fbackup(1M)

NAME

fbackup — selectively back up files

SYNOPSIS

/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]

Remarks

Note: The fbackup, frecover, and ftio commands are deprecated for creating new archives. See WARNINGS for more information.

DESCRIPTION

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 items appear on the first line of each pair: the graph file name, backup level, starting time, and ending time (both in time() format). The second line of each pair contains the same two times, but in strftime() 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 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

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 on-line, 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 2048 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 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

-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 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, 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 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 11i Version 3 and beyond). Previous values of this field were FBACKUP_LABEL (between HP-UX 10.20 and 11i Version 2 inclusive) and FBACKUP LABEL (before HP-UX 10.20).
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.
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)

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

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" (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

Single- and multi-byte character code sets are supported.

RETURN VALUE

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

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/rtape/tape4QIC150 

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.

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/rtape/tape4QIC150

When the session completes successfully, the index is automatically placed in the proper location.

WARNINGS

The fbackup, frecover, and ftio commands are deprecated for creating new archives. In a future HP-UX release, creation of new archives with these commands will not be supported. Support will be continued for archive retrieval. Use the standard pax command (portable archive interchange) to create archives. See pax(1).

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.

In HP-UX 11i Version 3, the maximum value for fields returned via uname() was increased (from 8 to 256). To accommodate the larger size, a format change was necessary. A new magic number, FBACKUP*LABEL, was created to distinguish this new format.

Likewise with HP-UX 10.20, HP-UX added support for large files (greater than 2GB) and increased UID/GIDs (greater than 60,000). The magic number associated with this release through HP-UX 11i Version 2 (inclusive) is FBACKUP_LABEL.

Archives and files with formats and attributes that are unsupported on previous HP-UX releases could cause severe problems or unpredictable behavior if attempts were made to restore onto these systems. For this reason, fbackup creates tapes with a magic number that is only recognized on releases which support the features and format being archived. This prevents fbackup tape archives from being restored on earlier HP-UX systems than are supported. frecover still reads all tape formats so that fbackup tape archives created on earlier 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.

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 or /dev/rtape/tape1_BESTn on systems where legacy Device Special Files (DSF) is disabled.

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 HP-UX 7.0, but now 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

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

fbackup was developed by HP.

FILES

/var/adm/fbackupfiles/dates: database of past backups