fbackup(1M) fbackup(1M)
NAME [Toc] [Back]
fbackup - selectively back up files
SYNOPSIS [Toc] [Back]
/usr/sbin/fbackup -f device [-f device] ... [-0-9] [-nsuvyAEl]
[-i path] [-e path] [-g graph] [-d path] [-I path] [-V path]
[-c config]
/usr/sbin/fbackup -f device [-f device] ... [-R restart] [-nsuvyAEl]
[-d path] [-I path] [-V path] [-c config]
DESCRIPTION [Toc] [Back]
fbackup combines features of dump and ftio to provide a flexible,
high-speed file system backup mechanism (see dump(1M) and ftio(1)).
fbackup selectively transfers files to an output device. For each
file transferred, the file's contents and all the relevant information
necessary to restore it to an equivalent state are copied to the
output device. The output device can be a raw magnetic tape drive
(for example, a DLT tape drive), the standard output, a rewritable
magneto-optical disk, or a file.
The selection of files to back up is done by explicitly specifying
trees of files to be included or excluded from an fbackup session.
The user can construct an arbitrary graph of files by using the -i or
-e options on the command line, or by using the -g option with a graph
file. For backups being done on a regular basis, the -g option
provides an easier interface for controlling the backup graph.
fbackup selects files in this graph, and attempts to transfer them to
the output device. The selectivity depends on the mode (full or
incremental) in which fbackup is being used.
When doing full backups, all files in the graph are selected. When
doing incremental backups, only files in the graph that have been
modified since a previous backup of that graph are selected. If an
incremental backup is being done at level 4 and the -g option is used,
the database file is searched for the most recent previous backup at
levels 0-3. If a file's modification time is before the time when the
last appropriate session began and the i-node change time is before
the time that same session ended, the file is not backed up. All
directories lying on the path to a file that qualifies for the
incremental backup will also be on the backup media, even if the
directories do not qualify on their own status.
If fbackup is used for incremental backups, a database of past backups
must be kept. fbackup maintains this data in the text file
/var/adm/fbackupfiles/dates, by default. Note that the directory
/var/adm/fbackupfiles must be created prior to the first time fbackup
is used for incremental backups. The -d option can be used to specify
an alternate database file. The user can specify to update this file
when an fbackup session completes successfully. Entries for each
session are recorded on separate pairs of lines. The following four
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items appear on the first line of each pair: the graph file name,
backup level, starting time, and ending time (both in time(2) format).
The second line of each pair contains the same two times, but in
strftime(3C) format. These lines contain the local equivalent of
STARTED:, the start time, the local equivalent of ENDED:, and the
ending time. These second lines serve only to make the dates file
more readable; fbackup does not use them. All fields are separated by
white space. Graph file names are compared character-by-character
when checking the previous-backup database file to ascertain when a
previous session was run for that graph. Caution must be exercised to
ensure that, for example, graph and ./graph are not used to specify
the same graph file because fbackup treats them as two different graph
files.
The general structure of an fbackup volume is the same, no matter what
type of device is used. There are some small specific differences due
to differing capabilities of devices. The general structure is as
follows:
+ reserved space for ASCII tape label (1024 bytes)
+ fbackup volume header (2048 bytes)
+ session index (size in field of volume header)
+ data
Each file entry in the index contains the file size, the volume number
and the pathname of the file. At the beginning of every volume,
fbackup assumes that all files not already backed up will fit on that
volume, an erroneous assumption for all but the last volume. Indices
are accurate only for the previous volumes in the same set. Hence,
the index on the last volume may indicate that a file resides on that
volume, but it may not have actually been backed up (for example, if
it was removed after the index was created, but before fbackup
attempted to back it up). The only index guaranteed to be correct in
all cases is the on-line index (-I option), which is produced after
the last volume has been written.
Specific differences in the structure of fbackup volumes are listed
below:
+ When using magnetic tape devices, the main blocks of
information (tape label, volume header, index, data) are
separated by EOF marks. fbackup also checkpoints the media
periodically to enhance error recovery. If a write error is
detected, the user normally has two options: (1) a new volume
can be mounted and that volume rewritten from the beginning;
or, (2) if the volume is not too severely damaged, the good
data before the error can be saved, and the write error is
treated as a normal end-of-media condition. The blocks of
data with their checkpoint records are also separated by EOF
marks. In addition, for DDS tape drives, if fast search marks
are supported, these will be used to enhance selective
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recovery speed by placing them between blocks of files.
Similarly on DLT tape drives, faster selective recovery is
achieved using the EOF marks used for checkpointing in
conjunction with the file sizes given in the index.
+ For a magneto-optical device, a disk, a file, or standard
output, there are no special marks separating the information
pieces; the backup is always a single file (volume).
fbackup provides the ability to use UCB-mode tape drives. This makes
it possible to overlap the tape rewind times if two or more tape
drives are connected to the system.
Set-up [Toc] [Back]
There are several things the user will want to consider when setting
up fbackup for regular use. These include type of device and media,
full versus incremental frequency, amount of logging information to
keep on-line, structure of the graph file, and on-line versus off-line
backup.
The type of device used for backups can affect such things as media
expenses, ability to do unattended backups, and speed of the backup.
Using 36-track tapes will probably result in the highest performance,
but require user intervention for changing tapes. Both DLT and DDS
autochangers and libraries can provide unattended backups. A
magneto-optical autochanger can also provide an unattended backup for
a large system and long life media, however the media cost is high.
Lower cost and good performance can be achieved with a single DLT tape
drive, but multi-volume backups must be attended.
It is also important to consider how often full backups should be
made, and how many incremental backups to make between full backups.
Time periods can be used, such as a full backup every Friday and
incrementals on all other days. Media capacities can be used if
incremental backups need to run unattended. The availability of
personnel to change media can also be an important factor as well as
the length of time needed for the backup. Other factors may affect
the need for full and incremental backup combinations such as
contractual or legal requirements.
If backup information (output from the -V or -I options) is kept online,
the required storage space must also be considered. Index file
sizes are hard to predict in advance because they depend on system
configuration. Each volume header file takes less than 1536 bytes.
Of course the more information that is kept on-line, the faster
locating a backup media for a recovery will be.
There are several ways to structure the graph file or files used in a
system backup. The first decision involves whether to use one or more
than one graph file for the backup. Using one file is simpler, but
less flexible. Using two or more graph files simplifies splitting
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backups into logical sets. For example, one graph file can be used
for system disks where changes tend to be less frequent, and another
graph file for the users area. Thus two different policies can be
implemented for full and incremental backups.
fbackup was designed to allow backups while the system is in use by
providing the capability to retry an active file. When absolute
consistency on a full backup is important, the system should probably
be in single-user mode. However, incremental backups can be made
while the system is in normal use, thus improving system up-time.
Options [Toc] [Back]
-c config config is the name of the configuration file, and can
contain values for the following parameters:
+ Number of 1024-byte blocks per record.
+ Number of records of shared memory to allocate.
+ Number of records between checkpoints. Since the
EOF marks between checkpoints are also used for
fast searching on DLT tape drives, changing the
checkpoint frequency may also affect selective
recovery speed (see WARNINGS section).
+ Number of file-reader processes.
+ Maximum number of times fbackup is to retry an
active file.
+ Maximum number of bytes of media to use while
retrying the backup of an active file.
+ Maximum number of times a magnetic tape volume
can be used.
+ Name of a file to be executed when a volume
change occurs. This file must exist and be
executable.
+ Name of a file to be executed when a fatal error
occurs. This file must exist and be executable.
+ The number of files between the fast search marks
on DDS tapes. The cost of these marks are
negligible in terms of space on the DDS tape.
Not all DDS tape devices support fast search
marks.
Each entry in the configuration file consists of one
line of text in the following format: identifier, white
space, argument. In the following sample configuration
file, the number of blocks per record is set to 16; the
number of shared memory records is set to 16; the
checkpoint frequency is set to 256; the number of file
reader processes is set to 2; the maximum number of
retries of an active file is set to 5; the maximum
retry space for active files is set to 5,000,000 bytes;
the maximum number of times a magnetic tape volume can
be used is set to 100; the file to be executed at
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volume change time is /var/adm/fbackupfiles/chgvol; the
file to be executed when a fatal error occurs is
/var/adm/fbackupfiles/error; and the number of files
between fast search marks on DDS tapes is set to 200.
blocksperrecord 16
records 16
checkpointfreq 256
readerprocesses 2 (maximum of 6)
maxretries 5
retrylimit 5000000
maxvoluses 100
chgvol /var/adm/fbackupfiles/chgvol
error /var/adm/fbackupfiles/error
filesperfsm 200
Each value listed is also the default value, except
chgvol and error, which default to null values.
-d path This specifies a path to a database for use with
incremental backups. It overrides the default database
file /var/adm/fbackupfiles/dates.
-e path path specifies a tree to be excluded from the backup
graph. This tree must be a subtree of part of the
backup graph. Otherwise, specifying it will not
exclude any files from the graph. There is no limit on
how many times the -e option can be specified.
-f device device specifies the name of an output file. If the
name of the file is -, fbackup writes to the standard
output. There is no default output file; at least one
must be specified. If more than one output file is
specified, fbackup uses each one successively and then
repeats in a cyclical pattern. Patterns can be used in
the device name in a manner resembling file name
expansion as done by the shell (see sh(1) and other
shell manual entries). The patterns must be protected
from expansion by the shell by quoting them. The
expansion of the pattern results in all matching names
being in the list of devices used.
There is slightly different behavior if remote devices
are used. A device on the remote machine can be
specified in the form machine:device. fbackup creates
a server process from /usr/sbin/rmt on the remote
machine to access the tape device. If /usr/sbin/rmt
does not exist on the remote system, fbackup creates a
server process from /etc/rmt on the remote machine to
access the tape device. Only magnetic tapes can be
remote devices. When remote DDS tape devices are used,
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the fast search marks capability is not used.
-g graph graph defines the graph file. The graph file is a text
file containing the list of file names of trees to be
included or excluded from the backup graph. These
trees are interpreted in the same manner as when they
are specified with the -i and -e options. Graph file
entries consist of a line beginning with either i or e,
followed by white space, and then the path name of a
tree. Lines not beginning with i or e are treated as
an error. There is no default graph file. For
example, to back up all of /usr except for the subtree
/usr/lib, a file could be created with the following
two records:
i /usr
e /usr/lib
-i path path specifies a tree to be included in the backup
graph. There is no limit on how many times the -i
option can be specified.
-n Cross NFS mount points. By default, fbackup does not
cross NFS mount points, regardless of paths specified
by the -i or -g options.
-l Includes LOFS files specified by the backup graph. By
default, fbackup does not cross LOFS mount points. If
-l is specified, and the backup graph includes files
which are also in an LOFS directory that is in the
backup graph, then those files will be backed up twice.
-s Back up the object that a symbolic link refers to. The
default behavior is to back up the symbolic link.
-u Update the database of past backups so that it contains
the backup level, the time of the beginning and end of
the session, and the graph file used for this fbackup
session. For this update to take place, the following
conditions must exist: Neither the -i nor the -e option
can be used; the -g option must be specified exactly
once (see below); the fbackup must complete
successfully.
-v Run in verbose mode. Generates status messages that
are otherwise not seen.
-y Automatically answer yes to any inquiries.
-A Do not back up optional entries of access control lists
(ACLs) for files. Normally, all mode information is
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backed up including the optional ACL entries. With the
-A option, the summary mode information (as returned by
stat()) is backed up. Use this option when backing up
files from a system that contains ACLs to be recovered
on a system that does not understand ACLs (see acl(5)).
-E Do not back up extent attributes. Normally, all extent
attributes that have been set are included with the
file. This option only applies to file systems which
support extent attributes.
-I path path specifies the name of the on-line index file to be
generated. It consists of one line for each file
backed up during the session. Each line contains the
file size, the volume number on which that file
resides, and the file name. If the -I option is
omitted, no index file is generated.
-V path The volume header information is written to path at the
end of a successful fbackup session. The following
fields from the header are written in the format
label:value with one pair per line.
Magic Field On a valid fbackup media it
contains the value FBACKUP_LABEL
(HP-UX release 10.20 and
beyond). Before HP-UX release
10.20, it contained the value
FBACKUP LABEL.
Machine Identification This field contains the result
of uname -m.
System Identification This field contains the result
of uname -s.
Release Identification This field contains the result
of uname -r.
Node Identification This field contains the result
of uname -n.
User Identification This field contains the result
of cuserid() (see cuserid(3S)).
Record Size This field contains the maximum
length in bytes of a data
record.
Time This field contains the clock
time when fbackup was started.
Media Use This field contains the number
of times the media has been used
for backup. Since the
information is actually on the
media, this field will always
contain the value 0.
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Volume Number This field contains a #
character followed by 3 digits,
and identifies the number of
volumes in the backup.
Checkpoint Frequency This field contains the number
of data records between
checkpoints.
Index Size This field contains the size of
the index.
Backup Identification Tag
This field is composed of two
items: the process ID (pid) and
the start time of that process.
Language This field contains the language
used to make the backup.
-R restart Restart an fbackup session from where it was previously
interrupted. The restart file contains all the
information necessary to restart the interrupted
session. None of the -[ieg0-9] options can be used
together with the restart option.
-0-9 This single-digit number is the backup level. Level 0
indicates a full backup. Higher levels are generally
used to perform incremental backups. When doing an
incremental backup of a particular graph at a
particular level, the database of past backups is
searched to find the date of the most recent backup of
the same graph that was done at a lower level. If no
such entry is found, the beginning of time is assumed.
All files in the graph that have been modified since
this date are backed up.
Access Control Lists (ACLs) [Toc] [Back]
If a file has optional ACL entries, the -A option is required to
enable its recovery on a system where the ACL capability is not
present.
EXTERNAL INFLUENCES [Toc] [Back]
Environment Variables
LC_COLLATE determines the order in which files are stored on the
backup device and the order of output by the -I option.
LC_TIME determines the format and contents of date and time strings.
LC_MESSAGES determines the language in which messages are displayed.
If LC_COLLATE, LC_TIME, and LC_MESSAGES are not all specified in the
environment, or if either is set to the empty string, the value of
LANG is used as a default for each unspecified or empty variable. If
LANG is not specified or is set to the empty string, a default of "C"
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(see lang(5)) is used instead of LANG. If any internationalization
variable contains an invalid setting, fbackup behaves as if all
internationalization variables are set to "C". See environ(5).
International Code Set Support [Toc] [Back]
Single- and multi-byte character code sets are supported.
RETURN VALUE [Toc] [Back]
fbackup returns one of the following values:
0 upon normal completion.
1 if it is interrupted but allowed to save its state for possible
restart.
2 if any error conditions prevent the session from completing.
4 if any warning conditions are encountered.
If warnings occur, the operator should check the fbackup logs to
verify the sanity of the backup.
EXAMPLES [Toc] [Back]
In the following two examples, assume the graph of interest specifies
all of /usr except /usr/lib (as described for the -g option above).
The first example is a simple case where a full backup is done but the
database file is not updated. This can be invoked as follows:
/usr/sbin/fbackup -0i /usr -e /usr/lib -f /dev/rmt/c0t0d0BEST
The second example is more complicated, and assumes the user wants to
maintain a database of past fbackup sessions so that incremental
backups are possible.
If sufficient on-line storage is available, it may be desirable to
keep several of the most recent index files on disk. This eliminates
the need to recover the index from the backup media to determine if
the files to be recovered are on that set. One method of maintaining
on-line index files is outlined below. The system administrator must
do the following once before fbackup is run for the first time
(creating intermediate level directories where necessary):
+ Create a suitable configuration file called config in the
directory /var/adm/fbackupfiles.
+ Create a graph file called usr-usrlib in the directory
/var/adm/fbackupfiles/graphs.
+ Create a directory called usr-usrlib in the directory
/var/adm/fbackupfiles/indices.
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A shell script that performs the following tasks could be run for each
fbackup session:
+ Build an index file path name based on both the graph file
used (passed as a parameter to the script) and the start time
of the session (obtained from the system). For example:
/var/adm/fbackupfiles/indices/usr-usrlib/871128.15:17
(for Nov 28, 1987 at 3:17 PM)
+ Invoke fbackup with this path name as its index file name.
For example:
cd /var/adm/fbackupfiles
/usr/sbin/fbackup -0uc config -g graphs/usr-usrlib\
-I indices/usr-usrlib/871128.15:17\
-f /dev/rmt/c0t0d0BEST
When the session completes successfully, the index is automatically
placed in the proper location.
WARNINGS [Toc] [Back]
fbackup consists of multiple executable objects, all of which are
expected to reside in directory /usr/sbin.
fbackup does not require special privileges. However, if the user
does not have access to a given file, the file is not backed up.
For security reasons, configuration files and the chgvol and error
executable files should only be writable by their owners.
With release 10.20, HP-UX supports large files (greater than 2GB) and
increased UID/GIDs (greater than 60,000). Archives containing files
with these attributes would cause severe problems on systems that do
not support the increased sizes. For this reason, fbackup creates
tapes with a new magic number ("FBACKUP_LABEL"). This prevents
fbackup tape archives from being restored on pre-10.20 HP-UX systems.
frecover still reads both tape formats so that fbackup tape archives
created on pre-10.20 HP-UX systems can be restored.
EOF marks are used for checkpointing on all magnetic tape devices. On
DLT tape devices, these EOF marks are also used for fast searching on
a selective recovery; "fast searching" in this case means spacing to
the nearest checkpoint before the desired file, and then reading until
the file is found. With this dual purpose for checkpoints, caution
should be used when changing the checkpoint frequency parameter.
Starting with HP-UX Release 8.0, fbackup does not back up network
special files because RFA networking is obsolete. A warning message
is issued if a network special file is encountered in the backup graph
and the file is skipped.
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The use of fbackup for backing up NFS mounted file systems is not
guaranteed to work as expected if the backup is done as a privileged
user. This is due to the manner in which NFS handles privileged-user
access by mapping user root and uid 0 to user nobody, usually uid -2,
thus disallowing root privileges on the remote system to a root user
on the local system.
The utility set comprised of fbackup and frecover was originally
designed for use on systems equipped with not more than one gigabyte
of total file system storage. Although the utilities have no
programming limitations that restrict users to this size, complete
backups and recoveries of substantially larger systems can cause a
large amount of system activity due to the amount of virtual memory
(swap space) used to store the indices. Users who want to use these
utilities, but are noticing poor system-wide performance due to the
size of the backup, are encouraged to back up their systems in
multiple smaller sessions, rather than attempting to back up the
entire system at one time.
Due to present file-system limitations, files whose inode data, but
not their contents, are modified while a backup is in progress might
be omitted from the next incremental backup of the same graph. Also,
fbackup does not reset the inode change times of files to their
original values.
fbackup should not be used with no-rewind devices, for example,
/dev/rmt/0mn.
fbackup allocates resources that are not returned to the system if it
is killed in an ungraceful manner. If it is necessary to kill
fbackup, send it a SIGTERM, not a SIGKILL.
If sparse files are backed up without using data compression, a very
large amount of media can be consumed.
fbackup creates volumes with a format that makes duplication of
volumes by dd impossible (see dd(1)). Copying an fbackup volume
created on one media type to another media type does not produce a
valid fbackup volume on the new media because the formats of volumes
on raw magnetic tape, on a regular file, and on rewritable optical
disks are not identical.
When configuring the parameter blocksperrecord (see -c option), the
record size is limited by the maximum allowed for the tape drive.
Common record sizes include 128 blocks for DLT and DDS tape drives,
and 60 blocks for the HP7980. Note also that the blocksize used in
earlier releases (7.0 and before) was 512 bytes, whereas it is now
1024 bytes. This means that the same value specified in
blocksperrecord in an earlier release creates blocks twice their
earlier size in the current release; for example, a blocksperrecord
parameter of 32 would create 16-Kbyte blocks at Release 7.0, but now
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creates 32-Kbyte blocks. If blocksperrecord exceeds the byte count
allowed by the tape drive, the tape drive rejects the write, causing
an error to be communicated to fbackup which fbackup interprets as a
bad tape. The resulting write error message resembles the following:
fbackup (3013): Write error while writing backup at tape block 0.
Diagnostic error from tape 11...... SW_PROBLEM (printed by driver on console)
fbackup (3102): Attempting to make this volume salvageable.
etc.
DEPENDENCIES [Toc] [Back]
NFS
Access control lists of networked files are summarized (as returned in
st_mode by stat()), but not copied to the new file (see stat(2)).
fbackup does not support QIC-120 and QIC-150 formats on QIC devices.
If fbackup is attempted for these formats, fbackup fails and the
following message is displayed :
mt lu X: Write must be a multiple of 512 bytes in QIC 120 or QIC
150
AUTHOR [Toc] [Back]
fbackup was developed by HP.
FILES [Toc] [Back]
/var/adm/fbackupfiles/dates database of past backups
SEE ALSO [Toc] [Back]
cpio(1), ftio(1), dump(1M), frecover(1M), restore(1M), rmt(1M),
stat(2), acl(5), mt(7).
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