NAME
afio - manipulate archives and files
SYNOPSIS
... |
afio -o [ options ] archive : write (create)
archive
afio -i [ options ] archive : install (unpack)
archive
afio -t [ options ] archive : list
table-of-contents of archive
afio -r [ options ] archive : verify archive
against filesystem
afio -p [ options ] directory [ ... ] : copy
files
DESCRIPTION
Afio manipulates groups of files, copying them within the (collective) filesystem or between the filesystem and an afio archive.
With -o, reads pathnames from the standard input and writes an archive.
With -t, reads an archive and writes a table-of-contents to the standard output.
With -i, installs the contents of an archive relative to the working directory.
With -p, reads pathnames from the standard input and copies the files to each directory. Cannot be combined with the -Z option.
With -r, reads archive and verifies it against the filesystem. This is useful for verifying tape archives, to ensure they have no bit errors. The verification compares file contents, but not permission bits and non-file filesystem entities, so it cannot be used as a reliable tool to detect every possible change made to a filesystem.
Creates missing directories as necessary, with permissions to match their parents.
Removes leading slashes from pathnames, making all paths relative to the current directory. This is a safety feature to prevent inadvertent overwriting of system files when doing restores. To suppress this safety feature, the -A option must be used while writing an archive, but also when reading (installing), verifying, and cataloging an existing archive.
Supports compression while archiving, with the -Z option. Will compress individual files in the archive, not the entire archive datastream, which makes afio compressed archives much more robust than ’tar zc’ type archives.
Supports multi-volume archives during interactive operation (i.e., when /dev/tty is accessible and SIGINT is not being ignored).
OPTIONS
|
-@ address |
Send email to address when a volume change (tape change, floppy change) is needed, and also when the entire operation is complete. Uses sendmail(1) to send the mail. | ||
|
-a |
Preserve the last access times (atimes) of the files read when making or verifying an archive. Warning: if this option is used, afio will change the last inode changed times (ctimes) of these files. Thus, this option cannot be used together with an incremental backup scheme that relies on the ctimes being preserved. | ||
|
-b size |
Read or write size-character archive blocks. Suffices of b, k, m and g denote multiples of 512, kilobytes, megabytes and gigabytes, respectively. Defaults to 5120 for compatibility with cpio(1). In some cases, notably when using ftape with some tape drives, -b 10k is needed for compatibility. Note that -b 10k is the default block size used by tar(1), so it is usually a good choice if the tape setup is known to work with tar(1). | ||
|
-c count |
Buffer count archive blocks between I/O operations. A large count is recommended for efficient use with streaming magnetic tape drives, in order to reduce the number of tape stops and restarts. | ||
|
-d |
Don’t create missing directories. | ||
|
-e bound |
Pad the archive to a multiple of bound characters. Recognizes the same suffices as -s. Defaults to 1x (the -b block size) for compatibility with cpio(1). | ||
|
-f |
Spawn a child process to actually write to the archive; provides a clumsy form of double-buffering. Requires -s for multi-volume archive support. | ||
|
-g |
Change to input file directories. Avoids quadratic filesystem behavior with long similar pathnames. Requires all absolute pathnames, including those for the -o archive and the -p directories. | ||
|
-h |
Follow symbolic links, treating them as ordinary files and directories. | ||
|
-j |
Don’t generate sparse filesystem blocks on restoring files. By default, afio creates sparse filesystem blocks (with lseek(2)) when possible when restoring files from an archive, but not if these files were stored in a compressed form. Unless stored in a compressed form, sparse files are not archived efficiently: they will take space equal to the full file length. (The sparse file handling in afio does not make much sense except in a historical way.) | ||
|
-k |
Rather than complaining about unrecognizable input, skip unreadable data (or partial file contents) at the beginning of the archive file being read, and search for the next valid archive header. This option is needed to deal with certain types of backup media damage. It is also useful to support quick selective restores from multi-volume archives, or from searchable block devices, if the volume or location of the file to be restored is known in advance (see the -B option). If, for example, a selective restore is done with the fourth volume of a multi-volume afio archive, then the -k option needs to be used, else afio will complain about the input not being a well-formed archive. | ||
|
-l |
With -o, write file contents with each hard link. |
With -t, report hard links.
With -p, attempt to link files rather than copying them.
|
-m |
Mark output files with a common current timestamp (rather than with input file modification times). | ||
|
-n |
Protect newer existing files (comparing file modification times). | ||
|
-s size |
Restrict each portion of a multi-volume archive to size characters. This option recognizes the same size suffices as -b. Also, the suffix x denotes a multiple of the -b block size (and must follow any -b specification). size can be a single size or a comma-seperated list of sizes, for example ’2m,5m,8m’, to specify different sizes for the subsequent volumes. If there are more volumes than sizes, the last specified size is used for all remaining volumes. If this option is used, the special character sequences %V and %S in the input/output filename or command string are replaced by the current volume number and volume size. Use %% to produce a single % character. The -s option is useful with finite-length devices which do not return short counts at end of media (sigh); output to magnetic tape typically falls into this category. When an archive is being read or written, using -s causes afio to prompt for the next volume if the specified volume length is reached. The -s option will also cause afio to prompt if there is a premature EOF while reading the input. The special case -s 0 will activate this prompting for the next volume on premature EOF without setting a volume length. When writing an archive, afio will prompt for the next volume on end-of-media, even without -s 0 being supplied, if the device is capable of reporting end-of-media. If the volume size specified is not a multiple of the block size set with the -b option, then afio(1) will silently round down the volume size to the nearest multiple of the block size. This rounding down can be suppressed using the -9 option: if -9 is used, afio(1) will write a small block of data, smaller than the -b size, at the end of the volume to completely fill it to the specified size. Some devices are not able to handle such small block writes. | ||
|
-u |
Report files with unseen links. | ||
|
-v |
Verbose. Report pathnames (to stderr) as they are processed. When used with -t, gives an ls -l style report (including link information) to stdout instead. When used twice (-vv) with -o, gives an ls -l style report to stdout while writing the archive. (But this use of -vv will not work if the archive is also being written to stdout.) | ||
|
-w filename |
Treats each line in filename as an -y pattern, see -y. | ||
|
-x |
Retain file ownership and setuid/setgid permissions. This is the default for the super-user; he may use -X to override it. | ||
|
-y pattern |
Restrict processing of files to names matching shell wildcard pattern pattern. Use this flag once for each pattern to be recognized. With the possible exception of the presence of a leading slash, the complete file name as appearing in the archive table-of-contents must match the pattern, for example the file name ’etc/passwd’ is matched by the pattern ’*passwd’ but NOT by the pattern ’passwd’. See ’man 7 glob’ for more information on shell wildcard pattern matching. The only difference with shell wildcard pattern matching is that in afio the wildcards will also match ’/’ characters in file names. For example the pattern ’/usr/src/*’ will match the file name ’/usr/src/linux/Makefile’, and any other file name starting with ’/usr/src’. Unless the -S option is given, any leading slash in the pattern or the filename is ignored when matching, e.g. /etc/passwd will match etc/passwd. Use -Y to supply patterns which are not to be processed. -Y overrides -y if a filename matches both. See also -w and -W. See also the -7 option, which can be used to modify the meaning of -y, -Y, -w, and -W when literal matching without wildcard processing is needed. Note: if afio was compiled without using the GNU fnmatch library, then the full shell wildcard pattern syntax cannot be used, and matching support is limited to patterns which are a full literal file name and patterns which end in ’*’. | ||
|
-z |
Print execution statistics. This is meant for human consumption; use by other programs is officially discouraged. | ||
|
-A |
Do not turn absolute paths into relative paths. That is don’t remove the leading slash. Applies to the path names written in an archive, but also to the path names read out of an archive during read (install), verify, and cataloging operations. | ||
|
-B |
If the -v option is used, prints the byte offset of the start of each file in the archive. If your tape drive can start reading at any position in an archive, the output of -B can be useful for doing quick selective restores. |
-D controlscript
Set the control script name to controlscript, see the section on control files below.
-E [+]filename | -E CS | -E CI
While creating an archive with compressed files using the -Z option, disable (attempts at) compression for files with particular extensions. This option can be used to speed up the creation of the archive, by making afio avoid trying to use gzip on files that contain compressed data already. By default, if no specific -E option is given, all files with the extensions .Z .z .gz .bz2 .tgz .arc .zip .rar .lzh .lha .uc2 .tpz .taz .tgz .rpm .zoo .deb .gif .jpeg .jpg .tif .tiff .png .pdf .arj .avi .bgb .cab .cpn .hqx .jar .mp3 .mpg .mpq .pic .pkz .psn .sit .ogg and .smk will not be compressed. Also by default, the file extension matching is case-insensitive (to do the right thing with respect to MS-DOS based filesystems). The -E filename form of this option will replace the default list of file extensions by reading a new list of file extensions, separated by whitespace, from filename. filename may contain comments preceded by a #. The extensions in filename should usually all start with a dot, but they do not need to start with a dot, for example the extension ’tz’ will match the file name ’hertz’. The -E +filename form (with a + sign in front of filename) can be used to specify extensions in addition to the built-in default list, instead of replacing the whole default list. To make extension matching case-sensitive, add the special option form -E CS to the command line. The form -E CI invokes the (default) case-insensitive comparison. See also the -6 option, which offers an additional way to suppress compression.
|
-F |
This is a floppy disk, -s is required. Causes floppy writing in O_SYNC mode under Linux. With kernel version 1.1.54 and above, this allows afio to detect some floppy errors while writing. Uses shared memory if compiled in otherwise mallocs as needed (a 3b1 will not be able to malloc the needed memory w/o shared memory), afio assumes either way you can malloc/shmalloc a chunk of memory the size of one disk. Examples: 795k: 3.5" (720k drive), 316k (360k drive) |
At the end of each disk this
message occurs:
Ready for disk [#] on [output]
(remove the disk when the light goes out)
Type "go" (or "GO") when ready to
proceed
(or "quit" to abort):
|
-G factor |
Specifies the gzip(1) compression speed factor, used when compressing files with the -Z option. Factor 1 is the fastest with least compression, 9 is slowest with best compression. The default value is 6. See also the gzip(1) manual page. If you have a slow machine or a fast backup medium, you may want to specify a low value for factor to speed up the backup. On large (>200k) files, -G 1 typically zips twice as fast as -G 6, while still achieving a better result than compress(1). The zip speed for small files is mainly determined by the invocation time of gzip (1), see the -T option. |
-H promptscript
Specify a script to run, in stead of using the normal prompt, before advancing to the next archive volume. The script will be run with the volume number, archive specification, and the reason for changing to the next volume as arguments. The script should exit with 0 for OK and 1 for abort, other exit codes will be treated as fatal errors. As of afio version 2.5.2, the promptscript can be a file name containing spaces or other special characters.
|
-J |
Try to continue after a media write error when doing a backup (normal behavior is to abort with a fatal error). | ||
|
-K |
Verify the output against what is in the memory copy of the disk (-F required). If the writing or verifying fails the following menu pops up |
[Writing/Verify] of disk [disk #] has FAILED!
|
Enter 1 to RETRY this disk | |
|
Enter 2 to REFORMAT this disk before a RETRY | |
|
Enter quit to ABORT this backup |
Currently, afio will not process the answers 1 and 2 in the right way. The menu above is only useful in that it signifies that something is wrong.
-L Log_file_path
Specify the name of the file to log errors and the final totals to.
|
-M size |
Specifies the maximum amount of memory to use for the temporary storage of compression results when using the -Z option. The default is -M 250m (250 megabytes). If the compressed version of a file is larger than this (or if afio runs out of virtual memory), gzip(1) is run twice of the file, the first time to determine the length of the result, the second time to get the compressed data itself. | ||
|
-P progname |
Use the program progname instead of the standard gzip(1) for compression and decompression with the -Z option. For example, use the options -Z -P bzip2 to write and install archives using bzip2(1) compression. If progname does not have command line options (-c, -d, and -<number>) in the style of gzip(1) then the -Q option can be used to supply the right options. The compression program used must have the property that, if the output file size exceeds the value of the -M option, then when the compression program is run for a second time on the same input, it must produce an output with exactly the same size. (See also the -M option description.) The GnuPG (gpg) encryption program does not satisfy this lenght-preserving criterion unless its built-in compression is disabled (see examples in the afio source script3/ directory). See also the -Q, -U and -3 options. | ||
|
-Q opt |
Pass the option opt to the compression or decompression program used with the -Z option. For passing multiple options, use -Q multiple times. If no -Q flag is present, the standard options are passed. The standard options are -c -6 when the program is called for compression and -c -d when the program is called for decompression. Use the special case -Q "" if no options at all are to be passed to the program. |
-R Disk format command string
This is the command that is run when you enter 2 to reformat the disk after a failed verify. The default (fdformat /dev/fd0H1440) can be changed to a given system’s default by editing the Makefile. You are also prompted for formatting whenever a disk change is requested.
|
-S |
Do not ignore a leading slash in the pattern or the file name when matching -y and -Y patterns. See also -A. | ||
|
-T threshold |
Only compress a file when using the -Z option if its length is at least threshold. The default is -T 0k. This is useful if you have a slow machine or a fast backup medium. Specifying -T 3k typically halves the number of invocations of gzip(1), saving some 30% computation time, while creating an archive that is only 5% longer. The combination -T 8k -G 1 typically saves 70% computation time and gives a 20% size increase. The latter combination may be a good alternative to not using -Z at all. These figures of course depend heavily on the kind of files in the archive and the processor - i/o speed ratio on your machine. See also the -2 option. | ||
|
-U |
If used with the -Z option, forces compressed versions to be stored of all files, even if the compressed versions are bigger than the original versions, and disregarding any (default) values of the -T and -2 options. This is useful when the -P and -Q options are used to replace the compression program gzip with an encryption program in order to make an archive with encrypted files. Due to internal limitations of afio, use of this flag forces the writing of file content with each hard linked file, rather than only once for every set of hard linked files. WARNING: use of the -U option will also cause compression (or whatever operation the -P option indicates) on files larger than 2 GB, if these are present in the input. Not all compression programs might handle such huge files correctly (recent Linux versions of gzip, bzip2, and gpg have all been tested and seem to work OK). If your setup is obscure, some testing might be warranted. | ||
|
-W filename |
Treats each line in filename as an -Y pattern, see -Y. | ||
|
-Y pattern |
Do not process files whose names match shell wildcard pattern pattern. See also -y and -W. | ||
|
-Z |
Compress the files that go into the archive when creating an archive, or uncompress them again when installing an archive. afio -Z will compress each file in the archive individually, while keeping the archive headers uncompressed. Compared to tar zc style archives, afio -Z archives are therefore much more fault-tolerant against read errors on the backup medium. When creating an archive with the -Z option, afio will run gzip on each file encountered, and, if the result is smaller than the original, store the compressed version of the file. Requires gzip(1) to be in your path. Mainly to speed up afio operation, compression is not attempted on a file if: 1) the file is very small (see the -T option), 2) the file is very large (see the -2 option), 3) the file has a certain extension, so it probably contains compressed data already (see the -E option), 4) the file pathname matches a certain pattern, as set by the -6 option, 5) the file has hard links (this due to an internal limitation of afio, but this limitation does not apply if the -l option is also used). Regardless of the above, if the -U option is used then the compression program is always run, and the compressed result is always stored. When installing an archive with compressed files, the -Z option needs to be used in order to make afio automatically uncompress the files that it compressed earlier. The -P option can be used to do the (un)compression with programs other than gzip, see the -P (and -Q and -3) options in this manpage for details. See also the -G option which provides yet another way to tune the compression process. | ||
|
-0 |
Use filenames terminated with ’\0’ instead of ’\n’. When used as follows: find ... -print0 | afio -o -0 ..., it ensures that any input filename can be handled, even a file name containing newlines. When used as afio -t -0 ... | ..., this allows the table of contents output to be parsed unambiguosly even if the filenames contain newlines. The -0 option also affects the parsing of the files supplied by -w file and -W file options: if the option -0 precedes them in the command line then the pattern lines contained in the files should be terminated with ’\0’ in stead of ’\n’. A second use of -0 toggles the option. This can be useful when using multiple pattern files or when combining with the -t option. |
-1 warnings-to-ignore
Control if afio(1) should exit with a nonzero code after printing certain warning messages, and if certain warning messages should be printed at all. This option is sometimes useful when calling afio(1) from inside a backup script or program. afio(1) will exit with a nonzero code on encountering various ’hard’ errors, and also (with the default value of the -1 option) when it has printed certain warning messages during execution. warnings-to-ignore is a list of letters which determines the behavior related to warning messages. The default value for this option is -1 mc. For afio versions 2.4.3 and earlier, the default was -1 a. For afio versions 2.4.4 and 2.4.5, the default was -1 ’’. The defined warnings-to-ignore letters are as follows. a is for for ignoring all possible warnings on exit: if this letter is used, the printing of a warning message will never cause a nonzero exit code. m is for ignoring in the exit code any warning about missing files, which will be printed when, on creating an archive, a file whose name was read from the standard input is not found. c is for ignoring in the exit code the warning that the archive being created will not be not fully compatible with cpio or afio versions 2.4.7 or lower. C is the same as c, but in addition the warning message will not even be printed. M will suppress the printing of all warning messages asssociated with Multivolume archive handling, messages like "Output limit reached" and "Continuing". d is for ignoring in the exit code any warnings about changed files, which will be printed when, on creating an archive, a file that is being archived changes while it is being written into the archive, where the changing is detected by examining the file modification time stamp. r is for ignoring certain warnings during the verify (-r) operation. If this letter is used, some verification errors that are very probably due to changes in the filesystem, during or after the backup was made, are ignored in determining the exit code. The two verification errors that are ignored are: 1) a file in the archive is no longer present on the filesystem, and 2) the file contents in the archive and on the filesystem are different, but the file lengths or the file modification times are also different, so the difference in contents is probably due to the file on the file system having been changed. s is for ignoring in the exit code the warning printed when the protection code (as described in the section about the -8 option) rewrites a suspicious path name for a file or symlink that is being unpacked. l is for ignoring in the exit code the warning printed when the -8 nosymlinks option is used and a symlink is encountered. n is for ignoring in the exit code a particular class of no-such-file warnings: it ignores these warnings when they happen after the file has already been successfully opened. This unusual warning situation can occur when archiving files on Windows smbfs filesystems -- due to a Windows problem, smbfs files with non-ASCII characters in their names can sometimes be opened but not read. When the -Z option is used, the n letter function is (currently) only implemented for files with sizes smaller than indicated by the -T option, so in that case the -T option is also needed for this letter to have any effect.
-2 maximum-file-size-to-compress
Do not compress any files which are larger than this size when making a compressed archive with the -Z option. The default value is -2 200m (200 Megabytes). This maximum size cutoff lowers the risk that a major portion of a large file will be irrecoverable due to small media errors. If a media error occurs while reading a file that afio has stored in a compressed form, then afio and gzip will not be able to restore the entire remainder of that file. This is usually an acceptable risk for small files. However for very large files the risk of loosing a large amount of data because of this effect will usually be too big. The special case -2 0 eliminates any maximum size cutoff.
-3 filedescriptor-nr
Rewind the filedescriptor before invoking the (un)compression program if using the -Z option. This is useful when the -P and -Q options are used to replace the compression program gzip with some types of encryption programs in order to make or read an archive with encrypted files. The rewinding is needed to interface correctly with some encryption programs that read their key from an open filedescriptor. If the -P program name matches ’pgp’ or ’gpg’, then the -3 option must be used to avoid afio(1) reporting an error. Use the special case -3 0 to suppress the error message without rewinding any file descriptor. The -3 0 option may also be needed to successfully read back encrypted archives made with afio version 2.4.5 and older.
|
-4 |
(Deprecated, the intended effect of this option is now archived by default as long as the -5 option is not used. This option could still be useful for compatibility with machines running an older version of afio.) Write archive with the ’extended ASCII’ format headers which use 4-byte inode numbers. Archives using the extended ASCII format headers are not compatible with any other archiver. This option was useful for reliably creating and restoring sets of files with many internal hard links, for example a news spool. | ||
|
-5 |
Refuse to create an archive that is incompatible with cpio(1). If this option is used, afio will never write any ’large ASCII’ file headers that are incompatible with cpio(1), but fail with an error code instead. See the ARCHIVE PORTABILITY section above for more information on the use of ’large ASCII’ file headers. | ||
|
-6 filename |
While creating an archive with compressed files using the -Z option, disable (attempts at) compression for files that match particular shell patterns. This option can be used to speed up the creation of the archive, by making afio avoid trying to use gzip on files that contain compressed data already. Reads shell wildcard patterns from filename, treating each line in the file as a pattern. Files whose names match these patterns are not to be compressed when using the -Z option. Pattern matching is done in exactly the same way as described for the -y option. See also the -E option: the (default) settings of the -E option will further restrict compression attempts. The -E option controls compression attempts based on file extensions; the -6 option is mainly intended as a method for excluding all files in certain subdirectory trees from compression.. | ||
|
-7 |
Switch between shell wildcard pattern matching and exact name matching (without interpreting any wildcard characters) for the patterns supplied in the -y, -Y, -w, and -W options. If the -7 option is used in front of any option -y, -Y, -w, or -W, then the patterns supplied in these options are not intrerpreted as wildcard patterns, but as character strings that must match exactly to the file name, except possibly in leading slashes. This option can be useful for handling the exceptional cases where file names in the archive, or the names of files to be archived, contain wildcard characters themselves. For example, find /tmp -print0 | afio -ov -Y ’*.jpg’ -7 -Y ’/tmp/a[12]*4’ -0 archive can be used to archive files all files under /tmp, even files with a ’\n’ character in the name, except for .jpg files and the file with the exact name /tmp/a[12]*4. A second use of -7 toggles the matching for subsequently occurring -y, -Y, -w, and -W back to shell wildcard pattern matching. | ||
|
-8 directive |
Modify various behavior regarding symlinks. The directive nosymlinks applies to both archive creation and archive unpacking. During archive creation, it suppresses the inclusion of any symlink entry in the archive. In unpacking, it suppresses the unpacking of any symlink entry in the archive. This directive does not affect the interpretation of existing symlinks on the filesystem during the path resolution process where afio resolves the directory name components in front of the last / in a path name. The directive allowinsecurepaths applies to the security of archive unpacking. As of version 2.5.2, afio has protection mechanisms that apply to the unpacking of potentially untrusted archives. On unpacking, afio will by default (since version 2.5.2) inspect every pathname in the archive to detect the occurrence of a .. subpath in it. If one or more of these are present this is almost almost certainly due to the archive having been constructed by an attacker. The goal of the attack would be to have the afio unpacking operation over-write system or user files with new contents, via the use of using specially constructed path names like ../../../../../etc/password or ../../../../../home/a_user/.bashrc that resolve to the location of such configuration files. Therefore, if any .. subpaths are detected in a path name in an archive being unpacked, afio issues a warning, and then rewrites every ’..’ in the path name to ’XX’, and the archive entry is unpacked to the rewritten path name instead. The allowinsecurepaths directive disables the above rewriting of likely-insecure path names. Note that afio, while unpacking an archive, will also protect against that archive including potentially insecure path names that start with a leading /, by stripping off the leading / before using the path name is used, which has the effect of the archive entry relative to the current working directory. This stripping behavior can be disabled with the -A option. The directive allowinsecuresymlinks applies to a further the protection mechanism that applies to the unpacking of potentially untrusted archives. On unpacking, afio will by default (since version 2.5.2) inspect every symlink destination in the archive to detect the occurrence of a leading / or a .. subpath in it. If a leading / or .. subpaths are detected in the symlink destination, afio issues a warning, rewrites them to X or XX, and the result is used as the unpacked symlink destination instead. The allowinsecuresymlinks directive disables this protective rewriting behavior. Some further background: an attacking archive with an insecure symlink will typically include, as an entry after the insecure symlink, a file entry with a path that follows the insecure symlink leading to a location in the filesystem where a system or user configuration file can be overwritten. An archive with an insecure symlink may be created most easily an attacker who has the entire archive creation process under their control. However, in another case, the attacker is an untrusted end user on a multi-user system, where a trusted system administrator is creating a backup of a live file system containing directories under control of the untrusted end user. The untrusted end user can potentially exploit race conditions in the backup process, by creating temporary symlinks and files in their own home directory, resulting in in archive contents that would modify system configuration files when later unpacked if the protection mechanism were disabled using the allowinsecuresymlinks directive. The above described protection mechanisms are limited to symlinks. A untrusted archive attack that uses specially constructed hard link entries in the archive is theoretically possible with some archivers, but is not possible with afio, because of the special way that afio represents hard links in an archive. | ||
|
-9 |
Do not round down any -s volume sizes to the nearest -b block size. See the -s option. |
ARCHIVE PORTABILITY
afio archives are portable between different types of UNIX systems, as they contain only ASCII-formatted header information.
Except in special cases discussed below, afio will create archives with the same format as ASCII cpio(1) archives. Therefore cpio(1) can usually be used to restore an afio archive in the case that afio is not available on a system. (With most cpio versions, to unpack an ASCII format archive, use cpio -c, and for GNU cpio(1) use cpio -H odc.) When unpacking with cpio, any compressed files inside an afio -Z archive are not uncompressed by cpio, but will be created on the file system as compressed files with a .z extension.
Unfortunately, the ASCII cpio archive format cannot represent some files and file properties that can be present in a modern UNIX filesystem. If afio creates an archive with such things, then it uses an afio-specific ’large ASCII’ header for the files concerned. Archives with large ASCII headers cannot be unpacked completely by cpio or afio versions before 2.4.8.
When creating an archive, the ’large ASCII’ header is used by afio to cover the following situations:
|
o |
A file has a size larger than 2 GB | ||
|
o |
The archive contains more than 64K files which have hard links | ||
|
o |
A file, directory, or special file has a UID or GID value larger than 65535. |
The -5 option can be used to always preserve cpio compatibility, it will cause afio to fail rather than produce an incompatible archive in the cases above.
Archives made using the (deprecated) -4 option are also not compatible with cpio, but they are compatible with afio versions 2.4.4 and later.
ARCHIVE FILE FORMAT
An afio archive file has a simple format. The archive starts with a file header for the first file, followed by the contents of the first file (which will either be the exact contents byte-for-byte, or the exact contents in some compressed format). The data of the first file is immediately followed by the file header of the second file, and so on. At the end, there is a special ’end of archive’ header, usually followed by some padding bytes.
A multi-volume afio archive is simply a normal archive split up into multiple parts. There are no special volume-level data headers. This means that that volumes can be split and merged by external programs, as long as the data stays in the correct order. It also implies that the contents of a single file can cross volume boundaries. Selective restores of files at known volume locations can be done by feeding only the needed volumes to afio, provided that the -k option is used.
The contents of hard linked files are (unless the -l option is used) only stored once in the archive. The file headers for the second, third, and later occurrence of a hard linked file have no data after them. This makes selective restores of hard-liked files difficult: if later occurrences are to be restored correctly, the first occurrence always needs to be selected too.
NOTES
Special-case archive names:
|
o |
Specify - to read or write the standard input or output, respectively. This disables multi-volume archive handling. | ||
|
o |
Prefix a command string to be executed with an exclamation mark (!). The command is executed once for each archive volume, with its standard input or output piped to afio. It is expected to produce a zero exit code when all is well. | ||
|
o |
Use system:file to access an archive in file on system. This is really just a special case of pipelining. It requires a 4.2BSD-style remote shell (rsh(1C)) and a remote copy of afio. | ||
|
o |
A more elaborate case of the above is [user@]host[%rsh][=afio]:file where the optional user@ component specifies the user name on the remote host, the optional %rsh specifies the (local) name of the remote shell command to use, and the optional =afio specifies the name of the remote copy of the afio command. | ||
|
o |
Anything else specifies a local file or device. An output file will be created if it does not already exist. | ||
|
o |
When the -s option is used to invoke multi-volume archive processing, any %V in the file/device name or command string is subsisuted by the current volume number, and any %S by the current volume size. Use %% to produce a single % character. |
Recognizes obsolete binary cpio(1) archives (including those from machines with reversed byte order), but cannot write them.
Recovers from archive corruption by searching for a valid magic number. This is rather simplistic, but, much like a disassembler, almost always works.
CONTROL FILES
Afio archives can contain so-called control files. Unlike normal archive entries, a control file in not unpacked to the filesystem. A control file has a label and some data. When afio encounters a control file in the archive it is reading, it will feed the label and data to a so-called control script. The control script is supplied by the user. It can perform special actions based on the label and data it receives from afio.
Control file labels. The control file mechanism can be used for many things. Examples are putting archive descriptions at the beginning of the archive and embedding lists of files to move before unpacking the rest or the archive.
To distinguish between different uses, the label of a control file should indicate the program that made the control file and the purpose of the control file data. It should have the form
programname.kindofdata
where programname is the name of the backup program that generated the control file, and kindofdata is the meaning of the control file data. Some examples are
tbackup.movelist
tbackup.updatescript
blebberfiler.archivecontents
backup_script_of_Joe_User.archivedescription
The user-supplied control script should look at the label to decide what to do with the control data. This way, control files with unknown labels can be ignored, and afio archives maintain some degree of portability between different programs that restore or index them.
Control file labels that are intended to be portable between different backup programs could be defined in the future.
Making control files. When making an archive, afio reads a stream containing the names of the files (directories, ...) to put in the archive. This stream may also contain ’control file generators’, which are lines with the following format:
//--sourcename label
Here, the //-- sequence signals that a control file is to be made, sourcename is the path to a file containing the control file data, and label is the control file label. The sourcename must be a regular file or a symlink to a regular file.
A control file will show up as
//--CONTROL_FILE/label
in an archive listing, where label is the control file label.
Control scripts. A control script is supplied to afio with the
-D controlscript
command line option. The controlscript must be an executable program. The script is run whenever afio encounters a control file while doing a -i -t or -r operation. Afio will supply the control file label as an argument to the script. The script should read the control file data from its standard input. If the script exits with a non-zero exit status, afio will issue a warning message.
If a control file is encountered and no -D option is given, afio will issue a warning message. To suppress the warning message and ignore all control scripts, -D "" can be used.
An example of a control script is
#!/bin/sh
if [ $1 = "afio_example.headertext" ]; then
#the headertext control file is supposed to be packed as the
first
#entry of the archive
echo Archive header:
cat -
echo Unpack this archive? y/n
#stdout is still connected to the tty, read the reply from
stdout
read yn <&1
if [ "$yn" = n ]; then
#abort
kill $PPID
fi
else
echo Ignoring unknown control file.
cat - >/dev/null
fi
Afio never compresses the control file data when storing it in an archive, even when the -Z option is used. When a control file is encountered by cpio(1) or an afio with a version number below 2.4.1, the data will be unpacked to the filesystem, and named CONTROL_FILE/label where label is the control file label.
BUGS
There are too many options.
Restricts pathnames to 1023 characters, and 255 meaningful elements (where each element is a pathname component separated by a /).
Does not use the same default block size as tar(1). tar(1) uses 10 KB, afio uses 5 KB by default. Some tape drives only work with a 10 KB block size, in that case the afio option -b 10k is needed to make the tape work.
There is no sequence information within multi-volume archives. Input sequence errors generally masquerade as data corruption. A solution would probably be mutually exclusive with cpio(1) compatibility.
The afio code for handling floppies (-F and -f and -K options) has buggy error handling. afio does not allow one to retry a failed floppy write on a different floppy, and it cannot recover from a verify error. If the floppy handling code is used and write or verify errors do occur, it is best to restart afio completely. Making backups to floppies should really be done with a more specialised backup program that wraps afio.
The Linux floppy drivers below kernel version 1.1.54 do not allow afio to find out about floppy write errors while writing. If you are running a kernel below 1.1.54, afio will happily fail to write to (say) a write protected disk and not report anything wrong! The only way to find out about write errors in this case is by watching the kernel messages, or by switching on the verify (-K) option.
The remote archive facilites (host:/file archive names) have not been exhaustively tested. These facilities have seen a lot of real-life use though. However, there may be bugs in the code for error handling and error reporting with remote archives.
An archive created with a command like ’find /usr/src/linux -print | afio -o ...’ will not contain the ownership and permissions of the /usr and /usr/src directories. If these directories are missing when restoring the archive, afio will recreate them with some default ownership and permissions.
Afio can not restore time stamps on symlinks. Also, on operating systems without an lchown(2) system call, afio can not restore owner/group information on symlinks. (Linux has lchown since kernel version 2.1.86.)
Afio tries to restore modification time stamps of directories in the archive correctly. However, if it exits prematurely, then the modification times will not be restored correctly.
A restore using decompression will fail if the gzip binary used by afio is overwritten, by afio or by another program, during the restore. The restore will also fail if any shared libraries needed to start gzip are overwritten during the restore. afio should not normally be used to overwrite the system files on a running system. If it is used in this way, a flag like -Y /bin/gzip can often be added to prevent failure.
The -r option verifies the file contents of the files in the archive against the files on the filesystem, but does not cross-check details like permission bits on files, nor does it cross-check that archived directories or other non-file entities still exist on the filesystem.
There are several problems with archiving hard links. 1) Due to internal limitations, files with hard links cannot be stored in compressed form, unless the -l or -U options are used which force each hard linked file to be stored separately. 2) Archives which contain hard links and which were made with older (pre-2.4.8) versions of afio or with cpio can not always be correctly unpacked. This is really a problem in the archives and not in the current version of afio. The risk of incorrect unpacking will be greater if the number of files or hard links in the archives is larger. 3) In a selective restore, if the selection predicates do not select the first copy of a file with archive-internal hard links, then all subsequent copies, if selected, will not be correctly restored. 4) Unless the -4 option is used, the inode number fields in the archive headers for files with hard links of the archive will sometimes not contain the actual (least significant 16 bits of) the inode number of the original file.
Some Linux kernels no not allow one to create a hard link to a symbolic link. afio will try to re-create such hard links when unpacking an archive, but might fail due to kernel restrictions.
Due to internal limitations of afio, the use of the -U option forces the writing of file content with each hard linked file, rather than only once for every set of hard linked files.
When it is run without super-user privileges, afio is not able to unpack a file into a directory for which it has no write permissions, even if it just created that directory itself. This can be a problem when trying to restore directory structures created by some source code control tools like RCS.
When block or character device files are packed into an archive on one operating system (e.g. Linux) and unpacked on another operating system, which uses different sizes for the major and minor device number data types (e.g. Solaris), the major and minor numbers of the device files will not be restored correctly. This can be a problem if the operating systems share a cross-mounted filesystem. A workaround is to use tar(1) for the device files.
SECURITY CONSIDERATIONS
Security considerations arise when unpacking archives from untrusted sources. The recommended technique is to unpack such archives into a temporary, empty destination directory, unaccessible to other system users, while running afio as a normal user, so without superuser privileges. As of version 2.5.2, afio has security measures, enabled by default, to guard against a class of attacks where specially constructed path names and/or symlink destinations in an archive cause afio to to create or modify system or user files outside of the destination directory. See the -8 option for a more detailed description of these attacks and measures.
On UNIX
multi-user systems with untrusted users, there are several
known attacks where, unless the system administrator is very
careful, end users can exploit backup and restore activites
on the user filesystems to subvert data or operational
security. See e.g. the security section of the GNU
tar manual, at
http://www.gnu.org/software/tar/manual/html_node/Security.html
for a description of some issues and precautions.
An archive from an untrusted source could in theory contain mal-formatted data designed to implement a buffer overflow attack when afio reads the archive during a -t or -i operation. While the afio archive procesing code is fairly robust, and has passed some automated code checking tools, no formal review has been done to guarantee the absence of buffer overflow attack vulnerabilities. Running afio in a sandboxed virtual machine or from inside chroot(8) will improve the security of handling archives from untrusted sources, but the most secure option is to never touch such archives at all.
EXAMPLES
Create an
archive with compressed files:
find .... | afio -o -v -Z /dev/fd0H1440
Install
(unpack) an archive with compressed files:
afio -i -v -Z archive
Install
(unpack) an archive with compressed files, protecting newer
existing files:
afio -i -v -Z -n archive
Create an
archive with compressed files on floppy disks:
find .... | afio -o -v -s 1440k -F -Z /dev/fd0H1440
Create an
archive with all file contents encrypted by pgp:
export PGPPASSFD=3
find .... | afio -ovz -Z -U -P pgp -Q -fc -Q +verbose=0 -3 3
archive 3<passphrasefile
Create an
archive on recordable CDs using the cdrecord utility
to write each CD:
find .... | afio -o -b 2048 -s325000x -v ’!cdrecord
.... -’
Extract a
single named file from an archive on /dev/tape:
afio -i -v -Z -y /home/me/thedir/thefile /dev/tape
(If these do not exist yet, afio will also create the
enclosing directories home/me/myfiledir under current
working directory.)
Extract files
matching a pattern from an archive on /dev/tape:
afio -i -v -Z -y ’/home/me/*’ /dev/tape
(If these do not exist yet, afio will also create the
enclosing directories home/me under current working
directory.)
If your
filesystem cannot handle files larger than 2GB, but you want
to make an archive on that filesystem that is larger than
2GB, you use the following trick to split the archive into
multiple files of each 1 GB:
find /home | afio -o ... - | split -b1024m - archive.
the files will be called archive.aa, archive.ab, etc. You
can restore the whole archive using:
cat archive.* | afio -i ... -
The wildcard expansion by the shell will ensure that
cat will read the parts in the right (alphabetic)
order.
SEE ALSO
cpio(1), find(1), tar(1), compress(1), gzip(1).
WEB SITE AND INTERNET RESOURCES
The afio home
page is at http://members.chello.nl/~k.holtman/afio.html
See the home page for information on submitting questions,
bug reports, patches, etc.
AUTHORS
Mark Brukhartz
Jeff Buhrt
Dave Gymer
Andrew Stevens
Koen Holtman (current maintainer)
koen.holtman [AT] ieee.org
Anders Baekgaard
Too many other people to list here have contributed code,
patches, ideas, and bug reports. Many of these are mentioned
in the HISTORY file that is included with the sources.