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Accepted
Manuel Jordan
Asked: 2022-11-18 19:08:47 +0800 CST

Where is the unpacked content of a .deb file when using the "--unpack" option of dpkg?

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About the dpkg command, a few tutorials do mention of the --unpack option. According with jammy (1) dpkg.1 it indicates

--unpack package-file...
   Unpack the package, but don't configure it. If --recursive or -R option is specified,
   package-file must refer to a directory instead.

Well just how testing, from the MySQL APT Repository page it is possible to get the mysql-apt-config_0.8.24-1_all.deb file. So in the Downloads directory I executed the command:

sudo dpkg --unpack mysql-apt-config_0.8.24-1_all.deb

It works with the following message

(Reading database ... 238377 files and directories currently installed.)
Preparing to unpack mysql-apt-config_0.8.24-1_all.deb ...
Unpacking mysql-apt-config (0.8.24-1) over (0.8.24-1) ...

Even when MySQL is installed.

Question

  • Where is the unpacked the content of a .deb file?

A simple execution of the ls command only shows the current .deb file. I expected a kind of extraction. I am assuming a kind of default directory or other something else was used.

If with the -c option, it is possible to see the directories of the .deb file I am assuming that the --unpack option unpacks the .deb file - if my assumption is incorrect about the latter, please correct me.

package-management

1 Answers

  1. Best Answer

    If you look at the part immediately about --unpack in the manpage (for --install):

    Installation consists of the following steps:

    1. Extract the control files of the new package.

    2. If another version of the same package was installed before the new installation, execute prerm script of the old package.

    3. Run preinst script, if provided by the package.

    4. Unpack the new files, and at the same time back up the old files, so that if something goes wrong, they can be restored.

    5. If another version of the same package was installed before the new installation, execute the postrm script of the old package. Note that this script is executed after the preinst script of the new package, because new files are written at the same time old files are removed.

    6. Configure the package. See --configure for detailed information about how this is done.

    Step 4 would seem to indicate that to unpack means to put the files in the package wherever they are supposed to be in the final state of the system. So if the package was supposed to install a /usr/bin/foo or an /etc/bar/baz file, then unpacking will put the corresponding files at those locations.

    If you wanted to extract the files to the current directory or something like that instead of extracting them to the final installation targets, then the option is -x or --extract:

    -x, --extract archive directory
   Extract the files contained by package.

-X, --vextract archive directory
   Extract and display the filenames contained by a package.
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