[SOLVED] tar making a fuss

phalange · 05-20-2020, 11:32 AM

So I've been playing with a lot of RPI images lately and some come compressed as *xz and *bz2 files.

tar -xf has been more often than not kicking up this error:

Code:

tar: This does not look like a tar archive
tar: Skipping to next header
tar: Exiting with failure status due to previous errors

Using Ark 2.19 that comes with Slackware gives no trouble. I just extract the img file as expected.

On -Current with tar 1.32

karlmag · 05-20-2020, 11:59 AM

Quote:

Originally Posted by phalange

So I've been playing with a lot of RPI images lately and some come compressed as *xz and *bz2 files.

tar -xf has been more often than not kicking up this error:

Code:

tar: This does not look like a tar archive
tar: Skipping to next header
tar: Exiting with failure status due to previous errors

Using Ark 2.19 that comes with Slackware gives no trouble. I just extract the img file as expected.

On -Current with tar 1.32

From tars manpage;

Code:

       -j, --bzip2
              Filter the archive through bzip2(1).

       -J, --xz
              Filter the archive through xz(1).

Also; what does the 'file' command say about the files?

--
KarlMag

phalange · 05-20-2020, 12:19 PM

Quote:

Originally Posted by karlmag

From tars manpage;

Code:

-j, -J

same result

Quote:

Originally Posted by karlmag

Also; what does the 'file' command say about the files?

*.img.bz2: bzip2 compressed data, block size = 900k

shruggy · 05-20-2020, 12:24 PM

Quote:

Originally Posted by phalange

*.img.bz2: bzip2 compressed data, block size = 900k

This ^.

Quote:

Ark manages various archive formats, including tar, gzip, bzip2, rar and zip,
as well as CD-ROM images.

phalange · 05-20-2020, 12:30 PM

Quote:

Originally Posted by shruggy

This ^.

So is the issue that I've been looking at tar.bz2 files for so many years that I mistakenly assumed these are tar archives when they are not, and thus fall outside the functionality of the tar program? Seems like this may be the case.

shruggy · 05-20-2020, 12:31 PM

I believe those images were created with dd. They a just byte-for-byte copies of SD card contents. Ark uses libarchive internally, and libarchive can handle "raw" archive format whatever that means. Edit. Raw just means compressed data without any archive structure.

This also means that bsdtar, which also uses libarchive, may be able to handle those archives as well.

phalange · 05-20-2020, 12:40 PM

Quote:

Originally Posted by shruggy

I believe the images are just created with dd.

Ok cool. I just tried bunzip2 *.bz2 and it did the trick. I've not used bunzip2 maybe ever.

pan64 · 05-20-2020, 12:58 PM

In general tar should automatically detect bzip2 format and also you can use -j to [un]compress.
So it was not the usual case.
Anyway, if your problem solved please mark the thread solved.

phalange · 05-20-2020, 01:01 PM

Thanks folks, looks like I asked tar to do something it's not meant to do. bunzip2 program solved the problem.

average_user · 05-20-2020, 01:35 PM

Quote:

Originally Posted by karlmag

From tars manpage;

Code:

       -j, --bzip2
              Filter the archive through bzip2(1).

       -J, --xz
              Filter the archive through xz(1).

GNU tar recognizes archive types automatically since 2004 https://www.gnu.org/software/tar/:

Quote:

Compressed archives are recognised automatically, it is no longer necessary to specify -Z, -z, or -j options to read them. Thus, you can now run tar tf archive.tar.gz and expect it to work!

bassmadrigal · 05-20-2020, 02:40 PM

Quote:

Originally Posted by average_user

GNU tar recognizes archive types automatically since 2004 https://www.gnu.org/software/tar/:

This doesn't always work, but usually does. If you are piping into tar, you need to manually specify the archive type and it seems that OP found another exception to the rule.

average_user · 05-20-2020, 03:04 PM

You don't pass a file name when you read contents of an archive from standard input so it obviously doesn't work.

And OP has not found "exception to the rule" but uses tar on non-tar files so in other words they don't know what they're doing.

Anyway, there is no need to remember what programs you should use to extract a given archive file and with what parameters, just create `ext' function that looks like that:

Code:

$ type ext
ext is a function
ext ()
{
    if [ -f "$1" ]; then
        case "$1" in
            *.tar.bz2)
                tar xvjf "$1"
            ;;
            *.tar.gz)
                tar xvzf "$1"
            ;;
            *.tar.xz)
                tar Jxvf $1
            ;;
            *.bz2)
                bunzip2 "$1"
            ;;
            *.rar)
                unrar x "$1"
            ;;
            *.gz)
                gunzip "$1"
            ;;
            *.tar)
                tar xvf "$1"
            ;;
            *.tbz2)
                tar xvjf "$1"
            ;;
            *.tgz)
                tar xvzf "$1"
            ;;
            *.zip)
                unzip "$1"
            ;;
            *.Z)
                uncompress "$1"
            ;;
            *.7z)
                7z x "$1"
            ;;
            *.txz)
                tar Jxvf "$1"
            ;;
            *)
                echo "'$1' cannot be extracted";
                return 1
            ;;
        esac;
    else
        echo "'$1' is not a valid file";
        return 1;
    fi;
    return 0
}

phalange · 05-20-2020, 03:27 PM

Quote:

Originally Posted by average_user

And OP has not found "exception to the rule" but uses tar on non-tar files so in other words they don't know what they're doing.

Thanks for the suggestion. This thread in not an invitation for a personal attack.

average_user · 05-20-2020, 03:44 PM

Stating facts is hardly a personal attack, you cannot be so fragile. You use the wrong tool for the job.

bassmadrigal · 05-20-2020, 04:16 PM

Quote:

Originally Posted by average_user

Stating facts is hardly a personal attack, you cannot be so fragile. You use the wrong tool for the job.

And that sure is a nice way of letting OP know that "I'm better than you and you should know it".

You could've simply stated that the files were not created by tar and so tar doesn't know what to do unless you specify it, but instead you have to be a jerk about it and slam OP instead of using it as a simple teaching moment.

There once was a time when you didn't know what you were doing with tar, other aspects of computers, or life in general. You have to start somewhere. Even if someone has a ton of experience, sometimes brainfarts happen or it's just something they haven't run into. That's no reason to be rude.

I'm not saying this as someone who was offended or speculating whether or not OP was offended, but in a forum where we like to spread knowledge about Slackware and Linux, you can use some tact when presenting information that is contrary to what they originally thought.