From 464df1d5e5ab1322e2dd0a7796939fff1aeefa9a Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 17:49:25 +0200 Subject: Adding upstream version 1.47.0. Signed-off-by: Daniel Baumann --- ext2ed/doc/user-guide.sgml | 2258 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 2258 insertions(+) create mode 100644 ext2ed/doc/user-guide.sgml (limited to 'ext2ed/doc/user-guide.sgml') diff --git a/ext2ed/doc/user-guide.sgml b/ext2ed/doc/user-guide.sgml new file mode 100644 index 0000000..1e8f3cd --- /dev/null +++ b/ext2ed/doc/user-guide.sgml @@ -0,0 +1,2258 @@ + + +
+ + + +EXT2ED - The Extended-2 filesystem editor - User's guide + +Gadi Oxman, tgud@tochnapc2.technion.ac.il + +v0.1, August 3 1995 + + + + +This is only the initial version of this document. It may be unclear at +some places. Please send me feedback with anything regarding to it. + + + + + + + +About EXT2ED documentation + + +The EXT2ED documentation consists of three parts: + + + + + + The ext2 filesystem overview. + + + + + + The EXT2ED user's guide. + + + + + + The EXT2ED design and implementation. + + + + + + + + +If you intend to used EXT2ED, I strongly suggest that you would be familiar +with the material presented in the ext2 filesystem overview as well. + + + +If you also intend to browse and modify the source code, I suggest that you +will also read the article The EXT2ED design and implementation, as it +provides a general overview of the structure of my source code. + + + + + +Introduction + + +EXT2ED is a "disk editor" for the ext2 filesystem. Its purpose is to show +you the internal structures of the ext2 filesystem in an rather intuitive +and logical way, so that it will be easier to "travel" between the various +internal filesystem structures. + + + + + +Basic concepts in EXT2ED + + +Two basic concepts in EXT2ED are commands and types. + + + +EXT2ED is object-oriented in the sense that it defines objects in the +filesystem, like a super-block or a directory. An object is +something which "knows" how to handle some aspect of the filesystem. + + + +Your interaction with EXT2ED is done through commands which EXT2ED +accepts. There are three levels of commands: + + + + + + General Commands + + + + + + Extended-2 Filesystem general commands + + + + + + Type specific commands + + + + + +The General commands are always available. + + + +The ext2 general commands are available only when editing an ext2 filesystem. + + + +The Type specific commands are available when editing a specific object in the +filesystem. Each object typically comes with its own set of internal +variables, and its own set of commands, which are fine tuned handle the +corresponding structure in the filesystem. + + + + + +Running EXT2ED + + +Running EXT2ED is as simple as typing ext2ed from the shell prompt. +There are no command line switches. + + + +When first run, EXT2ED parses its configuration file, ext2ed.conf. +This file must exist. + + + +When the configuration file processing is done, EXT2ED screen should appear +on the screen, with the command prompt ext2ed> displayed. + + + + + +EXT2ED user interface + + +EXT2ED uses the ncurses library for screen management. Your screen +will be divided into four parts, from top to bottom: + + + + + + Title window + + + + + + Status window + + + + + + Main editing window + + + + + + Command window + + + + + +The title window just displays the current version of EXT2ED. + + + +The status window will display various information regarding the state of +the editing at this point. + + + +The main editing window is the place at which the actual data will be shown. +Almost every command will cause some display at this window. This window, as +opposed to the three others, is of variable length - You always look at one +page of it. The current page and the total numbers of pages at this moment +is displayed at the status window. Moving between pages is done by the use +of the pgdn and pgup commands. + + + +The command window is at the bottom of the screen. It always displays a +command prompt ext2ed> and allows you to type a command. Feedback +about the commands entered is displayed to this window also. + + + +EXT2ED uses the readline library while processing a command line. All +the usual editing keys are available. Each entered command is placed into a +history of commands, and can be recalled later. Command Completion is also +supported - Just start to type a command, and press the completion key. + + + +Pressing enter at the command window, without entering a command, +recalls the last command. This is useful when moving between close entries, +in the next command, for example. + + + + + +Getting started + + +A few precautions + + +EXT2ED is a tool for filesystem editing. As such, it can be +dangerous. The summary to the subsections below is that +You must know what you are doing. + + + +A mounted filesystem + + +EXT2ED is not designed to work on a mounted filesystem - It is complicated +enough as it is; I didn't even try to think of handling the various race +conditions. As such, please respect the following advice: + + + +Do not use EXT2ED on a mounted filesystem ! + + + +EXT2ED will not allow write access to a mounted filesystem. Although it is +fairly easy to change EXT2ED so that it will be allowed, I hereby request +again- EXT2ED is not designed for that action, and will most likely corrupt +data if used that way. Please don't do that. + + + +Concerning read access, I chose to leave the decision for the user through +the configuration file option AllowMountedRead. Although read access +on a mounted partition will not do any damage to the filesystem, the data +displayed to you will not be reliable, and showing you incorrect information +may be as bad as corrupting the filesystem. However, you may still wish to +do that. + + + + + +Write access + + +Considering the obvious sensitivity of the subject, I took the following +actions: + + + + + + + + + EXT2ED will always start with a read-only access. Write access mode +needs to be specifically entered by the enablewrite command. +Until this is done, no write will be allowed. Write access can be +disabled at any time with disablewrite. When +enablewrite is issued, the device is reopened in read-write +mode. Needless to say, the device permissions should allow that. + + + + + + As a second level of protection, you can disallow write access in +the configuration file by using the AllowChanges off +configuration option. In this case, the enablewrite command +will be refused. + + + + + + When write access is enabled, the data will never change +immediately. Rather, a specific writedata command is needed +to update the object in the disk with the changed object in memory. + + + + + + In addition, A logging option is provided through the configuration +file options LogChanges and LogFile. With logging +enabled, each change to the disk will be logged at a very primitive +level - A hex dump of the original data and of the new written data. +The log file will be a text file which is easily readable, and you +can make use of it to undo any changes which you made (EXT2ED doesn't +make use of the log file for that purpose, it just logs the changes). + + + + + +Please remember that this is only the initial release of EXT2ED, and it is +not very much tested - It is reasonable to assume that there are +bugs. +However, the logging option above can offer protection even from this +unfortunate case. Therefor, I highly recommend that at least when first +working with EXT2ED, the logging option will be enabled, despite the disk +space which it consumes. + + + + + + + +The help command + + +When loaded, EXT2ED will show a short help screen. This help screen can +always be retrieved by the command help. The help screen displays a +list of all the commands which are available at this point. At startup, only +the General commands are available. +This will change with time, since each object has its own commands. Thus, +commands which are available now may not be available later. +Using help command will display additional information about +the specific command command. + + + + + +The setdevice command + + +The first command that is usually entered to EXT2ED is the setdevice +command. This command simply tells EXT2ED on which device the filesystem is +present. For example, suppose my ext2 filesystem is on the first partition +of my ide disk. The command will be: + + +setdevice /dev/hda1 + + +The following actions will take place in the following order: + + + + + + EXT2ED will check if the partition is mounted. +If the partition is mounted (highly not recommended), +the accept/reject behavior will be decided by the configuration +file. Cross reference section . + + + + + + The specified device will be opened in read-only mode. The +permissions of the device should be set in a way that allows +you to open the device for read access. + + + + + + Autodetection of an ext2 filesystem will be made by searching for +the ext2 magic number in the main superblock. + + + + + + In the case of a successful recognition of an ext2 filesystem, the +ext2 filesystem specific commands and the ext2 specific object +definitions will be registered. The object definitions will be read +at run time from a file specified by the configuration file. + +In case of a corrupted ext2 filesystem, it is quite possible that +the main superblock is damaged and autodetection will fail. In that +case, use the configuration option ForceExt2 on. This is not +the default case since EXT2ED can be used at a lower level to edit a +non-ext2 filesystem. + + + + + + In a case of a successful autodetection, essential information about +the filesystem such as the block size will be read from the +superblock, unless the used overrides this behavior with an +configuration option (not recommended). In that case, the parameters +will be read from the configuration file. + +In a case of an autodetection failure, the essential parameters +will be read from the configuration file. + + + + + +Assuming that you are editing an ext2 filesystem and that everything goes +well, you will notice that additional commands are now available in the help +screen, under the section ext2 filesystem general commands. In +addition, EXT2ED now recognizes a few objects which are essential to the +editing of an ext2 filesystem. + + + + + + + +Two levels of usage + + +Low level usage + + +This section explains what EXT2ED provides even when not editing an ext2 +filesystem. + + + +Even at this level, EXT2ED is more than just a hex editor. It still allows +definition of objects and variables in run time through a user file, +although of-course the objects will not have special fine tuned functions +connected to them. EXT2ED will allow you to move in the filesystem using +setoffset, and to apply an object definition on a specific place +using settype type. From this point and on, the object will +be shown in its native form - You will see a list of the +variables rather than just a hex dump, and you will be able to change each +variable in the intuitive form set variable=value. + + + +To define objects, use the configuration option AlternateDescriptors. + + + +There are now two forms of editing: + + + + + + Editing without a type. In this case, the disk block will be shown +as a text+hex dump, and you will be able to move along and change it. + + + + + + Editing with a type. In this case, the object's variables will be +shown, and you will be able to change each variable in its native form. + + + + + + + + + + +High level usage + + +EXT2ED was designed for the editing of the ext2 filesystem. As such, it +"understands" the filesystem structure to some extent. Each object now has +special fine tuned 'C' functions connected to it, which knows how to display +it in an intuitive form, and how the object fits in the general design of +the ext2 filesystem. It is of-course much easier to use this type of +editing. For example: + + +Issue group 2 to look at the main copy of the third group block +descriptor. With gocopy 1 you can move to its first backup copy, +and with inode you can start editing the inode table of the above +group block. From here, if the inode corresponds to a file, you can +use file to edit the file in a "continuous" way, using +nextblock to pass to its next block, letting EXT2ED following by +itself the direct blocks, indirect blocks, ..., while still preserving the +actual view of the exact block usage of the file. + + +The point is that the "tour" of the filesystem will now be synchronous rather +than asynchronous - Each object has the "links" to pass between connected +logical structures, and special fine-tuned functions to deal with it. + + + + + + + +General commands + + +I will now start with a systematic explanation of the general commands. +Please feel free to experiment, but take care when using the +enablewrite command. + + + +Whenever a command syntax is specified, arguments which are optional are +enclosed with square brackets. + + + +Please note that in EXT2ED, each command can be overridden by a specific +object to provide special fine-tuned functionality. In general, I was +attempting to preserve the similarity between those functions, which are +accessible by the same name. + + + +disablewrite + + + + +Syntax: disablewrite + + +disablewrite is used to reopen the device with read-only access. When +first running EXT2ED, the device is opened in read-only mode, and an +explicit enablewrite is required for write access. When finishing +with changing, a disablewrite is recommended for safety. Cross +reference section . + + + + + +enablewrite + + + + +Syntax: enablewrite + + +enablewrite is used to reopen the device with read-write access. +When first running EXT2ED, the device is opened in read-only mode, and an +explicit enablewrite is required for write access. +enablewrite will fail if write access is disabled from the +configuration file by the AllowChanges off configuration option. +Even after enablewrite, an explicit writedata +is required to actually write the new data to the disk. +When finishing with changing, a disablewrite is recommended for safety. +Cross reference section . + + + + + +help + + + + +Syntax: help [command] + + +The help command is described at section . + + + + + +next + + + + +Syntax: next [number] + + +This section describes the general command next. next +is overridden by several types in EXT2ED, to provide fine-tuned +functionality. + + + +The next general command behavior is depended on whether you are editing a +specific object, or none. + + + + + + + + + In the case where Type is none (The current type is showed +on the status window by the show command), next +passes to the next number bytes in the current edited block. +If number is not specified, number=1 is assumed. + + + + + + In the case where Type is defined, the next commands assumes +that you are editing an array of objects of that type, and the +next command will just pass to the next entry in the array. +If number is defined, it will pass number entries +ahead. + + + + + + + + + + +pgdn + + + + +Syntax: pgdn + + +Usually the edited data doesn't fit into the visible main window. In this +case, the status window will indicate that there is more to see "below" by +the message Page x of y. This means that there are y pages +total, and you are currently viewing the x page. With the pgdn +command, you can pass to the next available page. + + + + + +pgup + + + + +Syntax: pgup + + + + + +pgup is the opposite of pgdn - It will pass to the previous +page. Cross reference section . + + + + + +prev + + + + +Syntax: prev [number] + + + + + +prev is the opposite of next. Cross reference section +. + + + + + +recall + + + + +Syntax: recall object + + +recall is the opposite of remember. It will place you at the +place you where when saving the object position and type information. Cross +reference section . + + + + + +redraw + + + + +Syntax: redraw + + +Sometimes the screen display gets corrupted. I still have problems with +this. The redraw command simply redraws the entire display screen. + + + + + +remember + + + + +Syntax: remember object + + +EXT2ED provides you memory of objects; While editing, you may reach an +object which you will like to return to later. The remember command +will store in memory the current place and type of the object. You can +return to the object by using the recall command. Cross reference +section . + + + +Note: + + + + + + When remembering a file or a directory, the +corresponding inode will be saved in memory. The basic reason is that +the inode is essential for finding the blocks of the file or the +directory. + + + + + + + + + + +set + + + + +Syntax: set [text || hex] arg1 [arg2 arg3 ...] + +or + +Syntax: set variable=value + + +The set command is used to modify the current data. +The set general command behavior is depended on whether you are editing a +specific object, or none. + + + + + + + + + In the case where Type is none, the first syntax should be +used. The set command affects the data starting at the current +highlighted position in the edited block. + + + + + + When using the set hex command, a list of +hexadecimal bytes should follow. + + + + + + When using the set text command, it should be followed +by a text string. + + + + + +Examples: + + + set hex 09 0a 0b 0c 0d 0e 0f + set text Linux is just great ! + + + + + + + + + In the case where Type is defined, the second syntax should be used. +The set commands just sets the variable variable with the +value value. + + + + + +In any case, the data is only changed in memory. For an actual update to the +disk, use the writedata command. + + + + + +setdevice + + + + +Syntax: setdevice device + + +The setdevice command is described at section . + + + + + +setoffset + + + + +Syntax: setoffset [block || type] [+|-]offset + + +The setoffset command is used to move asynchronously inside the file +system. It is considered a low level command, and usually should not be used +when editing an ext2 filesystem, simply because movement is better +utilized through the specific ext2 commands. + + + +The offset is in bytes, and meanwhile should be positive and smaller +than 2GB. + + + +Use of the block modifier changes the counting unit to block. + + + +Use of the + or - modifiers signals that the offset is relative to +the current position. + + + +use of the type modifier is allowed only with relative offset. This +modifier will multiply the offset by the size of the current type. + + + + + +settype + + + + +Syntax: settype type || [none | hex] + + +The settype command is used to move apply the object definitions of +the type type on the current position. It is considered a low level +command and usually should not be used when editing an ext2 filesystem since +EXT2ED provides better tools. It is of-course very useful when editing a +non-ext2 filesystem and using user-defined objects. + + + +When type is hex or none, the data will be displayed as +a hex and text dump. + + + + + +show + + + + +Syntax: show + + +The show command will show the data of the current object at the +current position on the main display window. It will also update the status +window with type specific information. It may be necessary to use +pgdn and pgup to view the entire data. + + + + + +writedata + + + + +Syntax: writedata + + +The writedata command will update the disk with the object data that +is currently in memory. This is the point at which actual change is made to +the filesystem. Without this command, the edited data will not have any +effect. Write access should be allowed for a successful update. + + + + + + + +Editing an ext2 filesystem + + +In order to edit an ext2 filesystem, you should, of course, know the structure +of the ext2 filesystem. If you feel that you lack some knowledge in this +area, I suggest that you do some of the following: + + + + + + Read the supplied ext2 technical information. I tried to summarize +the basic information which is needed to get you started. + + + + + + Get the slides that Remy Card (The author of the ext2 filesystem) +prepared concerning the ext2 filesystem. + + + + + + Read the kernel sources. + + + + + +At this point, you should be familiar with the following terms: +block, inode, superblock, block groups, block allocation bitmap, inode +allocation bitmap, group descriptors, file, directory.Most of the above +are objects in EXT2ED. + + + +When editing an ext2 filesystem it is recommended that you use the ext2 +specific commands, rather then the general commands setoffset and +settype, mainly because: + + + + + + In most cases it will be unreliable, and will display incorrect +information. + +Sometimes in order to edit an object, EXT2ED needs the information +of some other related objects. For example, when editing a +directory, EXT2ED needs access to the inode of the edited directory. +Simply setting the type to a directory will be unreliable, +since the object assumes that you passed through its inode to reach +it, and expects this information, which isn't initialized if you +directly set the type to a directory. + + + + + + EXT2ED offers far better tools for handling the ext2 filesystem +using the ext2 specific commands. + + + + + + + + + + +ext2 general commands + + +The ext2 general commands are available only when you are editing an +ext2 filesystem. They are general in the sense that they are not +specific to some object, and can be invoked anytime. + + + +super + + + + +Syntax: super + + +The super command will "bring you" to the main superblock copy. It +will automatically set the object type to ext2_super_block. Then you +will be able to view and edit the superblock. When you are in the +superblock, other commands will be available. + + + + + +group + + + + +Syntax: group [number] + + +The group command will "bring you" to the main copy of the +number group descriptor. It will automatically set the object type to +ext2_group_desc. Then you will be able to view and edit the group +descriptor entry. When you are there, other commands will be available. + + + + + +cd + + + + +Syntax: cd path + + +The cd command will let you travel in the filesystem in the nice way +that the mounted filesystem would have let you. + + + +The cd command is a complicated command. Although it may sound +simple at first, an implementation of a typical cd requires passing through +the group descriptors, inodes, directory entries, etc. For example: + + + +The innocent cd /usr command can be done by using more primitive +EXT2ED commands in the following way (It is implemented exactly this way): + + + + + + Using group 0 to go to the first group descriptor. + + + + + + Using inode to get to the Bad blocks inode. + + + + + + Using next to pass to the root directory inode. + + + + + + Using dir to see the directory. + + + + + + Using next until we find the directory usr. + + + + + + Using followinode to pass to the inode corresponding to usr. + + + + + + Using dir to see the directory of /usr. + + + + + +And those commands aren't that primitive; For example, the tracing of the +blocks which belong to the root directory is done automatically by the dir +command behind the scenes, and the followinode command will automatically +"run" to the correct group descriptor in order to find the required inode. + + + +The path to the general cd command needs to be a full pathname - +Starting from /. The cd command stops at the last reachable +point, which can be a directory entry, in which case the type will be set to +dir, or an inode, in which case the type will be set to +ext2_inode. Symbolic links (Only fast symbolic links, meanwhile) are +automatically followed (if they are not across filesystems, of-course). If +the type is set to dir, you can use a path relative to the +"current directory". + + + + + + + +The superblock + + +The superblock can always be reached by the ext2 general command +super. Cross reference section . + + + +The status window will show you which copy of the superblock copies you are +currently editing. + + + +The main data window will show you the values of the various superblock +variables, along with some interpretation of the values. + + + +Data can be changed with the set and writedata commands. + + +For example, set s_r_blocks_count=1400 will reserve 1400 blocks for root. + + + + + +gocopy + + + + +Syntax: gocopy number + + +The gocopy command will "bring you" to the backup copy number +of the superblock copies. gocopy 0, for example, will bring you to +the main copy. + + + + + +setactivecopy + + + + +Syntax: setactivecopy + + +The setactivecopy command will copy the contents of the current +superblock copy onto the contents of the main copy. It will also switch to +editing of the main copy. No actual data is written to disk, of-course, +until you issue the writedata command. + + + + + + + +The group descriptors + + +The group descriptors can be edited by the group command. + + + +The status window will indicate the current group descriptor, the total +number of group descriptors (and hence of group blocks), and the backup copy +number. + + + +The main data window will just show you the values of the various variables. + + + +Basically, you can use the next and prev commands, along with the +set command, to modify the group descriptors. + + + +The group descriptors object is a junction, from which you can reach: + + + + + + The inode table of the corresponding block group (the inode +command) + + + + + + The block allocation bitmap (the blockbitmap command) + + + + + + The inode allocation bitmap (the inodebitmap command) + + + + + + + + +blockbitmap + + + + +Syntax: blockbitmap + + +The blockbitmap command will let you edit the block bitmap allocation +block of the current group block. + + + + + +entry + + + + +Syntax: entry number + + +The entry command will move you to the number group descriptor in the +group descriptors table. + + + + + +inode + + + + +Syntax: inode + + +The inode command will pass you to the first inode in the current +group block. + + + + + +inodebitmap + + + + +Syntax: inodebitmap + + +The inodebitmap command will let you edit the inode bitmap allocation +block of the current group block. + + + + + +next + + + + +Syntax: next [number] + + +The next command will pass to the next number group +descriptor. If number is omitted, number=1 is assumed. + + + + + +prev + + + + +Syntax: prev [number] + + +The prev command will pass to the previous number group +descriptor. If number is omitted, number=1 is assumed. + + + + + +setactivecopy + + + + +Syntax: setactivecopy + + +The setactivecopy command copies the contents of the current group +descriptor, to its main copy. The updated main copy will then be shown. No +actual change is made to the disk until you issue the writedata +command. + + + + + + + +The inode + + +An inode can be reached by the following two ways: + + + + + + Using inode from the corresponding group descriptor. + + + + + + Using followinode from a directory entry. + + + + + + Using the cd command with the pathname to the file. + +For example, cd /usr/src/ext2ed/ext2ed.h + + + + + + + + +The status window will indicate: + + + + + + The current global inode number. + + + + + + The total total number of inodes. + + + + + + On which block group the inode is allocated. + + + + + + The total number of inodes in this group block. + + + + + + The index of the current inode in the current group block. + + + + + + The type of the inode (file, directory, special, etc). + + + + + + + + +The main data window, in addition to the list of variables, will contain +some interpretations on the right side. + + + +If the inode corresponds to a file, you can use the file command to +edit the file. + + + +If the inode is an inode of a directory, you can use the dir command +to edit the directory. + + + +dir + + + + +Syntax: dir + + +If the inode mode corresponds to a directory (shown on the status window), +you can enter directory mode editing by using dir. + + + + + +entry + + + + +Syntax: entry number + + +The entry command will move you to the number inode in the +current inode table. + + + + + +file + + + + +Syntax: file + + +If the inode mode corresponds to a file (shown on the status window), +you can enter file mode editing by using file. + + + + + +group + + + + +Syntax: group + + +The group command is used to go to the group descriptor of the +current group block. + + + + + +next + + + + +Syntax: next [number] + + +The next command will pass to the next number inode. +If number is omitted, number=1 is assumed. + + + + + +prev + + + + +Syntax: prev [number] + + +The prev command will pass to the previous number inode. +If number is omitted, number=1 is assumed. + + + + + + + +The file + + +When editing a file, EXT2ED offers you a both a continuous and a true +fragmented view of the file - The file is still shown block by block with +the true block number at each stage and EXT2ED offers you commands which +allow you to move between the file blocks, while finding the +allocated blocks by using the inode information behind the scenes. + + + +Aside from this, the editing is just a hex editing - You move the +cursor in the current block of the file by using next and +prev, move between blocks by nextblock and prevblock, +and make changes by the set command. Note that the set command is +overridden here - There are no variables. The writedata command will +update the current block to the disk. + + + +Reaching a file can be done by using the file command from its inode. +The inode can be reached by any other means, for example, by the +cd command, if you know the file name. + + + +The status window will indicate: + + + + + + The global block number. + + + + + + The internal file block number. + + + + + + The file offset. + + + + + + The file size. + + + + + + The file inode number. + + + + + + The indirection level - Whether it is a direct block (0), indirect +(1), etc. + + + + + + + + +The main data window will display the file either in hex mode or in text +mode, select-able by the display command. + + + +In hex mode, EXT2ED will display offsets in the current block, along with a +text and hex dump of the current block. + + + +In either case the current place will be highlighted. In the hex mode +it will be always highlighted, while in the text mode it will be highlighted +if the character is display-able. + + + +block + + + + +Syntax: block block_num + + +The block command is used to move inside the file. The +block_num argument is the requested internal file block number. A +value of 0 will reach the beginning of the file. + + + + + +display + + + + +Syntax: display [text || hex] + + +The display command changes the display mode of the file. +display +hex will switch to hex mode, while display text will switch +to text mode. The default mode when no display command is issued is +hex mode. + + + + + +inode + + + + +Syntax: inode + + +The inode command will return to the inode of the current file. + + + + + +next + + + + +Syntax: next [num] + + +The next command will pass to the next byte in the file. If +num is supplied, it will pass to the next num bytes. + + + + + +nextblock + + + + +Syntax: nextblock [num] + + +The nextblock command will pass to the next block in the file. If +num is supplied, it will pass to the next num blocks. + + + + + +prev + + + + +Syntax: prev [num] + + +The prev command will pass to the previous byte in the file. If +num is supplied, it will pass to the previous num bytes. + + + + + +prevblock + + + + +Syntax: prevblock [num] + + +The nextblock command will pass to the previous block in the file. If +num is supplied, it will pass to the previous num blocks. + + + + + +offset + + + + +Syntax: offset file_offset + + +The offset command will move to the specified offset in the file. + + + + + +set + + + + +Syntax: set [text || hex] arg1 [arg2 arg3 ...] + + +The file set command is working like the general set command, +with type=none. There are no variables. + + + + + +writedata + + + + +Syntax: writedata + + +The writedata command will update the current file block in the disk. + + + + + + + +The directory + + +When editing a file, EXT2ED analyzes for you both the allocation blocks of +the directory entries, and the directory entries. + + + +Each directory entry is displayed on one row. You can move the highlighted +entry with the usual next and prev commands, and "dive in" +with the followinode command. + + + +The status window will indicate: + + + + + + The directory entry number. + + + + + + The total number of directory entries in this directory. + + + + + + The current global block number. + + + + + + The current offset in the entire directory - When viewing the +directory as a continuous file. + + + + + + The inode number of the directory itself. + + + + + + The indirection level - Whether it is a direct block (0), indirect +(1), etc. + + + + + + + + +cd + + + + +Syntax: cd [path] + + +The cd command is used in the usual meaning, like the global cd +command. + + + + + + If path is not specified, the current directory entry is +followed. + + + + + + path can be relative to the current directory. + + + + + + path can also end up in a file, in which case the file inode +will be reached. + + + + + + Symbolic link (fast only, meanwhile) is automatically followed. + + + + + + + + + + +entry + + + + +Syntax: entry [entry_num] + + +The entry command sets entry_num as the current directory +entry. + + + + + +followinode + + + + +Syntax: followinode + + +The followinode command will move you to the inode pointed by the +current directory entry. + + + + + +inode + + + + +Syntax: inode + + +The inode command will return you to the parent inode of the whole +directory listing. + + + + + +next + + + + +Syntax: next [num] + + +The next command will pass to the next directory entry. +If num is supplied, it will pass to the next num entries. + + + + + +prev + + + + +Syntax: prev [num] + + +The prev command will pass to the previous directory entry. +If num is supplied, it will pass to the previous num entries. + + + + + +writedata + + + + +Syntax: writedata + + +The writedata command will write the current directory entry to the +disk. + + + + + + + +The block allocation bitmap + + +The block allocation bitmap of any block group can be reached from +the corresponding group descriptor. + + + +You will be offered a bit listing of the entire blocks in the group. The +current block will be highlighted and its number will be displayed in the +status window. + + + +A value of "1" means that the block is allocated, while a value of "0" +signals that it is free. The value is also interpreted in the status +window. You can use the usual next/prev commands, along with the +allocate/deallocate commands. + + + +allocate + + + + +Syntax: allocate [num] + + +The allocate command allocates num blocks, starting from the +highlighted position. If num is not specified, num=1 is assumed. +Of-course, no actual change is made until you issue a writedata command. + + + + + +deallocate + + + + +Syntax: deallocate [num] + + +The deallocate command deallocates num blocks, starting from the +highlighted position. If num is not specified, num=1 is assumed. +Of-course, no actual change is made until you issue a writedata command. + + + + + +entry + + + + +Syntax: entry [entry_num] + + +The entry command sets the current highlighted block to +entry_num. + + + + + +next + + + + +Syntax: next [num] + + +The next command will pass to the next bit, which corresponds to the +next block. If num is supplied, it will pass to the next num +bits. + + + + + +prev + + + + +Syntax: prev [num] + + +The prev command will pass to the previous bit, which corresponds to the +previous block. If num is supplied, it will pass to the previous +num bits. + + + + + + + +The inode allocation bitmap + + +The inode allocation bitmap is very similar to the block allocation +bitmap explained above. It is also reached from the corresponding group +descriptor. Please refer to section . + + + + + +Filesystem size limitation + + +While an ext2 filesystem has a size limit of 4 TB, EXT2ED currently +can't handle filesystems which are bigger than 2 GB. + + + +I am sorry for the inconvenience. This will hopefully be fixed in future +releases. + + + + + +Copyright + + +EXT2ED is Copyright (C) 1995 Gadi Oxman. + + + +EXT2ED is hereby placed under the GPL - Gnu Public License. You are free and +welcome to copy, view and modify the sources. My only wish is that my +copyright presented above will be left and that a list of the bug fixes, +added features, etc, will be provided. + + + +The entire EXT2ED project is based, of-course, on the kernel sources. The +ext2.descriptors distributed with EXT2ED is a slightly modified +version of the main ext2 include file, /usr/include/linux/ext2_fs.h. Follows +the original copyright: + + + + + +/* + * linux/include/linux/ext2_fs.h + * + * Copyright (C) 1992, 1993, 1994, 1995 + * Remy Card (card@masi.ibp.fr) + * Laboratoire MASI - Institut Blaise Pascal + * Universite Pierre et Marie Curie (Paris VI) + * + * from + * + * linux/include/linux/minix_fs.h + * + * Copyright (C) 1991, 1992 Linus Torvalds + */ + + + + + + + + +Acknowledgments + + +EXT2ED was constructed as a student project in the software +laboratory of the faculty of electrical-engineering in the +Technion - Israel's institute of technology. + + + +At first, I would like to thank Avner Lottem and Doctor Ilana David for their interest and assistance in this project. + + + +I would also like to thank the following people, who were involved in the +design and implementation of the ext2 filesystem kernel code and support +utilities: + + + + + +Remy Card + +Who designed, implemented and maintains the ext2 filesystem kernel +code, and some of the ext2 utilities. Remy Card is also the author +of several helpful slides concerning the ext2 filesystem. +Specifically, he is the author of File Management in the Linux +Kernel and of The Second Extended File System - Current State, +Future Development. + + + + + + +Wayne Davison + +Who designed the ext2 filesystem. + + + + + +Stephen Tweedie + +Who helped designing the ext2 filesystem kernel code and wrote the +slides Optimizations in File Systems. + + + + + +Theodore Ts'o + +Who is the author of several ext2 utilities and of the ext2 library +libext2fs (which I didn't use, simply because I didn't know +it exists when I started to work on my project). + + + + + + + + +Lastly, I would like to thank, of-course, Linus Torvalds and the +Linux community for providing all of us with such a great operating +system. + + + +Please contact me in a case of bug report, suggestions, or just about +anything concerning EXT2ED. + + + +Enjoy, + + + +Gadi Oxman <tgud@tochnapc2.technion.ac.il> + + + +Haifa, August 95 + + + + +
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