fsdb_vxfs(1M)

NAME

fsdb_vxfs: fsdb — VxFS file system debugger

SYNOPSIS

fsdb [-F vxfs] [-z inumber] special

DESCRIPTION

fsdb can analyze VxFS file system problems or repair a damaged VxFS file system after a crash. A special device special specifies the file system to debug. The fsdb command is intended for experienced users only.

fsdb can convert block and inumbers into their corresponding disk addresses. In addition, mnemonic offsets allow access to different parts of an inode. These greatly simplify the process of correcting control block entries or descending the file system tree.

By default, numbers are considered decimal. You must prefix octal numbers with 0, and prefix hexadecimal numbers with 0x. When using hexadecimal numbers, it is preferable to follow the number with a space, because several commands are letters that are also hexadecimal digits. In this document a pound sign (#) indicates that a number is to be specified.

fsdb reads a block at a time and works with raw and block I/O. All I/O is unbuffered, so changes made to the file system are immediate and changes made by other processes or by the kernel are immediately seen by fsdb.

Options

fsdb recognizes the following options:

generic_options: Supported by the generic fsdb command. See fsdb(1M).
-F vxfs: Specify the VxFS file-system type.
-z inumber: Clear the inode identified by inumber (non-interactive). Multiple -z options accumulate.

Operands

fsdb recognizes the following operand:

special: Name of the special device that contains the VxFS file system to debug.

Using Commands and Symbols

It is best to separate each token on a command line with a space. Although the command parser does not require element separation, there is no ambiguity in the command language if each token is separated with a space. For example, the command 0x23b b sets the current position to block 0x23b hexadecimal. The command 0x23bb is invalid, because the command is parsed as simply a hexadecimal number. The command 23b positions to block 23 decimal, since the command is not ambiguous.

You can separate commands with new lines. You can put multiple commands on one line and separate them with a dot (.) or a semicolon (;) If multiple commands are placed on one line, generally only the last command displays results. This allows positioning commands to be followed by printing commands or change commands without intermediate printing.

Symbols for the fsdb Command

The following symbols are recognized by the fsdb command:

h[mod|print]: Print summary of commands that display [modify|format] the file system.
?[mod|print]: Print summary of commands that display [modify|format] the file system.
help[mod|print]: Print summary of commands that display [modify|format] the file system.
!: Escape to shell.
|: Pipe output of fsdb to a shell command.
q: Quit.
string: A character string. Inside a character string, a NULL character can be specified with ``\0''; a double quote can be specified with ``\"''; and a backslash can be specified with ``\\ ''.
+ - * / %: Add, subtract, multiply, divide, and modulus.
=: Assignment
i: An inode in the primary inode list.
ai: An inode in the attribute inode list.
au: An allocation unit.
b: A block.
im: The immediate data area of an inode. Small directories and symbolic link files (96 bytes or less) are stored directly in the inode itself, in the area normally occupied by data block numbers and extent sizes.
attr: An attribute inode.
cdb: Current directory block.
d: A directory entry.
a: An inode address entry.
B: A byte.
H: A half-word (2 bytes)
W: A word (4 bytes)
D: A double-word (8 bytes)
p: General print facility
calc: Simple calculator and base converter
find: Find a matching pattern in the file system
fset: A fileset.
iau: An inode allocation unit in the primary inode list.
aiau: An inode allocation unit in the attribute inode list.
cut: The current usage table.
olt: The object location table.
mapi: Map logical file offset to an inode extent.
reset: Reset device.

Print Facility Print Formats

The print facility recognizes the following print formats:

S: Print as a super-block.
A: Print as an allocation-unit header.
AS: Print as an auxiliary super-block.
L: Print as intent-log records.
I: Print as inodes.
ST: List state table blocks.
T: Print as typed extent descriptors.
dent: Print as directory entries.
db: Print as a directory block.
dh: Print as a directory header.
o: Print as octal words.
oB oH oW oD: Print as octal bytes, half-words, words, or double-words.
x: Print as hexadecimal words.
xB xH xW xD: Print as hexadecimal bytes, half-words, words, or double-words.
e: Print as decimal words.
eB eH eW eD: Print as decimal bytes, half-words, words, or double-words.
u: Print as unsigned words.
uB uH uW uD: Print as unsigned bytes, half-words, words, or double-words.
c: Print as characters.
F: Print as fileset headers.
C: Print as current usage table entries.
IA: Print as an inode allocation unit header.
oltext: Print as an object location table extent.
Q: Prints as a BSD quota record.
DV: Print as a device record.

Symbols in Inode Fields

Changes to inode fields can be made symbolically. The following symbols represent inode fields:

md: Inode mode field
ln: Inode link count field
uid: Inode user ID Number field
gid: Inode group ID Number field
szlo: Low-order word of inode file size field
szhi: High-order word of inode file size field
sz: Inode file size field
de#: Inode direct extent data block numbers (0 - 9)
des#: Inode direct extent sizes (0 - 9)
ie#: Inode indirect extent data block numbers (0 - 1)
ies: Inode indirect extent size
at: Inode access time field (seconds)
ats: Inode access time field (microseconds).
ct: Inode change time field (seconds).
cts: Inode change time field (microseconds).
mt: Inode modification time field (seconds).
mts: Inode modification time field (microseconds).
af: Inode allocation flags field.
gen: Inode generation count field.
org: Inode mapping type field.
fe: Inode fixed extent size field.
bl: Inode blocks held field.
eopflg: Inode extended operation flag field.
eopdat: Inode extended operation data field.
rdev: If device, inode device number.
maj: If device, inode major number.
min: If device, inode minor number.
pd: If directory, inode parent directory.
res: If regular file, inode reservation.
verhi: Inode high-order word of serial number.
verlo: Inode low-order word of serial number.
fsindex: Referencing fileset ID.
matching: Inode number of matching inode.
iano: Indirect attribute inode.

Symbols for Directory Block Fields

Changes to directory block fields can be made symbolically. The following symbols represent directory block fields:

tfree: Total free space (only if in a data block).
hash#: Hash chain start (0 through 31, only if in a data block).
d#: Directory entry (variable number of entries).
nhash: Number of hash chains.

Symbols for Directory Entry Fields

Changes to directory entry fields can be made symbolically. The following symbols represent directory entry fields:

ino: Inode number
nm: Entry name
nmlen: Name length
reclen: Record length (only if in a data block)
hnext: Name hash next (only if in a data block)

Positions in File Systems and Positioning Commands

fsdb maintains several positions in the file system:

current position
current primary-inode position (i)
current attribute-inode position (ai)
current inode type (i or ai)
current fileset-header position (fset)
current allocation-unit position (au)
current primary-inode allocation-unit (iau) position
current inode allocation-unit type (iau or aiau)
current attribute-inode allocation-unit (aiau) position

These are used by various fsdb commands. (The au positions are only supported on the Version 2 disk layout.)

The following commands are supported:

# B|H|W|D: Set the current position in the file system to the specified offset in bytes, half-words, words, or double-words. If it is the last command on a line, print the byte, half-word, word, or double-words in hexadecimal.
+|- # B|H|W|D: Set the current position to the specified relative offset in bytes, half-words, words, or double-words. If it is the last command on a line, print the byte, half-word, word, or double-words in hexadecimal.
# au: Set the current position in the file system to the specified allocation unit (au) position. Set the current allocation unit position to the resulting offset. If it is the last command on a line, print the allocation unit header.
+|- # au: Set the current position in the file system to the specified position relative to the current allocation unit (au) position. Set the current allocation unit position to the resulting offset. If it is the last command on a line, print the allocation unit header.
au: Set the current position in the file system to the current allocation unit position. If it is the last command on a line, print the allocation unit header.
# b: Set the current position in the file system to the specified offset in blocks. Set the current block position to the resulting offset. The block size is the block size of the file system. If it is the last command on a line, print the first word in the block in hexadecimal.
+|- # b: Set the current position to specified relative offset in blocks. Set the current block position to the resulting offset. If it is the last command on a line, print the first word in the block in hexadecimal.
b: Set the current position to current block position (the block specified by the last [+|-] # b operation). If it is the last command on a line, print the first word in the block in hexadecimal.
cut: Set the current position to the current usage table (cut). If it is the last command on a line, print the first current usage table entry.
dev: Set the current position to the primary device's configuration record. If it is the last command on a line, print the device-configuration record.
# fset: Set the current position in the file system to the fileset header entry for the specified fileset index. Set the current fileset position to the resulting offset. If it is the last command on a line, print the specified fileset header.
+|- # fset: Set the current position in the file system to the fileset header entry for the specified position relative to the current fileset position. Set the current fileset position to resulting offset. If it is the last command on a line, print the specified fileset header.
fset: Set the current position in the file system to the current fileset position. If it is the last command on a line, print the fileset header for the current fileset.
# aiau: Set the current position in the file system to the specified attribute inode allocation unit (aiau) in a fileset. Set the current attribute inode allocation unit position to the resulting offset. If it is the last command on a line, print the attribute inode allocation unit header.
+|- # aiau: Set the current position in the file system to the specified position relative to the current attribute inode allocation unit (aiau) position. Set the current attribute inode allocation unit position to the resulting offset. If it is the last command on a line, print the attribute inode allocation unit header.
aiau: Set the current position in the file system to the current attribute inode allocation unit (aiau) position. If it is the last command on a line, print the attribute inode allocation unit header.
# iau: Set the current position in the file system to the specified inode allocation unit (iau) in a fileset. Set the current inode allocation unit position to the resulting offset. If it is the last command on a line, print the inode allocation unit header.
+|- # iau: Set the current position in the file system to the specified position relative to the current inode allocation unit (iau) position. Set the current inode allocation unit position to the resulting offset. If it is the last command on a line, print the inode allocation unit header.
iau: Set the current position in the file system to the current inode allocation unit (iau) position. If it is the last command on a line, print the inode allocation unit header.
# ai: Set the current position in the current fileset to the ilist entry for the specified attribute inode. Set the current attribute inode position to the resulting offset. If it is the last command on a line, print the ilist entry for the inode.
+|- # ai: Set the current position in the current fileset to the ilist entry for the specified relative attribute inode. Set the current attribute inode position to the resulting offset. If it is the last command on a line, print the ilist entry for the inode.
ai: Set the current position in the current fileset to the current attribute inode position. If it is the last command on a line, print the ilist entry for the inode.
# i: Set the current position in the current fileset to the ilist entry for the specified inode. Set the current inode position to the resulting offset. If it is the last command on a line, print the ilist entry for the inode.
+|- # i: Set the current position in the current fileset to the ilist entry for the specified relative inode. Set the current inode position to the resulting offset. If it is the last command on a line, print the ilist entry for the inode.
i: Set the current position in the current fileset to the current inode position. If it is the last command on a line, print the ilist entry for the inode.
a#: Set the current position to specified offset in blocks specified by the inode address #. Addresses 0 through 9 are for direct extents ( de ). Addresses 10-11 are for indirect extents ( ie ). The addresses are displayed when printing an ilist entry. Set the current block position to the resulting offset. If it is the last command on a line, print the first word in the block in hexadecimal.
im: Set the current position to immediate data area of the current inode. Set the current block position to the resulting offset. If it is the last command on a line, print the first word of the area in hexadecimal.
attr: Set the current position to attribute data area of the current inode. Set the current block position to the resulting offset. If it is the last command on a line, print the first word in the block in hexadecimal.
# B|H|W|D =# [#]: Set the current position and change the number at the specified offset to the given number. If a double-word offset is specified, then two numbers separated by a space are required. The resulting value is printed in hexadecimal.
+|-# B|H|W|D =# [#]: Set the current position and change the number at the specified relative offset to the given number. If a double-word offset is specified, then two numbers separated by a space are required. The resulting value is printed in hexadecimal.
# B|H|W|D = string: Set the current position and change the characters at the specified offset to the given string. The resulting value is printed as a character string.
+|- # B|H|W|D = string: Set the current position and change the characters at the specified relative offset to the given string. The resulting value is printed as a character string.
olt: Set the current position to the object location table (olt). If it is the last command on a line, print the object location table.
p [#] format: Print the contents of the file system at the current offset as the specified number of entries of a given format. The allowable print formats are specified above. If a number of entries to print is not specified, one entry is printed.
inode_field = #: Set the contents of the given inode field to the specified number. The current inode specifies the inode list entry to be modified. The symbols representing inode fields are listed above.
directory_block_field = #: Set the contents of the given directory block field to the specified number. The current block is treated as a directory block and the offset in that block which is represented by the given field is changed. The symbols representing directory block fields are listed above.
d#: Set the current directory entry to the specified number. The current block is treated as a directory block. If the current block is an immediate data area for an inode, then the block is treated as containing immediate directory entries. If it is the last command on a line, the directory entry at the resulting offset is printed.
directory_entry_field = #: Set the contents of the given directory field to the specified number. The current directory entry specifies where the directory entry is located. The resulting value is printed in hexadecimal.
nm = string: Set the directory name field of the current directory entry to the specified string. The resulting value is printed as a character string.
calc # [+|-|*|/ #]: Take a number or the sum, difference, product or dividend of two numbers and print in decimal, octal, hexadecimal and character format.
find # B|H|W|D [#]: Search for the given numeric pattern in the file system. The size of the object to match is specified. If a double-word is specified, then two numbers must be given. The search is performed forward from the current offset. A maximum number of blocks to search can be specified. If found, the location and value are printed in hexadecimal.
find string [#]: Search for the given character string in the file system. The search is performed forward from the current offset. A maximum number of blocks to search can be specified. If found the location and string are printed.
fmtlog: Format all intent log entries. A completely formatted intent log can be quite lengthy. It is a good idea use the fsdb command as a filter and redirect the output to a file or pager to look at a complete log format.
listfset: List all filesets by their indexes and names.
mapi #: Treat the number as a logical offset in the file described by the current inode, and print the extent that it maps to.
reset: Does the equivalent of exiting fsdb and restarting on same device.

Help Commands

The following help commands are supported:

h|help: Display primary help screen.
h mod: Display modification-commands help screen.
h print: Display print-commands help screen.

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.
8192B.p S: Prints the super-block of this file system symbolically.
d7.nm = foo: Changes the name field in the directory slot to foo.
2i.a0.d7.ino = 3: Changes the inumber for the seventh directory slot in the root directory to three (also shows how to combine several operations on one command line)
23i.im.d5: Prints the sixth directory entry in the immediate area of inode 23.

WARNINGS

Always run a file system check (see fsck(1M)) after using the fsdb command to modify a file system. (Use fsck -o full,nolog.)

Some aspects of fsdb apply to a specific VxFS disk layout version.