DEBUGVMFS6(8)

NAME
debugvmfs6 - VMFS file system debugger

SYNOPSIS

debugvmfs6 VOLUME... COMMAND [ OPTIONS ] debugvmfs6 -b BITMAP show [ VARIABLE ]

DESCRIPTION

The debugvmfs6 program allows to display various informations about VMFS6 file systems, and to access data within the file systems.

The VOLUME to be opened can be either a block device or an image file. When the VMFS spreads accross several extents, all extents must be given.

Please note that most commands are still likely to change in future versions.

When given the -b option, a BITMAP file may directly be opened from the host file system. In this mode, only the show command is supported, and the variables available are only a subset.

SPECIFYING FILES

Some commands take a filespec as an argument. A filespec may take either of the following forms:

    • A path name, relative to the root of the filesystem if it starts with '/', or relative to the current working directory otherwise (interactive mode only).

    • An inode number, enclosed between angle brackets, e.g. '<4>', '<0x1400004>'

COMMANDS

cat filespec [ ... ]
    Outputs the content of the given files from the VMFS.

ls [ -l ] filespec
    Lists files contained at the given location within the VMFS.

    With -l, gives some more information, much like the output from ls(1) when given the -l option.

truncate filespec length
    Truncate the file to the specified length. R/W support must be enabled.

chmod filespec mode
    Change file permissions to the given mode.

df
    Outputs information about file system size.

get_file_block filespec position
    Get file block corresponding to position in the specified file.

check_vol_bitmaps
    Checks volume bitmaps consistency.

show_heartbeats
    Outputs active heartbeats on the file system.

read_block block_id [ ... ]
    Outputs content within the specified block_id in binary

get_block_status block_id
    Get status (allocated or free) of the specified block_id.

alloc_block_fixed block_id
    Allocate the specified block_id. R/W support must be enabled.

alloc_block block_type
    Allocate a block of the specified type. R/W support must be enabled.

    Allowed block types are: 1 (File Block), 2 (Sub-Block), 3 (Pointer Block) and 4 (File Descriptor / Inode).

free_block block_id
    Free the specified block_id. R/W support must be enabled.

    Warning: can cause damage since no heartbeat is used at this time and a block used by a file can be freed.

show
    Display value(s) of the given variable. See the VARIABLES section for more details. When no variable is given, it lists the top-level properties.

shell
    Starts an interactive session. All of the above commands can be executed from within the interactive session.

    The current working directory can be changed with the cd command, followed by a filespec.

    The following output redirections are supported within the shell:

        • cmd > output

        Puts the output of cmd in the output file.

        • cmd >> output

        Appends the output of cmd to the output file.

        • cmd | external command

        Sends the output of cmd to the input of external command. The external command itself can contain output redirection.

        Examples:

            • read_block 0x00000681 | less

            • cat /.fdc.sf | hexdump -C

            • cat /.fdc.sf | hexdump -C > /tmp/fdc.hex

            • cat /.fdc.sf | hexdump -C | less

VARIABLES

Variables in debugvmfs6 represent structures on the filesystem. The currently supported top-level variables are the following:

    • vol_version

    • version

    • label

    • mode

    • uuid

    • ctime

    • block_size

    • subblock_size

    • fdc_header_size

    • fdc_bitmap_count

    • fbb

    • fdc

    • pbc

    • sbc

    • fs

    • lvm

    • blkid[blk]

    • dirent["path"]

    • inode["filespec"]

The vol_version, version, label, mode, uuid, ctime, block_size, subblock_size, fdc_header_size, and fdc_bitmap_count properties are low-level information about the filesystem.

The fbb, fdc, pbc and sbc variables are bitmaps. Running them through the show command will display all the bitmaps header fields. Each of these fields can also be displayed individually:

    • bitmap.items_per_bitmap_entry

    • bitmap.bmp_entries_per_area

    • bitmap.hdr_size

    • bitmap.data_size

    • bitmap.area_size

    • bitmap.area_count

    • bitmap.total_items

    • bitmap.used_items

    • bitmap.free_items

    • bitmap.entry[n]

e.g. to display the data size of the fdc bitmap, type show fdc.data_size.

Each bitmap.entry[n] (where 0 ≤ n < bitmap.bmp_entries_per_area * bitmap.area_count) contains information about each entry in the bitmap. The available fields are:

    • bitmap.entry[n].id

    • bitmap.entry[n].total

    • bitmap.entry[n].free

    • bitmap.entry[n].ffree

    • bitmap.entry[n].mdh

    • bitmap.entry[n].item[m]

The bitmap.entry[n].mdh is a metadata header. See further below for more details about metadata headers.

Each bitmap.entry[n].item[m] (where 0 ≤ m < bitmap.items_per_bitmap_entry) contains information about a given item in the given entry. The available fields are:

    • bitmap.entry[n].item[m].used

    • bitmap.entry[n].item[m].dump

The pbc bitmap has an additional field:

    • pbc.entry[n].item[m].blocks

The lvm variable contains low-level information about the physical and logical volumes. The available fields are:

    • lvm.uuid

    • lvm.size

    • lvm.blocks

    • lvm.num_extents

    • lvm.extent[n]

Each lvm.extent[n] (where 0 ≤ n < lvm.num_extents) contains low-level information about the physical volumes. The available fields are:

    • lvm.extent[n].device

    • lvm.extent[n].uuid

    • lvm.extent[n].lun

    • lvm.extent[n].version

    • lvm.extent[n].name

    • lvm.extent[n].size

    • lvm.extent[n].num_segments

    • lvm.extent[n].first_segment

    • lvm.extent[n].last_segment

Each blkid[blk] (where blk is a block id) contains information on the given block id. The available fields are:

    • blkid[blk].item

    • blkid[blk].flags

Each dirent[path] (where path is a path relative to the current directory in the shell or / outside the shell) contains information on the directory entry corresponding to the given path. The available fields are:

    • dirent["path"].type

    • dirent["path"].block_id

    • dirent["path"].record_id

    • dirent["path"].name

Each inode[filespec] contains information on the inode corresponding to the given filespec. The available fields are:

    • inode["filespec"].id

    • inode["filespec"].id2

    • inode["filespec"].nlink

    • inode["filespec"].type

    • inode["filespec"].flags

    • inode["filespec"].size

    • inode["filespec"].blk_size

    • inode["filespec"].blk_count

    • inode["filespec"].uid

    • inode["filespec"].gid

    • inode["filespec"].mode

    • inode["filespec"].zla

    • inode["filespec"].tbz

    • inode["filespec"].cow

    • inode["filespec"].atime

    • inode["filespec"].mtime

    • inode["filespec"].ctime

    • inode["filespec"].rdm_id

    • inode["filespec"].mdh

    • inode["filespec"].blocks

Metadata headers are being used in several places, such as bitmap.entry[n].mdh and inode["filespec"].mdh. They mostly contain information about clustered accesses to metadata on the filesystem. The available fields are:

    • mdh.magic

    • mdh.pos

    • mdh.hb_pos

    • mdh.hb_lock

    • mdh.hb_uuid

    • mdh.hb_seq

    • mdh.obj_seq

    • mdh.mtime

Variable values can also be used in expressions using square brackets to use the variable value as an index. For example:

    • blkid[inode["filespec"].id]

Enclosing a variable name with parentheses will use that variable value as a variable name. For example:

    • (blkid[blk].item).status

When invoked with the -b option, the top-level variables are those normally under bitmap:

    • items_per_bitmap_entry

    • bmp_entries_per_area

    • hdr_size

    • data_size

    • area_size

    • area_count

    • total_items

    • used_items

    • free_items

    • entry[n]

The sub-variables for each entry are also available.

AUTHORS

Christophe Fillot <cf@utc.fr[1]>, Mike Hommey <mh@glandium.org[2]> Weafon Tsao <weafon.tsao@accelstor.com[3]> Thomas Ward <teward@ubuntu.com[4]>

SEE ALSO

vmfs6-fuse(8)

NOTES

1.  cf@utc.fr
    mailto:cf@utc.fr

2.  mh@glandium.org
    mailto:mh@glandium.org

3.  weafon.tsao@accelstor.com
    mailto:weafon.tsao@accelstor.com

4.  teward@ubuntu.com
    mailto:teward@ubuntu.com