Thread: Database backup
Hello everybody! I use postgresql for long time now, all through libpq (wich I think is the most exciting interface) and everything is fine. When I wanted to backup the base, I was using: "pg_dump mybase > mybase.pgd"and "cat mybase.pgd|psql mybase" (don't careabout OIDs) I faced some small problems to finalise the conversion settings between different versions, but at the end everything was fine. Question: Am I too stupid to use tar? Some time I had no space on the filesystem to copy all the data in command mode (pg_dump) so I thought to pipe pg_dump to tar using a scsi tape archiver as output (/dev/rmt0). Why doesn't work? Using just pg_dump we have the output to stdout. I thought that I missender a parameter or something. If this is the case, sorry everybody for bothering - I'm just too stupid to use the pipe to tar. In this case, PLEASE someone drop a line correcting the syndax for me. If is not, then we have to thing about piping pg_dump to tape archive. //a command line view: # pg_dump mybase|tar cvf /dev/rmt0 - // (and some other versions) tar: -: Cannot stat: No such file or directory tar: Error exit delayed from previous errors # tar xvf /dev/rmt0|psql mybase EOF // (!!!) # after the "EOF" message from psql the database is, of cource, empty. ***************** thanks, Alexandros
Redirecting to help list as it seems more appropriate.
On Saturday 18 January 2003 09:17, Alexandros Perdikomatis wrote:
> Question: Am I too stupid to use tar?
I'm sure not but you may misunderstand what tar does. Tar is for storing a
collection of files into an archive. It expects to find the list of files on
the command line in one form or another. If you don't write to a file first
then all you have is a stream of data, not a file.
> Some time I had no space on the filesystem to copy all the data in command
> mode (pg_dump) so I thought to pipe pg_dump to tar using a scsi tape
> archiver as output (/dev/rmt0).
> Why doesn't work?
What exactly was the problem? You may just have a device selection issue.
What system is this on?
--
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Στις Κυρ 19 Ιαν 2003 04:59, ο/η D'Arcy J.M. Cain έγραψε: > Redirecting to help list as it seems more appropriate. > > On Saturday 18 January 2003 09:17, Alexandros Perdikomatis wrote: > > Question: Am I too stupid to use tar? > > I'm sure not but you may misunderstand what tar does. Tar is for storing a > collection of files into an archive. It expects to find the list of files > on the command line in one form or another. If you don't write to a file > first then all you have is a stream of data, not a file. > > > Some time I had no space on the filesystem to copy all the data in > > command mode (pg_dump) so I thought to pipe pg_dump to tar using a scsi > > tape archiver as output (/dev/rmt0). > > Why doesn't work? > > What exactly was the problem? You may just have a device selection issue. > What system is this on? Thanks for the reply. I think I understand what you mean, I just thought that instead of a file input, we could have a pipe input. It runs on a SuSE linux 6.4 (you may ask why this old version, I updated what was necesary, I like it becouse I have full greek support) and the archiver is an old conner DDS-2 scsi tape streamer which is known on the operating system as /dev/st0 by the kernel whith a symbolic link to /dev/rmt0. When I pg_dump on a file, of cource there's no problem. I restore also correctly. But I would like to pipe this procces. For example: if we type the command: # tar cvf /dev/rmt0 * we're going to have all the files in the tree below to the tape. How can I pipe the output of the pg_dump to it? Thank you one more time for your reply, I just feel that it must be a way with it. I face no problems in my C programs using postgresql, (I like it so much) so I also feel that this problem sould not be in this mailing list becouse maybe is a system-side question. If this is the case, sorry everybody. (one question: where (which mailing list, book or something) is going to help me installing postgresql to an IBM AiX 4.3 system (RS6000 architecture)? (please) thanks again. Alexandros
On Sun, 19 Jan 2003, Alexandros Perdikomatis wrote: > Óôéò Êõñ 19 Éáí 2003 04:59, ï/ç D'Arcy J.M. Cain Ýãñáøå: > > Redirecting to help list as it seems more appropriate. > > > > On Saturday 18 January 2003 09:17, Alexandros Perdikomatis wrote: > > > Question: Am I too stupid to use tar? > > > > I'm sure not but you may misunderstand what tar does. Tar is for storing a > > collection of files into an archive. It expects to find the list of files > > on the command line in one form or another. If you don't write to a file > > first then all you have is a stream of data, not a file. > > > > > Some time I had no space on the filesystem to copy all the data in > > > command mode (pg_dump) so I thought to pipe pg_dump to tar using a scsi > > > tape archiver as output (/dev/rmt0). > > > Why doesn't work? > > > > What exactly was the problem? You may just have a device selection issue. > > What system is this on? > > Thanks for the reply. > I think I understand what you mean, I just thought that instead of a file > input, we could have a pipe input. > It runs on a SuSE linux 6.4 (you may ask why this old version, I updated what > was necesary, I like it becouse I have full greek support) and the archiver > is an old conner DDS-2 scsi tape streamer which is known on the operating > system as /dev/st0 by the kernel whith a symbolic link to /dev/rmt0. > When I pg_dump on a file, of cource there's no problem. I restore also > correctly. > But I would like to pipe this procces. For example: if we type the command: > # tar cvf /dev/rmt0 * > we're going to have all the files in the tree below to the tape. > How can I pipe the output of the pg_dump to it? Well, you could do: pg_dump ... > /dev/rmt0 or if you want to set block size: pg_dump ... | dd of=/dev/rmt0 obs=1k Basically, you're trying to make it too complicated, tar will archive one file but would you really use something like: tar -cf archived-file.tar unarchived-file unless the unarchived-file name was generated automatically and it just so happened that only one file existed at that time? If you really do want something tar try cpio instead. -- Nigel J. Andrews
Στις Κυρ 19 Ιαν 2003 20:23, ο/η Nigel J. Andrews έγραψε: > On Sun, 19 Jan 2003, Alexandros Perdikomatis wrote: > > Óôéò Êõñ 19 Éáí 2003 04:59, ï/ç D'Arcy J.M. Cain Ýãñáøå: > > > Redirecting to help list as it seems more appropriate. > > > > > > On Saturday 18 January 2003 09:17, Alexandros Perdikomatis wrote: > > > > Question: Am I too stupid to use tar? > > > > > > I'm sure not but you may misunderstand what tar does. Tar is for > > > storing a collection of files into an archive. It expects to find the > > > list of files on the command line in one form or another. If you don't > > > write to a file first then all you have is a stream of data, not a > > > file. > > > > > > > Some time I had no space on the filesystem to copy all the data in > > > > command mode (pg_dump) so I thought to pipe pg_dump to tar using a > > > > scsi tape archiver as output (/dev/rmt0). > > > > Why doesn't work? > > > > > > What exactly was the problem? You may just have a device selection > > > issue. What system is this on? > > > > Thanks for the reply. > > I think I understand what you mean, I just thought that instead of a file > > input, we could have a pipe input. > > It runs on a SuSE linux 6.4 (you may ask why this old version, I updated > > what was necesary, I like it becouse I have full greek support) and the > > archiver is an old conner DDS-2 scsi tape streamer which is known on the > > operating system as /dev/st0 by the kernel whith a symbolic link to > > /dev/rmt0. When I pg_dump on a file, of cource there's no problem. I > > restore also correctly. > > But I would like to pipe this procces. For example: if we type the > > command: # tar cvf /dev/rmt0 * > > we're going to have all the files in the tree below to the tape. > > How can I pipe the output of the pg_dump to it? > > Well, you could do: > > pg_dump ... > /dev/rmt0 > > or if you want to set block size: > > pg_dump ... | dd of=/dev/rmt0 obs=1k > > Basically, you're trying to make it too complicated, tar will archive one > file but would you really use something like: > > tar -cf archived-file.tar unarchived-file > > unless the unarchived-file name was generated automatically and it just so > happened that only one file existed at that time? > > If you really do want something tar try cpio instead. Thanks for the information, I should think about piping to dd... thanks again. The idea of cpio looks more interesting becouse we could have a multivolume archive I suppose. one more time thanks, Alexandros