fsdb(1M) fsdb(1M)NAME fsdb - debugs the file system SYNOPSIS fsdb [-?] [-o] [-pstring] [-T4.2] [-w] UFS-symbol... fsdb [-] [-T5.2] SVFS-symbol... ARGUMENTS - Disables error-checking routines to verify inode and block addresses. This option can only be used with an SVFS file system. -? Displays the usage. This option can only be used with the UFS file system. -o Overrides some error conditions. This option can only be used with the UFS file system. -pstring Specifies a new prompt. Replace string with the new prompt. This option can only be used with the UFS file system. SVFS-symbol Specifies the symbol recognized by fsdb for an SVFS file system. The SVFS symbols are: # Indicates an absolute address. i Converts from an inumber to an inode address. b Converts to a block address. d Indicates directory slot offset. +,- Addresses arithmetic. q Quits. >,< Saves and restores an address. = Indicates numerical assignment. =+ Increments assignment. =- Decrements assignment. =" " " " " " Indicates character-string assignment. O Indicates error-checking flip-flop. January 1992 1
fsdb(1M) fsdb(1M)p Indicates general print facilities. f Indicates file print facility. B Indicates byte mode. W Indicates word mode. D Indicates double-word mode. ! Escapes to the shell. -T4.2 Indicates that you are debugging a Berkeley 4.2 file system (UFS). -T5.2 Indicates that you are debugging a System V file system (SVFS). UFS-symbol Specifies the symbol recognized by fsdb for the UFS file system. The UFS symbols are: RETURN Updates the value of dot by the current value of type and display using the current value of count. # Indicates numeric expressions that may be composed of +, -, *, and % operators (evaluated left to right) and may use parentheses. Once evaluated, the value of dot is updated. , count Indicates count. The global value of count is updated to count. The value of count remains until a new command is run. A count specifier of * attempts to show a block of information. The default for count is 1. ? f Displays in structured style with format specifier f (see the section ``Formatted Output''). / f Displays in unstructured style with format specifier f (see the section ``Formatted Output''). . Indicates the value of dot. 2 January 1992
fsdb(1M) fsdb(1M)+e Increment the value of dot by the expression e. The amount actually incremented is dependent on the size of type: dot = dot + e * sizeof (type) The default for e is 1. -e Decrements the value of dot by the expression e (see +). *e Multiplies the value of dot by the expression e. Multiplication and division don't use type. In the above calculation of dot, consider the size of (type) to be 1. %e Divides the value of dot by the expression e (see *). < name Restores an address saved in register name, which must be a single letter or digit. > name Saves an address in register name, which must be a single letter or digit. = f Displays indicator. If f is a legitimate format specifier (see the section ``Formatted Output''), then the value of dot is displayed using format specifier f. Otherwise, assignment is assumed (see the next item). = [s] [e] Indicates assignment. The address pointed to by dot has its contents changed to the value of the expression e or to the ASCII representation of the quoted (") string s. This may be useful for changing directory names or ASCII file information. =+ e Increments assignment. The address pointed to by dot has its contents incremented by expression e. =- e Decrements assignment. The address pointed to by dot has its contents decremented by expression e. -w Enables you to modify any portion of the disk for the UFS file system. The disk is open for writing. January 1992 3
fsdb(1M) fsdb(1M)DESCRIPTION fsdb can be used to patch up a damaged file system after a crash. It has conversions to translate block and inumbers into their corresponding disk addresses. Also included are mnemonic offsets to access different parts of an inode. These greatly simplify the process of correcting control- block entries or descending the file-system tree. Since fsdb reads the disk raw, it is able to circumvent normal file-system security. Extreme caution is advised in determining its availability on the system. Suggested permissions are 600 and owned by bin. The fsdb command contains several error-checking routines to verify inode and block addresses. These routines can be disabled, if necessary, by invoking fsdb with the -o option for the UFS file system or by using the - option for an SVFS file system. The fsdb command reads a block at a time and therefore works with raw as well as block I/O. A buffer management routine is used to retain commonly used blocks of data in order to reduce the number of read system calls. All assignment operations result in an immediate write-through of the corresponding block. Wherever possible, syntax similar to adb syntax was adopted to promote the use of fsdb through familiarity. The fsdb command considers numbers in UFS as hexadecimal by default and considers numbers in SVFS as decimal by default. However, the user has control over how data is to be displayed or accepted. The base command displays or sets the input/output base. Once set, all input defaults to this base, and all output is shown in this base. The base can be overridden temporarily for input by preceding hexadecimal numbers with 0x, preceding decimal numbers with 0t, or preceding octal numbers with 0. Hexadecimal numbers beginning with a-f or A-F must be preceded with 0x to distinguish them from commands. Disk addressing by fsdb is at the byte level. However, fsdb offers many commands to convert a desired inode, directory entry, block, superblock, and so on, to a byte address. Once the address is calculated, fsdb records the result in the current address, or dot. Several global values are maintained by fsdb: the current base (referred to as base), the current address (referred to as dot), the current inode (referred to as inode), the current count (referred to as count), and the current type (referred to as type). Most commands use the preset value 4 January 1992
fsdb(1M) fsdb(1M)of dot in their execution. For example, > 2:inode first sets the value of dot to 2, The : (colon) alerts the start of a command, and the inode command sets inode to 2. A count is specified after a , (comma). Once set, count remains at this value until a new command is encountered, which then resets the value back to 1 (the default). So, if > 2000,400/X is typed, 400 hex longs are listed from 2000, and when completed, the value of dot is 2000 + 400 * size of (long). If a RETURN is then typed, the output routine uses the current values of dot, count, and type and displays 400 more hex longs. A * causes the entire block to be displayed. End of fragment, block, and file are maintained by fsdb. When displaying data as fragments or blocks, an error message is displayed when the end of fragment or block is reached. When displaying data using the db, ib, directory, or file commands, an error message is displayed if the end- of-file is reached. This is mainly needed to avoid passing the end of a directory or file and getting unknown and unwanted results. Two examples showing several commands and the use of RETURN are: > 2:ino; 0:dir?d > 2:ino; 0:db:block?d These two examples are synonymous for getting to the first directory entry of the root of the file system. Once there, subsequent use of RETURN (or +, -) will advance to subsequent entries. Note that these two examples: > 2:inode; :ls > :ls / are also synonymous. The print facilities generate a formatted output in various styles. The current address is normalized to an appropriate boundary before printing begins. It advances with the printing and is left at the address of the last item printed. The output can be terminated at any time by typing the interrupt character. If a number follows the p symbol, that many entries are printed. A check is made to detect January 1992 5
fsdb(1M) fsdb(1M)block boundary overflows because logically sequential blocks are generally not physically sequential. If a count of 0 is used, all entries to the end of the current block are printed. The print options available are: i Print as inodes. d Print as directories. o Print as octal words. e Print as decimal words. c Print as characters. b Print as octal bytes. The f symbol is used to print data blocks associated with the current inode. If followed by a number, that block of the file is printed. (Blocks are numbered from 0.) The desired print option letter follows the block number, if present, or the f symbol. This print facility works for small as well as large files. It checks for special devices and checks that the block pointers used to find the data are not 0. Dots, tabs, and spaces may be used as function delimiters but are not necessary. A line with just a newline character increments the current address by the size of the data type last printed; that is, the address is set to the next byte, word, double word, directory entry, or inode, allowing the user to step through a region of a file system. Information is printed in a format appropriate to the data type. Bytes, words, and double words are displayed with the octal address followed by the value in octal and decimal. A .B or .D is appended to the address for byte and double-word values, respectively. Directories are printed as a directory slot offset followed by the decimal inumber and the character representation of the entry name. Inodes are printed with labeled fields describing each element. UFS COMMANDS A command must be prefixed by a : (colon) character. Only enough letters of the command to uniquely distinguish it are needed. Multiple commands may be entered on one line by separating them by a space, tab, or ; (semicolon). In order to view a potentially unmounted disk in a reasonable manner, fsdb offers the cd, pwd, ls, and find commands. The functionality of these commands substantially matches that of their UNIX(Reg.) counterparts (see individual commands for details). The asterisk (*), question mark (?), and hyphen [-] wildcard characters are available. base=b Displays or sets base. As stated above, all input and 6 January 1992
fsdb(1M) fsdb(1M)output is governed by the current base. If the =b is left off, the current base is displayed. Otherwise, the current base is set to b. Note that b is interpreted using the old value of base, so to ensure correctness, use the 0, 0t, or 0x prefix when changing base. The default for base is hexadecimal. block Converts the value of dot to a block address. cd dir Changes the current directory to directory dir. The current values of inode and dot are also updated. If no dir is specified, then change directories to inode 2 ("/"). cg Converts the value of dot to a cylinder group. directory Converts the value of dot to a directory slot offset in that directory so that dot now points to this entry, if the current inode is a directory. file Takes the value of dot as a relative block count from the beginning of the file. The value of dot is updated to the first byte of this block. find dir [-name n] [-inum i] Finds files by name or inumber. find recursively searches directory dir and below for filenames whose inumber matches i or whose name matches pattern n. Note that only one of the two options: (C-name or -inum) may be used at one time. Also, -print is not needed or accepted. fill=p Fills an area of disk with pattern p. The area of disk is delimited by dot and count. fragment Converts the value of dot to a fragment address. The only difference between the fragment command and the block command is the amount that is able to be displayed. inode Converts the value of dot to an inode address. If successful, the current value of inode is updated as well as the value of dot. As a convenient shorthand, if :inode appears at the beginning of the line, the value of dot is set to the current inode and that inode is displayed in inode format. January 1992 7
fsdb(1M) fsdb(1M)ls [-R] [-l] pat1 pat2... Lists directories or files. If no file is specified, the current directory is assumed. Either or both of the options may be used, but if used, must be specified before the filename specifiers. Also, as stated above, wildcard characters are available, and multiple arguments may be given. The long listing shows only the inumber and the name. Use the inode command with `?i' to get more information. override Toggles the value of override. Some error conditions may be overridden if override is toggled on. prompt p Changes the fsdb prompt to p, which must be surrounded by (`` ''). pwd Displays the current working directory. quit Quits fsdb. sb Takes the value of dot as a cylinder group number and then converts it to the address of the superblock in that cylinder group. As a shorthand, :sb at the beginning of a line sets the value of dot to the superblock and displays it in superblock format. ! Escapes to the shell. UFS Inode Commands In addition to the previous commands, several commands deal with inode fields and operate directly on the current inode (they still require the colon (:)). They may be used to display or change the particular fields more easily. The value of dot is only used by the `:db' and `:ib' commands. On completion of the command, the value of dot is changed to point to that particular field. For example, > :ln=+1 increments the link count of the current inode and sets the value of dot to the address of the link-count field. at Indicates access time. bs Indicates block size. ct Indicates creation time. db Uses the current value of dot as a direct block index, where direct blocks number from 0 to 11. In order to 8 January 1992
fsdb(1M) fsdb(1M)display the block itself, you need to pipe this result into the block or fragment command. For example, > 1:db:block,20/X would get the contents of data block field 1 from the inode and convert it to a block address. Then 20 longs are displayed in hexadecimal (see the section ``Formatted Output''). gid Indicates group ID. ib Uses the current value of dot as an indirect block index where indirect blocks number from 0 to 2. This only gets the indirect block itself (the block containing the pointers to the actual blocks). Use the file command and start at block 12 to get to the actual blocks. ln Indicates link count. mt Indicates modification time. md Indicates mode. maj Indicates major device number. min Indicates minor device number. nm Operates on the directory-name field. Once poised at the desired directory entry (using the directory command), this command allows you to change or display the directory name. For example, > 7:dir:nm="foo" gets the seventh directory entry of the current inode and changes its name to foo. Note that names cannot be made larger than the field is set up for. If an attempt is made, the string is truncated to fit and a warning message to this effect is displayed. sz Indicates file size. uid Indicates user ID. SVFS Inode Commands The following mnemonics are used for inode examination and refer to the current working inode: md Indicates mode. January 1992 9
fsdb(1M) fsdb(1M)ln Indicates link count. uid Indicates User ID Number. gid Indicates group ID number. sz Indicates file size. a# Indicates data block numbers (0 to 12). at Indicates access time. mt Indicates modification time. maj Indicates major device number. min Indicates minor device number. gen Indicates generation number. FORMATTED OUTPUT There are two styles and many format types. The two styles are structured and unstructured. Structured output is used to display inodes, directories, superblocks and such. Unstructured output just displays raw data. The following table shows the different ways of displaying: ? c Displays as cylinder groups. i Displays as inodes. d Displays as directories. s Displays as superblocks. / b Displays as bytes. c Displays as characters. o O Displays as octal shorts or longs. d D Displays as decimal shorts or longs. x X Displays as hexadecimal shorts or longs. The format specifier immediately follows the '/' or '?' character. The values displayed by '/b' and all '?' formats are displayed in the current base. Also, type is appropriately updated on completion. EXAMPLES The following two sections list examples of the fsdb command. Examples in the UFS file system are listed first, followed by examples in the SVFS file system. 10 January 1992
fsdb(1M) fsdb(1M)UFS Examples (2000+400%(20+20))=D Displays 2010 in decimal (use of fsdb as a calculator for complex arithmetic). 386:ino?i Displays inumber 386 in an inode format. This now becomes the current inode. :ln=4 Changes the link count for the current inode to 4. :ln=+1 Increments the link count by 1. :ct=X Displays the creation time as a hexadecimal long. :mt=t Displays the modification time in time format. 0:file/c Displays, in ASCII, block 0 of the file associated with the current inode. 2:ino,*?d Displays the directory entries of the first blocks for the root inode of this file system. It stops prematurely if the end-of-file is reached. 5:dir:inode; 0:file,*/c Changes the current inode to that associated with the fifth directory entry (numbered from 0) of the current inode. The first logical block of the file is then displayed in ASCII. :sb Displays the superblock of this file system. 1:cg?c Displays the cylinder-group information and summary for cylinder group 1. 2:inode; 7:dir=3 Changes the inumber for the seventh directory slot in the root directory to 3. 7:dir:nm=name Changes the name field in the directory slot to name. 2:db:block,*?d Displays the third block of the current inode as directory entries. January 1992 11
fsdb(1M) fsdb(1M)3c3:fragment,20:fill=0x20 Gets fragment 3c3 and fills 20 type elements with 0x20. 2050=0xffff Sets the contents of address 2050 to 0xffffffff. 0xffffffff may be truncated depending on the current type. 1c92434= this" is some text" " " Places the ASCII for the string at 1c92434. SVFS Examples 386i Prints inumber 386 in an inode format. This now becomes the current working inode. ln=4 Changes the link count for the working inode to 4. ln=+1 Increments the link count by 1. fc Prints, in ASCII, block 0 of the file associated with the working inode. 2i.fd Prints the first 32 directory entries for the root inode of this file system. d5i.fc Changes the current inode to that associated with the fifth directory entry (numbered from 0) found from the above command. The first logical block of the file is then printed in ASCII. 512B.p0o Prints the superblock of this file system in octal. 2i.a0b.d7=3 Changes the inumber for the seventh directory slot in the root directory to 3. This example also shows how several operations can be combined on one command line. d7.nm= name"" Changes the name field in the directory slot to the given string. Quotes are optional when used with nm if the first character is alphabetic. C2b.p0d Prints the third block of the current inode as directory entries. 12 January 1992
fsdb(1M) fsdb(1M)WARNINGS Extreme caution is advised in determining the availability of fsdb on the system. Suggested permissions are 600 and owned by bin. SEE ALSO fsck(1M) dir(4), fs(4) in A/UX Programmer's Reference January 1992 13