IRIX Base Documentation 2001 May

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Text File | 1998-10-20 | 25.5 KB | 661 lines

ffffssssddddbbbb((((1111MMMM)))) ffffssssddddbbbb((((1111MMMM)))) NNNNAAAAMMMMEEEE fsdb - filesystem debugger for EFS SSSSYYYYNNNNOOOOPPPPSSSSIIIISSSS ffffssssddddbbbb [----????] [----oooo] [----pppp''''_s_t_r_i_n_g''''] [----wwww] _s_p_e_c_i_a_l DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN _f_s_d_b is applicable only to EFS filesystems. _f_s_d_b can be used to patch up a damaged filesystem after a crash. It has conversions to translate block and i-numbers 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 filesystem tree. Because _f_s_d_b reads the disk raw, it is able to circumvent normal filesystem security. It also bypasses the buffer cache mechanism. Hence, it is not advisable to use _f_s_d_b to write to a mounted filesystem. The options available to _f_s_d_b are: ----???? Display usage. ----oooo Override some error conditions. ----pppp''''_s_t_r_i_n_g'''' Set prompt to _s_t_r_i_n_g. ----wwww Open for write. _f_s_d_b contains several error-checking routines to verify inode and block addresses. These can be disabled if necessary by invoking _f_s_d_b with the ----oooo option or by the use of the oooo command. _s_p_e_c_i_a_l is the name of a character device file. _f_s_d_b searches /_e_t_c/_f_s_t_a_b for the raw character device filename, if given the name of a filesystem. 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. Since _f_s_d_b opens the raw device file, any write-throughs bypass the filesystem buffer cache, resulting in a potential mismatch between on-disk and buffer cache data structures. Hence, it is recommended that _f_s_d_b not be used to write to a mounted filesystem. Note that in order to modify any portion of the disk, _f_s_d_b must be invoked with the ----wwww option. Wherever possible, _a_d_b-like syntax was adopted to promote the use of _f_s_d_b through familiarity. Numbers are considered hexadecimal by default. However, the user has control over how data are to be displayed or accepted. The _b_a_s_e 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 PPPPaaaaggggeeee 1111 ffffssssddddbbbb((((1111MMMM)))) ffffssssddddbbbb((((1111MMMM)))) 0000xxxx, decimal numbers with 0000tttt, or octal numbers with 0000. Hexadecimal numbers beginning with aaaa----ffff or AAAA----FFFF must be preceded with 0000xxxx to distinguish them from commands. Disk addressing by _f_s_d_b is at the byte level. However, _f_s_d_b offers many commands to convert a desired inode, directory entry, block, superblock, and so forth to a byte address. Once the address has been calculated, _f_s_d_b records the result in _d_o_t. Several global values are maintained by _f_s_d_b: the current base (referred to as _b_a_s_e), the current address (referred to as _d_o_t), the current inode (referred to as _i_n_o_d_e), the current count (referred to as _c_o_u_n_t), and the current type (referred to as _t_y_p_e). Most commands use the preset value of _d_o_t in their execution. For example, > 2:inode first sets the value of _d_o_t to 2, :::: alerts the start of a command, and the _i_n_o_d_e command sets _i_n_o_d_e to 2. A count is specified after a ,,,,. Once set, _c_o_u_n_t remains at this value until a new command is encountered, which resets the value back to 1 (the default). So, if > 2000,400/X is typed, 400 hexadecimal longs are listed from 2000, and when completed the value of _d_o_t is 2000 + 400 * sizeof (long). If a carriage return is then typed, the output routine uses the current values of _d_o_t, _c_o_u_n_t, and _t_y_p_e and displays 400 more hexadecimal longs. An **** causes the entire block to be displayed. End of block and file are maintained by _f_s_d_b. When displaying data as blocks, an error message is displayed when the end of the block is reached. When displaying data using the _d_b, _d_i_r_e_c_t_o_r_y, or _f_i_l_e commands, an error message is displayed if the end of file is reached. This is needed primarily to avoid passing the end of a directory or file and getting unknown and unwanted results. Examples showing several commands and the use of carriage return are: > 2:ino; 0:dir?d or > 2:ino; 0:db:block?d The two examples are synonymous for getting to the first directory entry of the root of the filesystem. Once there, subsequent carriage returns (or + or -) advance to subsequent entries. Note that: PPPPaaaaggggeeee 2222 ffffssssddddbbbb((((1111MMMM)))) ffffssssddddbbbb((((1111MMMM)))) > 2:inode; :ls / or > 2:inode > :ls / is again synonymous. EEEEXXXXPPPPRRRREEEESSSSSSSSIIIIOOOONNNNSSSS _f_s_d_b recognizes the following symbols. There should be no white space between the symbols and the arguments. ccccaaaarrrrrrrriiiiaaaaggggeeee rrrreeeettttuuuurrrrnnnn Update the value of _d_o_t by the current value of _t_y_p_e and display using the current value of _c_o_u_n_t. #### Numeric expressions can be composed of +, -, *, and % operators (evaluated left to right) and can use parentheses. Once evaluated, the value of _d_o_t is updated. ,,,,_c_o_u_n_t Count indicator. The global value of _c_o_u_n_t is updated to _c_o_u_n_t. The value of _c_o_u_n_t remains until a new command is run. A count specifier of **** attempts to show a _b_l_o_c_k's worth of information. The default for _c_o_u_n_t is 1. ????_f Display in structured style with format specifier _f (see FORMATTED OUTPUT section). ////_f Display in unstructured style with format specifier _f (see FORMATTED OUTPUT section). .... The value of _d_o_t. ++++_e Increment the value of _d_o_t by the expression _e. The amount actually incremented is dependent on the size of _t_y_p_e: dot = dot + e * sizeof (type) The default for _e is 1. ----_e Decrement the value of _d_o_t by the expression _e (see +). ****_e Multiply the value of _d_o_t by the expression _e. Multiplication and division do not use _t_y_p_e. In the above calculation of _d_o_t, consider the sizeof ( _t_y_p_e) to be 1. %%%%_e Divide the value of _d_o_t by the expression _e (see *). PPPPaaaaggggeeee 3333 ffffssssddddbbbb((((1111MMMM)))) ffffssssddddbbbb((((1111MMMM)))) <<<<_n_a_m_e Restore an address saved in register _n_a_m_e. _n_a_m_e must be a single letter or digit. >>>>_n_a_m_e Save an address in register _n_a_m_e. _n_a_m_e must be a single letter or digit. ====_f Display indicator. If _f is a legitimate format specifier (see FORMATTED OUTPUT section), then the value of _d_o_t is displayed using format specifier _f. Otherwise, assignment is assumed (see next item). ====[_e] ====[_s] Assignment indicator. The address pointed to by _d_o_t 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 Incremental assignment. The address pointed to by _d_o_t has its contents incremented by expression _e. ====----_e Decremental assignment. The address pointed to by _d_o_t has its contents decremented by expression _e. CCCCOOOOMMMMMMMMAAAANNNNDDDDSSSS A command must be prefixed by a :::: character. Only enough letters of the command to uniquely distinguish it are needed. Multiple commands can be entered on one line by separating them by a space, tab, or ;;;;. In order to view a potentially unmounted disk in a reasonable manner, _f_s_d_b offers the _c_d, _p_w_d, _l_s, and _f_i_n_d commands. The functionality of these commands substantially matches those of its IRIX counterparts (see individual commands for details). The ****, ????, and [[[[----]]]] wildcard characters are available. bbbbaaaasssseeee====_b Display or set base. As stated above, all input and output is governed by the current _b_a_s_e. If the ====bbbb is left off, the current _b_a_s_e is displayed. Otherwise, the current _b_a_s_e is set to _b. Note that this is interpreted using the old value of _b_a_s_e. To ensure correctness, use the 0000, 0000tttt, or 0000xxxx prefix when changing the _b_a_s_e. The default for _b_a_s_e is hexadecimal. bbbblllloooocccckkkk Convert the value of _d_o_t to a block address. ccccdddd _d_i_r Change the current directory to directory _d_i_r. The current values of _i_n_o_d_e and _d_o_t are also updated. If no _d_i_r is specified, then change directories to inode 2 (////). ccccgggg Convert the value of _d_o_t to a cylinder group. PPPPaaaaggggeeee 4444 ffffssssddddbbbb((((1111MMMM)))) ffffssssddddbbbb((((1111MMMM)))) _d_i_r_e_c_t_o_r_y If the current _i_n_o_d_e is a directory, then the value of _d_o_t is converted to a directory slot offset in that directory. _d_o_t now points to this entry. _f_i_l_e The value of _d_o_t is taken as a relative block count from the beginning of the file. The value of _d_o_t is updated to the first byte of this block. ffffiiiinnnndddd _d_i_r [----nnnnaaaammmmeeee _n] [----iiiinnnnuuuummmm _i] Find files by name or i-number. _f_i_n_d recursively searches directory _d_i_r and below for filenames whose i-number matches _i or whose name matches pattern _n. Note that only one of the two options (----nnnnaaaammmmeeee or ----iiiinnnnuuuummmm) can be used at one time. Also, the ----pppprrrriiiinnnntttt is not needed or accepted. ffffiiiillllllll====_p Fill an area of disk with pattern _p. The area of disk is delimited by _d_o_t and _c_o_u_n_t. _i_n_o_d_e Convert the value of _d_o_t to an inode address. If successful, the current value of _i_n_o_d_e is updated as well as the value of _d_o_t. As a convenient shorthand, if ::::iiiinnnnooooddddeeee appears at the beginning of the line, the value of _d_o_t is set to the current _i_n_o_d_e and that inode is displayed in inode format. llllssss [----RRRR] [----llll] _p_a_t_1 _p_a_t_2 ... List directories or files. If no file is specified, the current directory is assumed. Either or both of the options can be used (but, if used, must be specified before the filename specifiers). Also, as stated above, wildcard characters are available and multiple arguments can be given. The long listing shows only the i-number and the name; use the _i_n_o_d_e command with ????iiii to get more information. The output is sorted in alphabetical order. If either the ----RRRR or the ----llll options is used, then the files can have a character following the filename, indicating the type of the file. Directories have a ////, symbolic links have a @@@@, AF_UNIX address family sockets have a ==== and fifos have an ffff. Regular files and block and character device files have an **** if they are executable. If the file type is unknown, then a ???? is printed. oooovvvveeeerrrrrrrriiiiddddeeee Toggle the value of override. Some error conditions can be overridden if override is toggled on. pppprrrroooommmmpppptttt _p Change the _f_s_d_b prompt to _p. _p must be surrounded by double quotes ("). ppppwwwwdddd Display the current working directory. qqqquuuuiiiitttt Quit _f_s_d_b. PPPPaaaaggggeeee 5555 ffffssssddddbbbb((((1111MMMM)))) ffffssssddddbbbb((((1111MMMM)))) ssssbbbb The value of _d_o_t is taken as the basic block number and then converted to the address of the superblock in that cylinder group. As a shorthand, ::::ssssbbbb at the beginning of a line sets the value of _d_o_t to the superblock and displays it in superblock format. !!!! sssshhhh Escape to shell. IIIINNNNOOOODDDDEEEE CCCCOOOOMMMMMMMMAAAANNNNDDDDSSSS In addition to the above commands, there are several commands that deal with inode fields and operate directly on the current _i_n_o_d_e (they still require the ::::). They can be used to display more easily or change the particular fields. The value of _d_o_t is only used by the ::::ddddbbbb, ::::lllleeeennnn, and ::::ooooffffffff commands. Upon completion of the command, the value of _d_o_t is changed to point to that particular field. For example, > :ln=+1 increments the link count of the current _i_n_o_d_e and set the value of _d_o_t to the address of the link count field. It is important to know the format of the disk inode structure and the size and alignment of the respective fields; otherwise the output of these commands is not coherent. The disk inode structure is available in <_s_y_s/_f_s/_e_f_s__i_n_o._h>. aaaatttt Access time. cccctttt Creation time. ddddbbbb Use the current value of _d_o_t as an index into the list of extents stored in the disk inode to get the starting disk block number associated with the corresponding extent. Extents number from 0 to 11. In order to display the block itself, you need to pipe this result into the _b_l_o_c_k command. For example, > 1:db:block,20/X gets the contents of disk block number field of extent number 1 from the inode and converts it to a block address. Twenty longs are then displayed in hexadecimal (see the FORMATTED OUTPUT section). ggggeeeennnn Inode generation number. ggggiiiidddd Group ID. llllnnnn Link count. lllleeeennnn Use the current value of _d_o_t as an index into the list of extents stored in the disk inode to get the length associated with the corresponding extent. Extents number from 0 to 11. This field is one byte long. For example, PPPPaaaaggggeeee 6666 ffffssssddddbbbb((((1111MMMM)))) ffffssssddddbbbb((((1111MMMM)))) > 1:len/b displays the contents of the len field of extent number 1. mmmmtttt Modification time. mmmmdddd Mode. mmmmaaaajjjj Major device number. mmmmiiiinnnn Minor device number. nnnneeeexxxx Number of extents. nnnnmmmm Although listed here, this command actually operates on the directory name field. Once poised at the desired directory entry (using the _d_i_r_e_c_t_o_r_y 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 _i_n_o_d_e and changes its name to foo. Names have to be the same size as the original name. If the new name is smaller, it is padded with ####. If it is larger, the string is truncated to fit and a warning message to this effect is displayed. ooooffffffff Use the current value of _d_o_t as an index into the list of extents stored in the disk inode to get the logical block offset associated with the corresponding extent. Extents number from 0 to 11. This field is three bytes long. For example, > 3:off,3/b displays the contents of the off field of extent number 3. sssszzzz File size. uuuuiiiidddd User ID. FFFFOOOORRRRMMMMAAAATTTTTTTTEEEEDDDD OOOOUUUUTTTTPPPPUUUUTTTT 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 the like. Unstructured output only displays raw data. The following table shows the different ways of displaying: PPPPaaaaggggeeee 7777 ffffssssddddbbbb((((1111MMMM)))) ffffssssddddbbbb((((1111MMMM)))) ???? cccc Display as cylinder groups iiii Display as inodes IIII Display as inodes (all direct extents) dddd Display as directories ssss Display as superblocks eeee Display as extents //// bbbb Display as bytes cccc Display as characters oooo OOOO Display as octal shorts or longs dddd DDDD Display as decimal shorts or longs xxxx XXXX Display as hexadecimal shorts or longs The format specifier immediately follows the //// or ???? character. The values displayed by ////bbbb and all ???? formats are displayed in the current _b_a_s_e. Also, _t_y_p_e is appropriately updated upon completion. EEEEXXXXAAAAMMMMPPPPLLLLEEEESSSS > :base Display the current input/output base (hexadecimal by default). > :base=0xa Change the current input/output base to decimal. > 0t2000+(0t400%(0t20+0t20))=D Display 2010 in decimal (use of _f_s_d_b as a calculator for complex arithmetic). The 0000tttt indicates that the numbers are to be interpreted as decimal numbers and are necessary only if the current base is not decimal. Brackets should be used to force ordering since _f_s_d_b does not force the normal ordering of operators. Note that %%%% is the division symbol. > 386:ino?i Display i-number 386 in an inode format. This now becomes the current _i_n_o_d_e. > :ln=4 Change the link count for the current _i_n_o_d_e to 4. > :ln/x Display the link count as a hexadecimal short. > :ln=+1 Increment the link count by 1. > :sz/D Display the size field as a decimal long. > :sz/X Display the size field as a hexadecimal long. > :ct=X Display the creation time as a hexadecimal long. > :mt=t Display the modification time in time format. PPPPaaaaggggeeee 8888 ffffssssddddbbbb((((1111MMMM)))) ffffssssddddbbbb((((1111MMMM)))) > 0:db,3/b Display the block number of the first extent as 3 bytes. The block number has to be printed out as bytes, because of alignment considerations. > 0:file/c Display, in ASCII, block zero of the file associated with the current _i_n_o_d_e. > 5:dir:inode; 0:file,*/c Change the current inode to that associated with the fifth directory entry (numbered from zero) of the current _i_n_o_d_e. The first logical block of the file is then displayed in ASCII. > :sb Display the superblock of this filesystem. > 0:cg?c Display cylinder group information and summary for the first cylinder group (cg number 0). > 7:dir:nm="name" Change the name field in the directory slot to _n_a_m_e. > 2:db:block,*?d Display the third block of the current _i_n_o_d_e as directory entries. > 0:db=0x43b Change the disk block number associated with extent 0 of the inode to 0x43b. > 0:len=0x4 Change the length of extent 0 to 4. > 1:off=0xa Change the logical block offset of extent 1 to 4. > 0x43b:block/X Display the first four bytes of the contents of block 0x43b. > 0x43b:block=0xdeadbeef Set the contents of disk block number 0x43b to 0xdeadbeef. 0xdeadbeef may be truncated depending on the current _t_y_p_e. > 2050=0xffffffff Set the contents of address 2050 to 0xffffffff. 0xffffffff may be truncated depending on the current _t_y_p_e. > 1c92434="this is some text" Place the ASCII for the string at 1c92434. > 2:inode:0:db:block,*?d Change the current inode to 2. Take the first block associated with this (root) inode and display its contents as directory entries. It stops prematurely if PPPPaaaaggggeeee 9999 ffffssssddddbbbb((((1111MMMM)))) ffffssssddddbbbb((((1111MMMM)))) the EOF is reached. SSSSEEEEEEEE AAAALLLLSSSSOOOO fsck(1M), dir(4), efs(4), inode(4). PPPPaaaaggggeeee 11110000