Transcript Document

• fsck
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IBM AIX - POWER/PowerPC-based systems
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It was the first Operating System to
introduce the idea of a journaling file
system, JFS, which allowed for fast
boot times by avoiding the need to
ensure the consistency of the file
systems on disks (see fsck) on every
reboot
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Git (software) - Characteristics
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To check integrity, run the
git fsck command.
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inode - Practical considerations
Many computer programs used by
system administrators in UNIX
Operating Systems often designate files
with inode numbers. Examples include
popular disk integrity checking utilities
such as the fsck or pfiles. Thus, the need
naturally arises to translate inode
numbers to file pathnames and vice
versa. This can be accomplished using
the file finding utility find with the -inum
option, or the ls command with the
proper option (-i on POSIX compliant
platforms).
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Btrfs - Checking and recovery
Unix systems traditionally rely on
"fsck" programs to check and repair
filesystems. The btrfsck program is
now available but, as of May 2012, it is
described by the authors as
"relatively new code" which has "not
seen widespread testing on a large
range of real-life breakage", and that
"may cause additional damage in the
process of repair".
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Hard disk drive - Integrity and failure
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For logical damage to file systems, a
variety of tools, including fsck on
UNIX-like systems and CHKDSK on
Windows, can be used for data
recovery
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Unix - Components
System utilities –
administrative tools such
as mkfs, fsck, and many
others.
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ext3 - Advantages
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The ext2 and ext3 file systems share the
same standard set of utilities, e2fsprogs,
which includes an fsck tool
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ext3 - Functionality
ext3, like most current Linux
filesystems, cannot be fsck-ed while
the filesystem is mounted for writing.
Attempting to check a file system that
is already mounted may detect bogus
errors where changed data has not
reached the disk yet, and corrupt the
file system in an attempt to "fix" these
errors.
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IBM AIX (operating system) - POWER/PowerPC-based systems
It was the first Operating System to
introduce the idea of a journaling file
system, IBM Journaled File System 2
(JFS2)|JFS, which allowed for fast boot
times by avoiding the need to ensure the
consistency of the file systems on disks
(see fsck) on every reboot
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Kyoto Cabinet - Practical functionality
If inconsistency of the database is
detected when opening the database,
all regions are scanned as with fsck
and the database is reconstructed with
surviving records implicitly.
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Lustre (file system) - History
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This contract covered the completion of features,
including improved Single Server Metadata
Performance scaling, which allows Lustre to better
take advantage of many-core metadata server;
online Lustre distributed filesystem checking
(LFSCK), which allows verification of the
distributed filesystem state between data and
metadata servers while the filesystem is mounted
and in use; and Distributed Namespace (DNE),
formerly Clustered Metadata (CMD), which allows
the Lustre metadata to be distributed across
multiple servers
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Lustre (file system) - Release history
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The MDS LFSCK feature can verify
and repair the Object Index (OI) file
while the file system is in use, after a
file-level backup/restore or
corruption
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Lustre (file system) - Release history
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The LFSCK feature allows scanning
and verifying the internal consistency
of the MDT FID and LinkEA attributes
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ZFS - Resilvering and scrub
ZFS has no fsck repair tool equivalent,
common on Unix filesystems, which does
file system validation and file system
repair.No fsck utility equivalent exists for
ZFS. This utility has traditionally served
two purposes, those of file system repair
and file system validation. Instead, ZFS
has a repair tool called scrub which
examines and repairs silent corruption and
other problems. Some differences are:
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ZFS - Resilvering and scrub
* fsck must be run on an offline
filesystem, which means the filesystem
must be unmounted and is not usable
while being repaired.
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ZFS - Resilvering and scrub
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* fsck usually only checks metadata (such
as the journal log) but never checks the
data itself. This means, after an fsck, the
data might still be corrupt.
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ZFS - Resilvering and scrub
* scrub checks everything, including
metadata and the data. The effect can be
observed by comparing fsck to scrub times
— sometimes a fsck on a large RAID
completes in a few minutes, which means
only the metadata was checked.
Traversing all metadata and data on a
large RAID takes many hours, which is
exactly what scrub does.
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Unix File System - Implementations
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To overcome the remaining issues after a
failure, a background fsck utility was
introduced.
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Unix File System - Implementations
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FreeBSD 9.0 adds support for lightweight
journaling on top of softupdates(SU+J),
which greatly reduces the need for
background fsck, and uses NFS-style
ACLs by default.
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Microsoft ScanDisk
On Unix-like
systems there are
tools like
fsck_msdosfs to do
the same task.
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Fsck
The system utility 'fsck' (for 'f'ile
's'ystem 'c'hec'k') is a tool for checking
the consistency of a file system in Unix
and Unix-like operating systems, such
as Linux and Mac OS X.
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Fsck - Use
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Generally, fsck is run automatically at
boot time. There are two common
triggers for automatically executing
fsck. Either the operating system
detects that a file system is in an
inconsistent state (likely due to a nongraceful shutdown such as a Crash
(computing)|crash or power loss), or
after a certain number of times that
the file system is mounted (to prevent
small, undetected inconsistencies
from becoming exacerbated).
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Fsck - Use
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The fsck command works directly on datastructures that are internal, and intrinsically
specific to a file system implementation. A
matching fsck command that is tailored
specifically to the design of the file system is
often provided by the authors of a file system.
The exact behaviors of various fsck
implementations vary, but they typically follow
a common order of internal operations and
provide a common command-line interface to
the user.
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Fsck - Use
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Most fsck utilities provide options for either
interactively repairing damaged file
systems (the user must decide how to fix
specific problems), automatically deciding
how to fix specific problems (so the user
does not have to answer any questions),
or reviewing the problems that need to be
resolved on a file system without actually
fixing them
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Fsck - Use
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A journaling file system is designed such
that tools such as fsck do not need to be
run after unclean shutdown (i.e
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Fsck - Use
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While fsck usually only checks metadata,
such as the journal log, but never checks
the data itself, scrub checks everything,
including metadata and the data
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Fsck - Use as profanity
Because of the severity of fsck not
being able to resolve this error, the
terms fsck and fscked have come into
use among Unix system administrators
as a minced oath.
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Fsck - Use as profanity
A report from a question and answer
session at USENIX 1998 claims that fsck
originally had a different name.
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Fsck - Use as profanity
:Dennis Ritchie: Well, the second letter
was
differenthttps://groups.google.com/forum/#
!msg/alt.sysadmin.recovery/tsGbbkvHo2c/
6TPj9d3A6wJhttp://www.c2.com/cgi/wiki?Min
dFsck
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Fsck - Use as profanity
Another online use of the term, not
really profanity but a curt way of
dismissing someone, was Go fsck
yourself, meaning to go and correct
your issue (attitude, ignorance of the
subject matter, etc.) before posting
again. This takes the fsck process as a
metaphor, since running fsck involves
rebooting and fixing fundamental
errors on the hard drive before
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Expect
It is used to automate control of
interactive application
software|applications such as telnet,
ftp, Passwd (command)|passwd, fsck,
rlogin, tip (unix utility)|tip, Secure
Shell|ssh, and others
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Fuck - Common alternatives
Huff Jr., Re: Mandrake 8.2 Musings,
alt.os.linux.mandrake,
[http://groups.google.com/group/alt.os.linux.m
andrake/msg/3641a310fcc6ed93?dmode=so
urce Google Groups] At some point in your
Linux career you should ask yourself: 'If there
are 3.4million successful, happy Mandrake
users...what the 'fsck' is wrong with me?' In
Battlestar Galactica the bowdlerized form
'Frak (expletive)|Frack' (spelt 'Frak
(expletive)|Frak' in the Battlestar Galactica
(reimagining)|reimagined 2003 version) was
used as a substitute for fuck
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List of DOS commands - CHKDSK
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Equivalent to the Unix
command fsck
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AdvFS
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The original team had enough confidence
in its log based recovery to release it
without an fsck style recovery utility on the
assumption that the file system journal
would always be allocated on mirrored
drives.
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EncFS - Advantages
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* Corruption of data is more isolated.
Data corruption of filedata is local to a
single file and data corruption of the
filesystem can be corrected with a
reliable filesystem repair utility like
fsck. In some whole-disk encryption
systems, one or both of these
attributes are not present.
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F2FS - Implemented
* Offline Fsck|filesystem check
(Check and fix
inconsistency[https://lkml.org/lkml/
2014/9/20/104 f2fs-tools: release 1.4.0]
by Jaegeuk Kim)
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DRBD - Mode of operation
This transition may require a
subsequent verification of the
integrity of the file system stacked on
top of DRBD, by way of a
fsck|filesystem check or a journaling
filesystem|journal replay
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HFS Plus - Linux
The Linux kernel includes the hfsplus
module[http://git.kernel.org/?p=linux/kernel
/git/torvalds/linux2.6.git;a=tree;f=fs/hfsplus;hb=HEAD Git
Repository Kernel.org] for mounting HFS+
filesystems read-write. HFS+ fsck and
mkfs have been ported to Linux and are
part of the hfsprogs
package.[http://packages.debian.org/sid/hf
sprogs User-space supporting tools for
HFS+ filesystems under Posix systems.]
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BBC Redux - Technical details
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The fsck-free ZFS file system is used
after experiments with Unix File System
(UFS) proved it to be too slow
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CHKDSK
'CHKDSK' (short for check disk) is a
system software|system tool in DOS, OS/2
and Windows. It verifies the file system
integrity of a Volume (computing)|volume
and fixes logical file system errors. It is
similar to the fsck command in Unix.
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