The man page for tar uses the word "dump" and its forms several times. What does it mean? For example (manual page for tar 1.26):
"-h, --dereferencefollow symlinks; archive and dump the files they point to"
Many popular systems have a "trash can" or "recycle bin." I don't want the files dumped there, but it kind of sounds that way.
At present, I don't want tar to write or delete any file, except that I want tar to create or update a single tarball.
FYI, the man page for the tar installed on the system I am using at the moment is a lot shorter than what appears to be the current version. And the description of -h, --dereference there seems very different to me:
"When reading or writing a file to be archived, tar accesses the file that a symbolic link points to, rather than the symlink itself. See section Symbolic Links."
P.S. I could not get "block quote" to work properly in this post.
File system backups are also called dumps.
—#raymond-chen, quoting GNU tar manual
Related
I have a container that I want to export as a .tar file. I have used a podman run with a tar --exclude=/dir1 --exclude=/dir2 … that outputs to a file located on a bind-mounted host dir. But recently this has been giving me some tar: .: file changed as we read it errors, which podman/docker export would avoid. Besides the export I suppose is more efficient. So I'm trying to migrate to using the export, but the major obstacle is I can't seem to find a way to exclude paths from the tar stream.
If possible, I'd like to avoid modifying a tar archive already saved on disk, and instead modify the stream before it gets saved to a file.
I've been banging my head for multiple hours, trying useless advices from ChatGPT, looking at cpio, and attempting to pipe the podman export to tar --exclude … command. With the last I did have small success at some point, but couldn't make tar save the result to a particularly named file.
Any suggestions?
(note: I do not make distinction between docker and podman here as their export command is completely the same, and it's useful for searchability)
Problem outline
I'm trying to get all the files from an URL: https://archive-gw-1.kat.ac.za/public/repository/10.48479/7epd-w356/data/basic_products/bucket_contents.html
which appears to be a list of contents of an S3 bucket with associated download links.
When I attempt to download all the files with the extension *.jpeg, I'm simply returned the directory structure leading up to an subdirectory with no downloaded files.
Things I've tried
To do this I've tried all the variations of leading parameters for:
$ wget -r -np -A '*.jpeg' https://archive-gw-1.kat.ac.za/public/repository/10.48479/7epd-w356/data/basic_products/
...that I can think of, but none have actually downloaded the jpeg files.
If you provide the path to a specific file e.g.
$ wget https://archive-gw-1.kat.ac.za/public/repository/10.48479/7epd-w356/data/basic_products/Abell_133_hi.jpeg
...the files can be downloaded, which would suggest that I must be mishandling the wildcard aspect of the download surely?
Thoughts which could be wrong owing to limited knowledge of wget and website protocols
Unless the fact that the contents are held in a bucket_contents.html rather than an index.html is causing problems?
I'm making a tarball of a directory with tar -C "$DIR" -chf "$TARBALL" and a few files keep giving me the warning, "File removed before we read it". The files are there, and I'm not running any other processes at the same time that could be writing over the files.
What does this error mean?
Because of the -h flag, tar needs to follow any symbolic links it finds. Any broken symbolic link will give the error "File removed before we read it" e.g. symbolic links that no longer lead to valid files.
Either:
make sure all the links point to valid files
remove all the invalid links
remove the -h flag, to shallow copy the links (rather than the files they point to)
we run an rsync on a large folder. This has close to a million files inside it including html, jsp, gif/jpg, etc. We only need to of course incrementally update files. Just a few JSP and HTML files are updated in this folder, and we need this server to rsync to a different server, same folder.
Sometimes rsync is running quite slow these days, so one of our IT team members created this command:
find /usr/home/foldername \
-type f -name *.jsp -exec \
grep -l <ssi:include src=[^$]*${ {} ;`
This looks for only specific files which have JSP extension and which contain certain kinds of text, because these are the files which we need to rsync. But this command is consuming a lot of memory. I think it's a stupid way to rsync, but I'm being told this is how things will work.
Some googling suggests that this should work on this folder too:
rsync -a --update --progress --rsh --partial /usr/home/foldername /destination/server
I'm worried that this will be too slow on a daily basis, but I can't imagine why this will be slower than that silly find option that our IT folks are recommending. Any ideas about large directory rsyncs in the real world?
A find command will not be faster than the rsync scan, and the grep command must be slower than rsync because it requires reading all the text from all the .jsp files.
The only way a find-and-grep could be faster is if
The timestamps on your files do not match, so rsync has to checksum the contents (on both sides!)
This seems unlikely, since you're using -a that will sync the timestamps properly (because -a implies -t). However, it can happen if the file-systems on the different machines allow different timestamp precision (e.g. Linux vs. Windows), in which case the --modify-window option is what you need.
There are many more files changed than the ones you care about, and rsync is transferring those also.
If this is the case then you can limit the transfer to .jsp files like this:
--include '*.jsp' --include '*/' --exclude '*'
(Include all .jsp files and all directories, but exclude everything else.)
rsync does the scan up front, then does the compare (possibly using lots of RAM), then does the transfer, where as find/grep/copy does it now.
This used to be a problem, but rsync ought to do an incremental recursive scan as long as both local and remote versions are 3.0.0 or greater, and you don't use any of the fancy delete or delay options that force an up-front scan (see --recursive in the documentation).
AIX6.1, I use java to execute a tar command to extract a tar package. one stange thing I met is that some files with long name in thi tar package failed to be extracted to where they should be. but occurs at current working folder. and the file owner of these files are not correct too.
I googled and found that there many post for use GUN tar instead to avoid long file name issue. but I am sure this is not the same issue as I met.
is there anyone know why this happen? any tips are appreciate much. thanks.
The man pages are pretty instructive on this topic. Probably your tar file is not strictly POSIX compatible. On AIX:
The prefix buffer can be a maximum of 155 bytes and the name buffer can
hold a maximum of 100 bytes. If the path name cannot be split into
these two parts by a slash, it cannot be archived.
The Linux man page for GNU tar says it can handle a variety of tar file format variants. One of these is the 'ustar' POSIX standard, which appears to be the one handled by AIX tar. There is a separate gnu format, which is the default for GNU tar.
I'd suspect you're opening a GNU tar archive with a tar tool which only understands the POSIX standard, and it can't quite cope.