484 485 </Sect2> 486 487 <Sect2> 488 <Title>High level usage</Title> 489 490 <Para> 491 EXT2ED was designed for the editing of the ext2 filesystem. As such, it 492 "understands" the filesystem structure to some extent. Each object now has 493 special fine tuned 'C' functions connected to it, which knows how to display 494 it in an intuitive form, and how the object fits in the general design of 495 the ext2 filesystem. It is of-course much easier to use this type of 496 editing. For example: 497 498 <Screen> 499 Issue <Emphasis>group 2</Emphasis> to look at the main copy of the third group block 500 descriptor. With <Emphasis>gocopy 1</Emphasis> you can move to its first backup copy, 501 and with <Emphasis>inode</Emphasis> you can start editing the inode table of the above 502 group block. From here, if the inode corresponds to a file, you can 503 use <Emphasis>file</Emphasis> to edit the file in a "continuous" way, using 504 <Emphasis>nextblock</Emphasis> to pass to its next block, letting EXT2ED following by 505 itself the direct blocks, indirect blocks, ..., while still preserving the 506 actual view of the exact block usage of the file. 507 </Screen> 508 509 The point is that the "tour" of the filesystem will now be synchronic rather 510 than asynchronic - Each object has the "links" to pass between connected 511 logical structures, and special fine-tuned functions to deal with it. 512 </Para> 513 514 </Sect2> 515 516 </Sect1> 517 518 <Sect1> 519 <Title>General commands</Title> 520 521 <Para> 522 I will now start with a systematic explanation of the general commands. 523 Please feel free to experiment, but take care when using the 524 <Literal remap="tt">enablewrite</Literal> command. 525 </Para> 526 527 <Para> 528 Whenever a command syntax is specified, arguments which are optional are 529 enclosed with square brackets. 530 </Para> 531 532 <Para> 533 Please note that in EXT2ED, each command can be overridden by a specific 534 object to provide special fine-tuned functionality. In general, I was 535 attempting to preserve the similarity between those functions, which are 536 accessible by the same name. 537 </Para> 538 539 <Sect2 id="disablewrite-ref"> 540 <Title>disablewrite</Title> 541 542 <Para> 543 544 <Screen> 545 Syntax: disablewrite 546 </Screen> 547 548 <Command>disablewrite</Command> is used to reopen the device with read-only access. When 549 first running EXT2ED, the device is opened in read-only mode, and an 550 explicit <Command>enablewrite</Command> is required for write access. When finishing 551 with changing, a <Command>disablewrite</Command> is recommended for safety. Cross 552 reference section <XRef LinkEnd="disablewrite-ref">. 553 </Para> 554 555 </Sect2> 556 557 <Sect2 id="enablewrite-ref"> 558 <Title>enablewrite</Title> 559 560 <Para> 561 562 <Screen> 563 Syntax: enablewrite 564 </Screen> 565 566 <Command>enablewrite</Command> is used to reopen the device with read-write access. 567 When first running EXT2ED, the device is opened in read-only mode, and an 568 explicit <Command>enablewrite</Command> is required for write access. 569 <Command>enablewrite</Command> will fail if write access is disabled from the 570 configuration file by the <Literal remap="tt">AllowChanges off</Literal> configuration option. 571 Even after <Command>enablewrite</Command>, an explicit <Command>writedata</Command> 572 is required to actually write the new data to the disk. 573 When finishing with changing, a <Command>disablewrite</Command> is recommended for safety. 574 Cross reference section <XRef LinkEnd="enablewrite-ref">. 575 </Para> 576 577 </Sect2> 578 579 <Sect2> 580 <Title>help</Title> 581 582 <Para> 583 584 <Screen> 585 Syntax: help [command] 586 </Screen> 587 588 The <Command>help</Command> command is described at section <XRef LinkEnd="help-ref">. 589 </Para> 590 591 </Sect2> 592 593 <Sect2 id="next-ref"> 594 <Title>next</Title> 595 596 <Para> 597 598 <Screen> 599 Syntax: next [number] 600 </Screen> 601 602 This section describes the <Emphasis>general command</Emphasis> <Command>next</Command>. <Command>next</Command> 603 is overridden by several types in EXT2ED, to provide fine-tuned 604 functionality. 605 </Para> 606 607 <Para> 608 The <Literal remap="tt">next general command</Literal> behavior is depended on whether you are editing a 609 specific object, or none. 610 </Para> 611 612 <Para> 613 614 <ItemizedList> 615 <ListItem> 616 617 <Para> 618 In the case where Type is <Literal remap="tt">none</Literal> (The current type is showed 619 on the status window by the <Command>show</Command> command), <Literal remap="tt">next</Literal> 620 passes to the next <Emphasis>number</Emphasis> bytes in the current edited block. 621 If <Emphasis>number</Emphasis> is not specified, <Emphasis>number=1</Emphasis> is assumed. 622 </Para> 623 </ListItem> 624 <ListItem> 625 626 <Para> 627 In the case where Type is defined, the <Command>next</Command> commands assumes 628 that you are editing an array of objects of that type, and the 629 <Command>next</Command> command will just pass to the next entry in the array. 630 If <Emphasis>number</Emphasis> is defined, it will pass <Emphasis>number</Emphasis> entries 631 ahead. 632 </Para> 633 </ListItem> 634 635 </ItemizedList> 636 637 </Para> 638 639 </Sect2> 640 641 <Sect2 id="pgdn-ref"> 642 <Title>pgdn</Title> 643 644 <Para> 645 646 <Screen> 647 Syntax: pgdn 648 </Screen> 649 650 Usually the edited data doesn't fit into the visible main window. In this 651 case, the status window will indicate that there is more to see "below" by 652 the message <Literal remap="tt">Page x of y</Literal>. This means that there are <Emphasis>y</Emphasis> pages 653 total, and you are currently viewing the <Emphasis>x</Emphasis> page. With the <Command>pgdn</Command> 654 command, you can pass to the next available page. 655 </Para> 656 657 </Sect2> 658 659 <Sect2> 660 <Title>pgup</Title> 661 662 <Para> 663 664 <Screen> 665 Syntax: pgup 666 </Screen> 667 668 </Para> 669 670 <Para> 671 <Command>pgup</Command> is the opposite of <Command>pgdn</Command> - It will pass to the previous 672 page. Cross reference section <XRef LinkEnd="pgdn-ref">. 673 </Para> 674 675 </Sect2> 676 677 <Sect2> 678 <Title>prev</Title> 679 680 <Para> 681 682 <Screen> 683 Syntax: prev [number] 684 </Screen> 685 686 </Para> 687 688 <Para> 689 <Command>prev</Command> is the opposite of <Command>next</Command>. Cross reference section 690 <XRef LinkEnd="next-ref">. 691 </Para> 692 693 </Sect2> 694 695 <Sect2 id="recall-ref"> 696 <Title>recall</Title> 697 698 <Para> 699 700 <Screen> 701 Syntax: recall object 702 </Screen> 703 704 <Command>recall</Command> is the opposite of <Command>remember</Command>. It will place you at the 705 place you where when saving the object position and type information. Cross 706 reference section <XRef LinkEnd="remember-ref">. 707 </Para> 708 709 </Sect2> 710 711 <Sect2> 712 <Title>redraw</Title> 713 714 <Para> 715 716 <Screen> 717 Syntax: redraw 718 </Screen> 719 720 Sometimes the screen display gets corrupted. I still have problems with 721 this. The <Command>redraw</Command> command simply redraws the entire display screen. 722 </Para> 723 724 </Sect2> 725 726 <Sect2 id="remember-ref"> 727 <Title>remember</Title> 728 729 <Para> 730 731 <Screen> 732 Syntax: remember object 733 </Screen> 734 735 EXT2ED provides you <Literal remap="tt">memory</Literal> of objects; While editing, you may reach an 736 object which you will like to return to later. The <Command>remember</Command> command 737 will store in memory the current place and type of the object. You can 738 return to the object by using the <Command>recall</Command> command. Cross reference 739 section <XRef LinkEnd="recall-ref">. 740 </Para> 741 742 <Para> 743 <Literal remap="tt">Note:</Literal> 744 745 <ItemizedList> 746 <ListItem> 747 748 <Para> 749 When remembering a <Literal remap="tt">file</Literal> or a <Literal remap="tt">directory</Literal>, the 750 corresponding inode will be saved in memory. The basic reason is that 751 the inode is essential for finding the blocks of the file or the 752 directory. 753 </Para> 754 </ListItem> 755 756 </ItemizedList> 757 758 </Para> 759 760 </Sect2> 761 762 <Sect2> 763 <Title>set</Title> 764 765 <Para> 766 767 <Screen> 768 Syntax: set [text || hex] arg1 [arg2 arg3 ...] 769 770 or 771 772 Syntax: set variable=value 773 </Screen> 774 775 The <Command>set</Command> command is used to modify the current data. 776 The <Command>set general command</Command> behavior is depended on whether you are editing a 777 specific object, or none. 778 </Para> 779 780 <Para> 781 782 <ItemizedList> 783 <ListItem> 784 785 <Para> 786 In the case where Type is <Command>none</Command>, the first syntax should be 787 used. The set command affects the data starting at the current 788 highlighted position in the edited block. 789 790 <ItemizedList> 791 <ListItem> 792 793 <Para> 794 When using the <Command>set hex</Command> command, a list of 795 hexadecimal bytes should follow. 796 </Para> 797 </ListItem> 798 <ListItem> 799 800 <Para> 801 When using the <Command>set text</Command> command, it should be followed 802 by a text string. 803 </Para> 804 </ListItem> 805 806 </ItemizedList> 807 808 Examples: 809 810 <Screen> 811 set hex 09 0a 0b 0c 0d 0e 0f 812 set text Linux is just great ! 813 814 </Screen> 815 816 </Para> 817 </ListItem> 818 <ListItem> 819 820 <Para> 821 In the case where Type is defined, the second syntax should be used. 822 The set commands just sets the variable <Emphasis>variable</Emphasis> with the 823 value <Emphasis>value</Emphasis>. 824 </Para> 825 </ListItem> 826 827 </ItemizedList> 828 829 In any case, the data is only changed in memory. For an actual update to the 830 disk, use the <Command>writedata</Command> command. 831 </Para> 832 833 </Sect2> 834 835 <Sect2> 836 <Title>setdevice</Title> 837 838 <Para> 839 840 <Screen> 841 Syntax: setdevice device 842 </Screen> 843 844 The <Command>setdevice</Command> command is described at section <XRef LinkEnd="setdevice-ref">. 845 </Para> 846 847 </Sect2> 848 849 <Sect2> 850 <Title>setoffset</Title> 851 852 <Para> 853 854 <Screen> 855 Syntax: setoffset [block || type] [+|-]offset 856 </Screen> 857 858 The <Command>setoffset</Command> command is used to move asynchronically inside the file 859 system. It is considered a low level command, and usually should not be used 860 when editing an ext2 filesystem, simply because movement is better 861 utilized through the specific ext2 commands. 862 </Para> 863 864 <Para> 865 The <Command>offset</Command> is in bytes, and meanwhile should be positive and smaller 866 than 2GB. 867 </Para> 868 869 <Para> 870 Use of the <Command>block</Command> modifier changes the counting unit to block. 871 </Para> 872 873 <Para> 874 Use of the <Literal remap="tt">+ or -</Literal> modifiers signals that the offset is relative to 875 the current position. 876 </Para> 877 878 <Para> 879 use of the <Literal remap="tt">type</Literal> modifier is allowed only with relative offset. This 880 modifier will multiply the offset by the size of the current type. 881 </Para> 882 883 </Sect2> 884 885 <Sect2> 886 <Title>settype</Title> 887 888 <Para> 889 890 <Screen> 891 Syntax: settype type || [none | hex] 892 </Screen> 893 894 The <Command>settype</Command> command is used to move apply the object definitions of 895 the type <Emphasis>type</Emphasis> on the current position. It is considered a low level 896 command and usually should not be used when editing an ext2 filesystem since 897 EXT2ED provides better tools. It is of-course very useful when editing a 898 non-ext2 filesystem and using user-defined objects. 899 </Para> 900 901 <Para> 902 When <Emphasis>type</Emphasis> is <Emphasis>hex</Emphasis> or <Emphasis>none</Emphasis>, the data will be displayed as 903 a hex and text dump. 904 </Para> 905 906 </Sect2> 907 908 <Sect2> 909 <Title>show</Title> 910 911 <Para> 912 913 <Screen> 914 Syntax: show 915 </Screen> 916 917 The <Command>show</Command> command will show the data of the current object at the 918 current position on the main display window. It will also update the status 919 window with type specific information. It may be necessary to use 920 <Command>pgdn</Command> and <Command>pgup</Command> to view the entire data. 921 </Para> 922 923 </Sect2> 924 925 <Sect2> 926 <Title>writedata</Title> 927 928 <Para> 929 930 <Screen> 931 Syntax: writedata 932 </Screen> 933 934 The <Command>writedata</Command> command will update the disk with the object data that 935 is currently in memory. This is the point at which actual change is made to 936 the filesystem. Without this command, the edited data will not have any 937 effect. Write access should be allowed for a successful update. 938 </Para> 939 940 </Sect2> 941 942 </Sect1> 943 944 <Sect1> 945 <Title>Editing an ext2 filesystem</Title> 946 947 <Para> 948 In order to edit an ext2 filesystem, you should, of course, know the structure 949 of the ext2 filesystem. If you feel that you lack some knowledge in this 950 area, I suggest that you do some of the following: 951 952 <ItemizedList> 953 <ListItem> 954 955 <Para> 956 Read the supplied ext2 technical information. I tried to summarize 957 the basic information which is needed to get you started. 958 </Para> 959 </ListItem> 960 <ListItem> 961 962 <Para> 963 Get the slides that Remy Card (The author of the ext2 filesystem) 964 prepared concerning the ext2 filesystem. 965 </Para> 966 </ListItem> 967 <ListItem> 968 969 <Para> 970 Read the kernel sources. 971 </Para> 972 </ListItem> 973 974 </ItemizedList> 975 976 At this point, you should be familiar with the following terms: 977 <Literal remap="tt">block, inode, superblock, block groups, block allocation bitmap, inode 978 allocation bitmap, group descriptors, file, directory.</Literal>Most of the above 979 are objects in EXT2ED. 980 </Para> 981 982 <Para> 983 When editing an ext2 filesystem it is recommended that you use the ext2 984 specific commands, rather then the general commands <Command>setoffset</Command> and 985 <Command>settype</Command>, mainly because: 986 987 <OrderedList> 988 <ListItem> 989 990 <Para> 991 In most cases it will be unreliable, and will display incorrect 992 information. 993 994 Sometimes in order to edit an object, EXT2ED needs the information 995 of some other related objects. For example, when editing a 996 directory, EXT2ED needs access to the inode of the edited directory. 997 Simply setting the type to a directory <Literal remap="tt">will be unreliable</Literal>, 998 since the object assumes that you passed through its inode to reach 999 it, and expects this information, which isn't initialized if you 1000 directly set the type to a directory. 1001 </Para> 1002 </ListItem> 1003 <ListItem> 1004 1005 <Para> 1006 EXT2ED offers far better tools for handling the ext2 filesystem 1007 using the ext2 specific commands. 1008 </Para> 1009 </ListItem> 1010 1011 </OrderedList> 1012 1013 </Para> 1014 1015 </Sect1> 1016 1017 <Sect1> 1018 <Title>ext2 general commands</Title> 1019 1020 <Para> 1021 The <Literal remap="tt">ext2 general commands</Literal> are available only when you are editing an 1022 ext2 filesystem. They are <Literal remap="tt">general</Literal> in the sense that they are not 1023 specific to some object, and can be invoked anytime. 1024 </Para> 1025 1026 <Sect2 id="general-superblock"> 1027 <Title>super</Title> 1028 1029 <Para> 1030 1031 <Screen> 1032 Syntax: super 1033 </Screen> 1034 1035 The <Command>super</Command> command will "bring you" to the main superblock copy. It 1036 will automatically set the object type to <Literal remap="tt">ext2_super_block</Literal>. Then you 1037 will be able to view and edit the superblock. When you are in the 1038 superblock, other commands will be available. 1039 </Para> 1040 1041 </Sect2> 1042 1043 <Sect2> 1044 <Title>group</Title> 1045 1046 <Para> 1047 1048 <Screen> 1049 Syntax: group [number] 1050 </Screen> 1051 1052 The <Command>group</Command> command will "bring you" to the main copy of the 1053 <Emphasis>number</Emphasis> group descriptor. It will automatically set the object type to 1054 <Literal remap="tt">ext2_group_desc</Literal>. Then you will be able to view and edit the group 1055 descriptor entry. When you are there, other commands will be available. 1056 </Para> 1057 1058 </Sect2> 1059 1060 <Sect2> 1061 <Title>cd</Title> 1062 1063 <Para> 1064 1065 <Screen> 1066 Syntax: cd path 1067 </Screen> 1068 1069 The <Command>cd</Command> command will let you travel in the filesystem in the nice way 1070 that the mounted filesystem would have let you. 1071 </Para> 1072 1073 <Para> 1074 The <Command>cd</Command> command is a complicated command. Although it may sound 1075 simple at first, an implementation of a typical cd requires passing through 1076 the group descriptors, inodes, directory entries, etc. For example: 1077 </Para> 1078 1079 <Para> 1080 The innocent cd /usr command can be done by using more primitive 1081 EXT2ED commands in the following way (It is implemented exactly this way): 1082 1083 <OrderedList> 1084 <ListItem> 1085 1086 <Para> 1087 Using <Command>group 0</Command> to go to the first group descriptor. 1088 </Para> 1089 </ListItem> 1090 <ListItem> 1091 1092 <Para> 1093 Using <Command>inode</Command> to get to the Bad blocks inode. 1094 </Para> 1095 </ListItem> 1096 <ListItem> 1097 1098 <Para> 1099 Using <Command>next</Command> to pass to the root directory inode. 1100 </Para> 1101 </ListItem> 1102 <ListItem> 1103 1104 <Para> 1105 Using <Command>dir</Command> to see the directory. 1106 </Para> 1107 </ListItem> 1108 <ListItem> 1109 1110 <Para> 1111 Using <Command>next</Command> until we find the directory usr. 1112 </Para> 1113 </ListItem> 1114 <ListItem> 1115 1116 <Para> 1117 Using <Command>followinode</Command> to pass to the inode corresponding to usr. 1118 </Para> 1119 </ListItem> 1120 <ListItem> 1121 1122 <Para> 1123 Using <Command>dir</Command> to see the directory of /usr. 1124 </Para> 1125 </ListItem> 1126 1127 </OrderedList> 1128 1129 And those commands aren't that primitive; For example, the tracing of the 1130 blocks which belong to the root directory is done automatically by the dir 1131 command behind the scenes, and the followinode command will automatically 1132 "run" to the correct group descriptor in order to find the required inode. 1133 </Para> 1134 1135 <Para> 1136 The path to the <Command>general cd</Command> command needs to be a full pathname - 1137 Starting from <Filename>/</Filename>. The <Command>cd</Command> command stops at the last reachable 1138 point, which can be a directory entry, in which case the type will be set to 1139 <Literal remap="tt">dir</Literal>, or an inode, in which case the type will be set to 1140 <Literal remap="tt">ext2_inode</Literal>. Symbolic links (Only fast symbolic links, meanwhile) are 1141 automatically followed (if they are not across filesystems, of-course). If 1142 the type is set to <Literal remap="tt">dir</Literal>, you can use a path relative to the 1143 "current directory". 1144 </Para> 1145 1146 </Sect2> 1147 1148 </Sect1> 1149 1150 <Sect1> 1151 <Title>The superblock</Title> 1152 1153 <Para> 1154 The superblock can always be reached by the ext2 general command 1155 <Command>super</Command>. Cross reference section <XRef LinkEnd="general-superblock">. 1156 </Para> 1157 1158 <Para> 1159 The status window will show you which copy of the superblock copies you are 1160 currently editing. 1161 </Para> 1162 1163 <Para> 1164 The main data window will show you the values of the various superblock 1165 variables, along with some interpretation of the values. 1166 </Para> 1167 1168 <Para> 1169 Data can be changed with the <Command>set</Command> and <Command>writedata</Command> commands. 1170 1171 <Screen> 1172 For example, set s_r_blocks_count=1400 will reserve 1400 blocks for root. 1173 </Screen> 1174 1175 </Para> 1176 1177 <Sect2> 1178 <Title>gocopy</Title> 1179 1180 <Para> 1181 1182 <Screen> 1183 Syntax: gocopy number 1184 </Screen> 1185 1186 The <Command>gocopy</Command> command will "bring you" to the backup copy <Emphasis>number</Emphasis> 1187 of the superblock copies. <Command>gocopy 0</Command>, for example, will bring you to 1188 the main copy. 1189 </Para> 1190 1191 </Sect2> 1192 1193 <Sect2> 1194 <Title>setactivecopy</Title> 1195 1196 <Para> 1197 1198 <Screen> 1199 Syntax: setactivecopy 1200 </Screen> 1201 1202 The <Command>setactivecopy</Command> command will copy the contents of the current 1203 superblock copy onto the contents of the main copy. It will also switch to 1204 editing of the main copy. No actual data is written to disk, of-course, 1205 until you issue the <Command>writedata</Command> command. 1206 </Para> 1207 1208 </Sect2> 1209 1210 </Sect1> 1211 1212 <Sect1> 1213 <Title>The group descriptors</Title> 1214 1215 <Para> 1216 The group descriptors can be edited by the <Command>group</Command> command. 1217 </Para> 1218 1219 <Para> 1220 The status window will indicate the current group descriptor, the total 1221 number of group descriptors (and hence of group blocks), and the backup copy 1222 number. 1223 </Para> 1224 1225 <Para> 1226 The main data window will just show you the values of the various variables. 1227 </Para> 1228 1229 <Para> 1230 Basically, you can use the <Command>next</Command> and <Command>prev</Command> commands, along with the 1231 <Command>set</Command> command, to modify the group descriptors. 1232 </Para> 1233 1234 <Para> 1235 The group descriptors object is a junction, from which you can reach: 1236 1237 <ItemizedList> 1238 <ListItem> 1239 1240 <Para> 1241 The inode table of the corresponding block group (the <Literal remap="tt">inode</Literal> 1242 command) 1243 </Para> 1244 </ListItem> 1245 <ListItem> 1246 1247 <Para> 1248 The block allocation bitmap (the <Literal remap="tt">blockbitmap</Literal> command) 1249 </Para> 1250 </ListItem> 1251 <ListItem> 1252 1253 <Para> 1254 The inode allocation bitmap (the <Literal remap="tt">inodebitmap</Literal> command) 1255 </Para> 1256 </ListItem> 1257 1258 </ItemizedList> 1259 1260 </Para> 1261 1262 <Sect2> 1263 <Title>blockbitmap</Title> 1264 1265 <Para> 1266 1267 <Screen> 1268 Syntax: blockbitmap 1269 </Screen> 1270 1271 The <Command>blockbitmap</Command> command will let you edit the block bitmap allocation 1272 block of the current group block. 1273 </Para> 1274 1275 </Sect2> 1276 1277 <Sect2> 1278 <Title>entry</Title> 1279 1280 <Para> 1281 1282 <Screen> 1283 Syntax: entry number 1284 </Screen> 1285 1286 The <Command>entry</Command> command will move you to the <Emphasis>number</Emphasis> group descriptor in the 1287 group descriptors table. 1288 </Para> 1289 1290 </Sect2> 1291 1292 <Sect2> 1293 <Title>inode</Title> 1294 1295 <Para> 1296 1297 <Screen> 1298 Syntax: inode 1299 </Screen> 1300 1301 The <Command>inode</Command> command will pass you to the first inode in the current 1302 group block. 1303 </Para> 1304 1305 </Sect2> 1306 1307 <Sect2> 1308 <Title>inodebitmap</Title> 1309 1310 <Para> 1311 1312 <Screen> 1313 Syntax: inodebitmap 1314 </Screen> 1315 1316 The <Command>inodebitmap</Command> command will let you edit the inode bitmap allocation 1317 block of the current group block. 1318 </Para> 1319 1320 </Sect2> 1321 1322 <Sect2> 1323 <Title>next</Title> 1324 1325 <Para> 1326 1327 <Screen> 1328 Syntax: next [number] 1329 </Screen> 1330 1331 The <Command>next</Command> command will pass to the next <Emphasis>number</Emphasis> group 1332 descriptor. If <Emphasis>number</Emphasis> is omitted, <Emphasis>number=1</Emphasis> is assumed. 1333 </Para> 1334 1335 </Sect2> 1336 1337 <Sect2> 1338 <Title>prev</Title> 1339 1340 <Para> 1341 1342 <Screen> 1343 Syntax: prev [number] 1344 </Screen> 1345 1346 The <Command>prev</Command> command will pass to the previous <Emphasis>number</Emphasis> group 1347 descriptor. If <Emphasis>number</Emphasis> is omitted, <Emphasis>number=1</Emphasis> is assumed. 1348 </Para> 1349 1350 </Sect2> 1351 1352 <Sect2> 1353 <Title>setactivecopy</Title> 1354 1355 <Para> 1356 1357 <Screen> 1358 Syntax: setactivecopy 1359 </Screen> 1360 1361 The <Command>setactivecopy</Command> command copies the contents of the current group 1362 descriptor, to its main copy. The updated main copy will then be shown. No 1363 actual change is made to the disk until you issue the <Command>writedata</Command> 1364 command. 1365 </Para> 1366 1367 </Sect2> 1368 1369 </Sect1> 1370 1371 <Sect1> 1372 <Title>The inode</Title> 1373 1374 <Para> 1375 An inode can be reached by the following two ways: 1376 1377 <ItemizedList> 1378 <ListItem> 1379 1380 <Para> 1381 Using <Command>inode</Command> from the corresponding group descriptor. 1382 </Para> 1383 </ListItem> 1384 <ListItem> 1385 1386 <Para> 1387 Using <Command>followinode</Command> from a directory entry. 1388 </Para> 1389 </ListItem> 1390 <ListItem> 1391 1392 <Para> 1393 Using the <Command>cd</Command> command with the pathname to the file. 1394 1395 For example, <Command>cd /usr/src/ext2ed/ext2ed.h</Command> 1396 </Para> 1397 </ListItem> 1398 1399 </ItemizedList> 1400 1401 </Para> 1402 1403 <Para> 1404 The status window will indicate: 1405 1406 <ItemizedList> 1407 <ListItem> 1408 1409 <Para> 1410 The current global inode number. 1411 </Para> 1412 </ListItem> 1413 <ListItem> 1414 1415 <Para> 1416 The total total number of inodes. 1417 </Para> 1418 </ListItem> 1419 <ListItem> 1420 1421 <Para> 1422 On which block group the inode is allocated. 1423 </Para> 1424 </ListItem> 1425 <ListItem> 1426 1427 <Para> 1428 The total number of inodes in this group block. 1429 </Para> 1430 </ListItem> 1431 <ListItem> 1432 1433 <Para> 1434 The index of the current inode in the current group block. 1435 </Para> 1436 </ListItem> 1437 <ListItem> 1438 1439 <Para> 1440 The type of the inode (file, directory, special, etc). 1441 </Para> 1442 </ListItem> 1443 1444 </ItemizedList> 1445 1446 </Para> 1447 1448 <Para> 1449 The main data window, in addition to the list of variables, will contain 1450 some interpretations on the right side. 1451 </Para> 1452 1453 <Para> 1454 If the inode corresponds to a file, you can use the <Command>file</Command> command to 1455 edit the file. 1456 </Para> 1457 1458 <Para> 1459 If the inode is an inode of a directory, you can use the <Command>dir</Command> command 1460 to edit the directory. 1461 </Para> 1462 1463 <Sect2> 1464 <Title>dir</Title> 1465 1466 <Para> 1467 1468 <Screen> 1469 Syntax: dir 1470 </Screen> 1471 1472 If the inode mode corresponds to a directory (shown on the status window), 1473 you can enter directory mode editing by using <Literal remap="tt">dir</Literal>. 1474 </Para> 1475 1476 </Sect2> 1477 1478 <Sect2> 1479 <Title>entry</Title> 1480 1481 <Para> 1482 1483 <Screen> 1484 Syntax: entry number 1485 </Screen> 1486 1487 The <Command>entry</Command> command will move you to the <Emphasis>number</Emphasis> inode in the 1488 current inode table. 1489 </Para> 1490 1491 </Sect2> 1492 1493 <Sect2> 1494 <Title>file</Title> 1495 1496 <Para> 1497 1498 <Screen> 1499 Syntax: file 1500 </Screen> 1501 1502 If the inode mode corresponds to a file (shown on the status window), 1503 you can enter file mode editing by using <Command>file</Command>. 1504 </Para> 1505 1506 </Sect2> 1507 1508 <Sect2> 1509 <Title>group</Title> 1510 1511 <Para> 1512 1513 <Screen> 1514 Syntax: group 1515 </Screen> 1516 1517 The <Command>group</Command> command is used to go to the group descriptor of the 1518 current group block. 1519 </Para> 1520 1521 </Sect2> 1522 1523 <Sect2> 1524 <Title>next</Title> 1525 1526 <Para> 1527 1528 <Screen> 1529 Syntax: next [number] 1530 </Screen> 1531 1532 The <Command>next</Command> command will pass to the next <Emphasis>number</Emphasis> inode. 1533 If <Emphasis>number</Emphasis> is omitted, <Emphasis>number=1</Emphasis> is assumed. 1534 </Para> 1535 1536 </Sect2> 1537 1538 <Sect2> 1539 <Title>prev</Title> 1540 1541 <Para> 1542 1543 <Screen> 1544 Syntax: prev [number] 1545 </Screen> 1546 1547 The <Command>prev</Command> command will pass to the previous <Emphasis>number</Emphasis> inode. 1548 If <Emphasis>number</Emphasis> is omitted, <Emphasis>number=1</Emphasis> is assumed. 1549 </Para> 1550 1551 </Sect2> 1552 1553 </Sect1> 1554 1555 <Sect1> 1556 <Title>The file</Title> 1557 1558 <Para> 1559 When editing a file, EXT2ED offers you a both a continuous and a true 1560 fragmented view of the file - The file is still shown block by block with 1561 the true block number at each stage and EXT2ED offers you commands which 1562 allow you to move between the <Literal remap="tt">file blocks</Literal>, while finding the 1563 allocated blocks by using the inode information behind the scenes. 1564 </Para> 1565 1566 <Para> 1567 Aside from this, the editing is just a <Literal remap="tt">hex editing</Literal> - You move the 1568 cursor in the current block of the file by using <Command>next</Command> and 1569 <Command>prev</Command>, move between blocks by <Command>nextblock</Command> and <Command>prevblock</Command>, 1570 and make changes by the <Command>set</Command> command. Note that the set command is 1571 overridden here - There are no variables. The <Command>writedata</Command> command will 1572 update the current block to the disk. 1573 </Para> 1574 1575 <Para> 1576 Reaching a file can be done by using the <Command>file</Command> command from its inode. 1577 The inode can be reached by any other means, for example, by the 1578 <Command>cd</Command> command, if you know the file name. 1579 </Para> 1580 1581 <Para> 1582 The status window will indicate: 1583 1584 <ItemizedList> 1585 <ListItem> 1586 1587 <Para> 1588 The global block number. 1589 </Para> 1590 </ListItem> 1591 <ListItem> 1592 1593 <Para> 1594 The internal file block number. 1595 </Para> 1596 </ListItem> 1597 <ListItem> 1598 1599 <Para> 1600 The file offset. 1601 </Para> 1602 </ListItem> 1603 <ListItem> 1604 1605 <Para> 1606 The file size. 1607 </Para> 1608 </ListItem> 1609 <ListItem> 1610 1611 <Para> 1612 The file inode number. 1613 </Para> 1614 </ListItem> 1615 <ListItem> 1616 1617 <Para> 1618 The indirection level - Whether it is a direct block (0), indirect 1619 (1), etc. 1620 </Para> 1621 </ListItem> 1622 1623 </ItemizedList> 1624 1625 </Para> 1626 1627 <Para> 1628 The main data window will display the file either in hex mode or in text 1629 mode, select-able by the <Command>display</Command> command. 1630 </Para> 1631 1632 <Para> 1633 In hex mode, EXT2ED will display offsets in the current block, along with a 1634 text and hex dump of the current block. 1635 </Para> 1636 1637 <Para> 1638 In either case the <Literal remap="tt">current place</Literal> will be highlighted. In the hex mode 1639 it will be always highlighted, while in the text mode it will be highlighted 1640 if the character is display-able. 1641 </Para> 1642 1643 <Sect2> 1644 <Title>block</Title> 1645 1646 <Para> 1647 1648 <Screen> 1649 Syntax: block block_num 1650 </Screen> 1651 1652 The <Command>block</Command> command is used to move inside the file. The 1653 <Emphasis>block_num</Emphasis> argument is the requested internal file block number. A 1654 value of 0 will reach the beginning of the file. 1655 </Para> 1656 1657 </Sect2> 1658 1659 <Sect2> 1660 <Title>display</Title> 1661 1662 <Para> 1663 1664 <Screen> 1665 Syntax: display [text || hex] 1666 </Screen> 1667 1668 The <Command>display</Command> command changes the display mode of the file. 1669 <Command>display 1670 hex</Command> will switch to <Command>hex mode</Command>, while <Command>display text</Command> will switch 1671 to text mode. The default mode when no <Command>display</Command> command is issued is 1672 <Command>hex mode</Command>. 1673 </Para> 1674 1675 </Sect2> 1676 1677 <Sect2> 1678 <Title>inode</Title> 1679 1680 <Para> 1681 1682 <Screen> 1683 Syntax: inode 1684 </Screen> 1685 1686 The <Command>inode</Command> command will return to the inode of the current file. 1687 </Para> 1688 1689 </Sect2> 1690 1691 <Sect2> 1692 <Title>next</Title> 1693 1694 <Para> 1695 1696 <Screen> 1697 Syntax: next [num] 1698 </Screen> 1699 1700 The <Command>next</Command> command will pass to the next byte in the file. If 1701 <Emphasis>num</Emphasis> is supplied, it will pass to the next <Emphasis>num</Emphasis> bytes. 1702 </Para> 1703 1704 </Sect2> 1705 1706 <Sect2> 1707 <Title>nextblock</Title> 1708 1709 <Para> 1710 1711 <Screen> 1712 Syntax: nextblock [num] 1713 </Screen> 1714 1715 The <Command>nextblock</Command> command will pass to the next block in the file. If 1716 <Emphasis>num</Emphasis> is supplied, it will pass to the next <Emphasis>num</Emphasis> blocks. 1717 </Para> 1718 1719 </Sect2> 1720 1721 <Sect2> 1722 <Title>prev</Title> 1723 1724 <Para> 1725 1726 <Screen> 1727 Syntax: prev [num] 1728 </Screen> 1729 1730 The <Command>prev</Command> command will pass to the previous byte in the file. If 1731 <Emphasis>num</Emphasis> is supplied, it will pass to the previous <Emphasis>num</Emphasis> bytes. 1732 </Para> 1733 1734 </Sect2> 1735 1736 <Sect2> 1737 <Title>prevblock</Title> 1738 1739 <Para> 1740 1741 <Screen> 1742 Syntax: prevblock [num] 1743 </Screen> 1744 1745 The <Command>nextblock</Command> command will pass to the previous block in the file. If 1746 <Emphasis>num</Emphasis> is supplied, it will pass to the previous <Emphasis>num</Emphasis> blocks. 1747 </Para> 1748 1749 </Sect2> 1750 1751 <Sect2> 1752 <Title>offset</Title> 1753 1754 <Para> 1755 1756 <Screen> 1757 Syntax: offset file_offset 1758 </Screen> 1759 1760 The <Command>offset</Command> command will move to the specified offset in the file. 1761 </Para> 1762 1763 </Sect2> 1764 1765 <Sect2> 1766 <Title>set</Title> 1767 1768 <Para> 1769 1770 <Screen> 1771 Syntax: set [text || hex] arg1 [arg2 arg3 ...] 1772 </Screen> 1773 1774 The <Command>file set</Command> command is working like the <Literal remap="tt">general set command</Literal>, 1775 with <Literal remap="tt">type=none</Literal>. There are no variables. 1776 </Para> 1777 1778 </Sect2> 1779 1780 <Sect2> 1781 <Title>writedata</Title> 1782 1783 <Para> 1784 1785 <Screen> 1786 Syntax: writedata 1787 </Screen> 1788 1789 The <Command>writedata</Command> command will update the current file block in the disk. 1790 </Para> 1791 1792 </Sect2> 1793 1794 </Sect1> 1795 1796 <Sect1> 1797 <Title>The directory</Title> 1798 1799 <Para> 1800 When editing a file, EXT2ED analyzes for you both the allocation blocks of 1801 the directory entries, and the directory entries. 1802 </Para> 1803 1804 <Para> 1805 Each directory entry is displayed on one row. You can move the highlighted 1806 entry with the usual <Command>next</Command> and <Command>prev</Command> commands, and "dive in" 1807 with the <Command>followinode</Command> command. 1808 </Para> 1809 1810 <Para> 1811 The status window will indicate: 1812 1813 <ItemizedList> 1814 <ListItem> 1815 1816 <Para> 1817 The directory entry number. 1818 </Para> 1819 </ListItem> 1820 <ListItem> 1821 1822 <Para> 1823 The total number of directory entries in this directory. 1824 </Para> 1825 </ListItem> 1826 <ListItem> 1827 1828 <Para> 1829 The current global block number. 1830 </Para> 1831 </ListItem> 1832 <ListItem> 1833 1834 <Para> 1835 The current offset in the entire directory - When viewing the 1836 directory as a continuous file. 1837 </Para> 1838 </ListItem> 1839 <ListItem> 1840 1841 <Para> 1842 The inode number of the directory itself. 1843 </Para> 1844 </ListItem> 1845 <ListItem> 1846 1847 <Para> 1848 The indirection level - Whether it is a direct block (0), indirect 1849 (1), etc. 1850 </Para> 1851 </ListItem> 1852 1853 </ItemizedList> 1854 1855 </Para> 1856 1857 <Sect2> 1858 <Title>cd</Title> 1859 1860 <Para> 1861 1862 <Screen> 1863 Syntax: cd [path] 1864 </Screen> 1865 1866 The <Command>cd</Command> command is used in the usual meaning, like the global cd 1867 command. 1868 1869 <ItemizedList> 1870 <ListItem> 1871 1872 <Para> 1873 If <Emphasis>path</Emphasis> is not specified, the current directory entry is 1874 followed. 1875 </Para> 1876 </ListItem> 1877 <ListItem> 1878 1879 <Para> 1880 <Emphasis>path</Emphasis> can be relative to the current directory. 1881 </Para> 1882 </ListItem> 1883 <ListItem> 1884 1885 <Para> 1886 <Emphasis>path</Emphasis> can also end up in a file, in which case the file inode 1887 will be reached. 1888 </Para> 1889 </ListItem> 1890 <ListItem> 1891 1892 <Para> 1893 Symbolic link (fast only, meanwhile) is automatically followed. 1894 </Para> 1895 </ListItem> 1896 1897 </ItemizedList> 1898 1899 </Para> 1900 1901 </Sect2> 1902 1903 <Sect2> 1904 <Title>entry</Title> 1905 1906 <Para> 1907 1908 <Screen> 1909 Syntax: entry [entry_num] 1910 </Screen> 1911 1912 The <Command>entry</Command> command sets <Emphasis>entry_num</Emphasis> as the current directory 1913 entry. 1914 </Para> 1915 1916 </Sect2> 1917 1918 <Sect2> 1919 <Title>followinode</Title> 1920 1921 <Para> 1922 1923 <Screen> 1924 Syntax: followinode 1925 </Screen> 1926 1927 The <Command>followinode</Command> command will move you to the inode pointed by the 1928 current directory entry. 1929 </Para> 1930 1931 </Sect2> 1932 1933 <Sect2> 1934 <Title>inode</Title> 1935 1936 <Para> 1937 1938 <Screen> 1939 Syntax: inode 1940 </Screen> 1941 1942 The <Command>inode</Command> command will return you to the parent inode of the whole 1943 directory listing. 1944 </Para> 1945 1946 </Sect2> 1947 1948 <Sect2> 1949 <Title>next</Title> 1950 1951 <Para> 1952 1953 <Screen> 1954 Syntax: next [num] 1955 </Screen> 1956 1957 The <Command>next</Command> command will pass to the next directory entry. 1958 If <Emphasis>num</Emphasis> is supplied, it will pass to the next <Emphasis>num</Emphasis> entries. 1959 </Para> 1960 1961 </Sect2> 1962 1963 <Sect2> 1964 <Title>prev</Title> 1965 1966 <Para> 1967 1968 <Screen> 1969 Syntax: prev [num] 1970 </Screen> 1971 1972 The <Command>prev</Command> command will pass to the previous directory entry. 1973 If <Emphasis>num</Emphasis> is supplied, it will pass to the previous <Emphasis>num</Emphasis> entries. 1974 </Para> 1975 1976 </Sect2> 1977 1978 <Sect2> 1979 <Title>writedata</Title> 1980 1981 <Para> 1982 1983 <Screen> 1984 Syntax: writedata 1985 </Screen> 1986 1987 The <Command>writedata</Command> command will write the current directory entry to the 1988 disk. 1989 </Para> 1990 1991 </Sect2> 1992 1993 </Sect1> 1994 1995 <Sect1 id="block-bitmap"> 1996 <Title>The block allocation bitmap</Title> 1997 1998 <Para> 1999 The <Literal remap="tt">block allocation bitmap</Literal> of any block group can be reached from 2000 the corresponding group descriptor. 2001 </Para> 2002 2003 <Para> 2004 You will be offered a bit listing of the entire blocks in the group. The 2005 current block will be highlighted and its number will be displayed in the 2006 status window. 2007 </Para> 2008 2009 <Para> 2010 A value of "1" means that the block is allocated, while a value of "0" 2011 signals that it is free. The value is also interpreted in the status 2012 window. You can use the usual <Command>next/prev</Command> commands, along with the 2013 <Command>allocate/deallocate</Command> commands. 2014 </Para> 2015 2016 <Sect2> 2017 <Title>allocate</Title> 2018 2019 <Para> 2020 2021 <Screen> 2022 Syntax: allocate [num] 2023 </Screen> 2024 2025 The <Command>allocate</Command> command allocates <Emphasis>num</Emphasis> blocks, starting from the 2026 highlighted position. If <Emphasis>num</Emphasis> is not specified, <Emphasis>num=1</Emphasis> is assumed. 2027 Of-course, no actual change is made until you issue a <Command>writedata</Command> command. 2028 </Para> 2029 2030 </Sect2> 2031 2032 <Sect2> 2033 <Title>deallocate</Title> 2034 2035 <Para> 2036 2037 <Screen> 2038 Syntax: deallocate [num] 2039 </Screen> 2040 2041 The <Command>deallocate</Command> command deallocates <Emphasis>num</Emphasis> blocks, starting from the 2042 highlighted position. If <Emphasis>num</Emphasis> is not specified, <Emphasis>num=1</Emphasis> is assumed. 2043 Of-course, no actual change is made until you issue a <Command>writedata</Command> command. 2044 </Para> 2045 2046 </Sect2> 2047 2048 <Sect2> 2049 <Title>entry</Title> 2050 2051 <Para> 2052 2053 <Screen> 2054 Syntax: entry [entry_num] 2055 </Screen> 2056 2057 The <Command>entry</Command> command sets the current highlighted block to 2058 <Emphasis>entry_num</Emphasis>. 2059 </Para> 2060 2061 </Sect2> 2062 2063 <Sect2> 2064 <Title>next</Title> 2065 2066 <Para> 2067 2068 <Screen> 2069 Syntax: next [num] 2070 </Screen> 2071 2072 The <Command>next</Command> command will pass to the next bit, which corresponds to the 2073 next block. If <Emphasis>num</Emphasis> is supplied, it will pass to the next <Emphasis>num</Emphasis> 2074 bits. 2075 </Para> 2076 2077 </Sect2> 2078 2079 <Sect2> 2080 <Title>prev</Title> 2081 2082 <Para> 2083 2084 <Screen> 2085 Syntax: prev [num] 2086 </Screen> 2087 2088 The <Command>prev</Command> command will pass to the previous bit, which corresponds to the 2089 previous block. If <Emphasis>num</Emphasis> is supplied, it will pass to the previous 2090 <Emphasis>num</Emphasis> bits. 2091 </Para> 2092 2093 </Sect2> 2094 2095 </Sect1> 2096 2097 <Sect1> 2098 <Title>The inode allocation bitmap</Title> 2099 2100 <Para> 2101 The <Literal remap="tt">inode allocation bitmap</Literal> is very similar to the block allocation 2102 bitmap explained above. It is also reached from the corresponding group 2103 descriptor. Please refer to section <XRef LinkEnd="block-bitmap">. 2104 </Para> 2105 2106 </Sect1> 2107 2108 <Sect1> 2109 <Title>Filesystem size limitation</Title> 2110 2111 <Para> 2112 While an ext2 filesystem has a size limit of <Literal remap="tt">4 TB</Literal>, EXT2ED currently 2113 <Literal remap="tt">can't</Literal> handle filesystems which are <Literal remap="tt">bigger than 2 GB</Literal>. 2114 </Para> 2115 2116 <Para> 2117 I am sorry for the inconvenience. This will hopefully be fixed in future 2118 releases. 2119 </Para> 2120 2121 </Sect1> 2122 2123 <Sect1> 2124 <Title>Copyright</Title> 2125 2126 <Para> 2127 EXT2ED is Copyright (C) 1995 Gadi Oxman. 2128 </Para> 2129 2130 <Para> 2131 EXT2ED is hereby placed under the GPL - Gnu Public License. You are free and 2132 welcome to copy, view and modify the sources. My only wish is that my 2133 copyright presented above will be left and that a list of the bug fixes, 2134 added features, etc, will be provided. 2135 </Para> 2136 2137 <Para> 2138 The entire EXT2ED project is based, of-course, on the kernel sources. The 2139 <Literal remap="tt">ext2.descriptors</Literal> distributed with EXT2ED is a slightly modified 2140 version of the main ext2 include file, /usr/include/linux/ext2_fs.h. Follows 2141 the original copyright: 2142 </Para> 2143 2144 <Para> 2145 2146 <Screen> 2147 /* 2148 * linux/include/linux/ext2_fs.h 2149 * 2150 * Copyright (C) 1992, 1993, 1994, 1995 2151 * Remy Card (card (a] masi.ibp.fr) 2152 * Laboratoire MASI - Institut Blaise Pascal 2153 * Universite Pierre et Marie Curie (Paris VI) 2154 * 2155 * from 2156 * 2157 * linux/include/linux/minix_fs.h 2158 * 2159 * Copyright (C) 1991, 1992 Linus Torvalds 2160 */ 2161 2162 </Screen> 2163 2164 </Para> 2165 2166 </Sect1> 2167 2168 <Sect1> 2169 <Title>Acknowledgments</Title> 2170 2171 <Para> 2172 EXT2ED was constructed as a student project in the software 2173 laboratory of the faculty of electrical-engineering in the 2174 <Literal remap="tt">Technion - Israel's institute of technology</Literal>. 2175 </Para> 2176 2177 <Para> 2178 At first, I would like to thank <PersonName><FirstName>Avner</FirstName> <SurName>Lottem</SurName></PersonName> and <PersonName><Honorific>Doctor</Honorific> <FirstName>Ilana</FirstName> <SurName>David</Surname></PersonName> for their interest and assistance in this project. 2179 </Para> 2180 2181 <Para> 2182 I would also like to thank the following people, who were involved in the 2183 design and implementation of the ext2 filesystem kernel code and support 2184 utilities: 2185 2186 <ItemizedList> 2187 <ListItem> 2188 2189 <Para> 2190 <PersonName><FirstName>Remy</FirstName> <SurName>Card</SurName></PersonName> 2191 2192 Who designed, implemented and maintains the ext2 filesystem kernel 2193 code, and some of the ext2 utilities. Remy Card is also the author 2194 of several helpful slides concerning the ext2 filesystem. 2195 Specifically, he is the author of <Literal remap="tt">File Management in the Linux 2196 Kernel</Literal> and of <Literal remap="tt">The Second Extended File System - Current State, 2197 Future Development</Literal>. 2198 2199 </Para> 2200 </ListItem> 2201 <ListItem> 2202 2203 <Para> 2204 <PersonName><FirstName>Wayne</FirstName> <SurName>Davison</SurName></PersonName> 2205 2206 Who designed the ext2 filesystem. 2207 </Para> 2208 </ListItem> 2209 <ListItem> 2210 2211 <Para> 2212 <PersonName><FirstName>Stephen</FirstName> <Surname>Tweedie</SurName></PersonName> 2213 2214 Who helped designing the ext2 filesystem kernel code and wrote the 2215 slides <Literal remap="tt">Optimizations in File Systems</Literal>. 2216 </Para> 2217 </ListItem> 2218 <ListItem> 2219 2220 <Para> 2221 <PersonName><FirstName>Theodore</FirstName> <SurName>Ts'o</SurName></PersonName> 2222 2223 Who is the author of several ext2 utilities and of the ext2 library 2224 <Literal remap="tt">libext2fs</Literal> (which I didn't use, simply because I didn't know 2225 it exists when I started to work on my project). 2226 </Para> 2227 </ListItem> 2228 2229 </ItemizedList> 2230 2231 </Para> 2232 2233 <Para> 2234 Lastly, I would like to thank, of-course, <PersonName><FirstName>Linus</FirstName> <SurName>Torvalds</SurName></PersonName> and the 2235 Linux community for providing all of us with such a great operating 2236 system. 2237 </Para> 2238 2239 <Para> 2240 Please contact me in a case of bug report, suggestions, or just about 2241 anything concerning EXT2ED. 2242 </Para> 2243 2244 <Para> 2245 Enjoy, 2246 </Para> 2247 2248 <Para> 2249 Gadi Oxman <tgud (a] tochnapc2.technion.ac.il> 2250 </Para> 2251 2252 <Para> 2253 Haifa, August 95 2254 </Para> 2255 2256 </Sect1> 2257 2258 </Article> 2259
