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Operating Systems Solaris UNIX : how can I recover a corrupt tar file from a tape? Post 302965073 by hicksd8 on Saturday 23rd of January 2016 08:57:07 AM
Old 01-23-2016
Lots of questions to ask about this.

Do you know for certain that it's a tar tape and not cpio or some other proprietary format?

Sometimes tape formats have a header so use a no rewind 'nr' device to prevent rewinding, stopping the tape where it is, and then try again.

Do you know the blocking factor the tape was written in?
If you're trying to read it raw with dd, trying appending each of bs=512, bs=1024, bs=2048 and bs=4096 to the dd command. Perhaps tar was configured to write a different block factor to what dd is defaulted.

DAT's always know internally (without reference to the O/S) if they are reading junk. The DAT mechanism writes enough checksums (created by the drive) to know when the integrity of the data is compromised.

---------- Post updated at 01:57 PM ---------- Previous update was at 11:57 AM ----------

Other thoughts are:-

also try bs=10240 in case it's written with the commonly used block size of 10k

Was the tape written by this DAT drive? Tape transports can go out of alignment (the posts that guide the tape) so you may well find that if you put the tape into the drive that wrote it, it will read with no problem.
 

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SMBTAR(1)							   User Commands							 SMBTAR(1)

NAME
smbtar - shell script for backing up SMB/CIFS shares directly to UNIX tape drives SYNOPSIS
smbtar [-r] [-i] [-a] [-v] {-s server} [-p password] [-x services] [-X] [-N filename] [-b blocksize] [-d directory] [-l loglevel] [-u user] [-t tape] {filenames} DESCRIPTION
This tool is part of the samba(7) suite. smbtar is a very small shell script on top of smbclient(1) which dumps SMB shares directly to tape. OPTIONS
-s server The SMB/CIFS server that the share resides upon. -x service The share name on the server to connect to. The default is "backup". -X Exclude mode. Exclude filenames... from tar create or restore. -d directory Change to initial directory before restoring / backing up files. -v Verbose mode. -p password The password to use to access a share. Default: none -u user The user id to connect as. Default: UNIX login name. -a Reset DOS archive bit mode to indicate file has been archived. -t tape Tape device. May be regular file or tape device. Default: $TAPE environmental variable; if not set, a file called tar.out . -b blocksize Blocking factor. Defaults to 20. See tar(1) for a fuller explanation. -N filename Backup only files newer than filename. Could be used (for example) on a log file to implement incremental backups. -i Incremental mode; tar files are only backed up if they have the archive bit set. The archive bit is reset after each file is read. -r Restore. Files are restored to the share from the tar file. -l log level Log (debug) level. Corresponds to the -d flag of smbclient(1). ENVIRONMENT VARIABLES
The $TAPE variable specifies the default tape device to write to. May be overridden with the -t option. BUGS
The smbtar script has different options from ordinary tar and from smbclient's tar command. CAVEATS
Sites that are more careful about security may not like the way the script handles PC passwords. Backup and restore work on entire shares; should work on file lists. smbtar works best with GNU tar and may not work well with other versions. DIAGNOSTICS
See the DIAGNOSTICS section for the smbclient(1) command. VERSION
This man page is correct for version 3 of the Samba suite. SEE ALSO
smbd(8), smbclient(1), smb.conf(5). AUTHOR
The original Samba software and related utilities were created by Andrew Tridgell. Samba is now developed by the Samba Team as an Open Source project similar to the way the Linux kernel is developed. Ricky Poulten wrote the tar extension and this man page. The smbtar script was heavily rewritten and improved by Martin Kraemer. Many thanks to everyone who suggested extensions, improvements, bug fixes, etc. The man page sources were converted to YODL format (another excellent piece of Open Source software, available at ftp://ftp.icce.rug.nl/pub/unix/) and updated for the Samba 2.0 release by Jeremy Allison. The conversion to DocBook for Samba 2.2 was done by Gerald Carter. The conversion to DocBook XML 4.2 for Samba 3.0 was done by Alexander Bokovoy. Samba 3.5 06/18/2010 SMBTAR(1)
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