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user1424739
Asked: 2021-02-07 09:03:41 +0800 CST

Where are the database files queried by dpkg-query?

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I don't see where are the database files checked by dpkg-query -S in its manpage. Could anybody let me know where it is? Thanks.

dpkg

1 Answers

  1. It depends upon exactly what kind of query you do, but all of dpkg's database files are under /var/lib/dpkg. They are often plain text files.

    For example, a simple dpkg-query -l will find what it needs in /var/lib/dpkg/status:

    $ strace -e trace=open,openat dpkg-query -l base-files
openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
openat(AT_FDCWD, "/usr/lib/locale/locale-archive", O_RDONLY|O_CLOEXEC) = 3
openat(AT_FDCWD, "/var/lib/dpkg/arch", O_RDONLY) = 3
openat(AT_FDCWD, "/var/lib/dpkg/status", O_RDONLY) = 3
openat(AT_FDCWD, "/usr/share/locale/locale.alias", O_RDONLY|O_CLOEXEC) = 4
openat(AT_FDCWD, "/usr/share/locale/en_GB/LC_MESSAGES/dpkg.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/share/locale/en/LC_MESSAGES/dpkg.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/share/locale-langpack/en_GB/LC_MESSAGES/dpkg.mo", O_RDONLY) = 4
openat(AT_FDCWD, "/usr/share/locale-langpack/en/LC_MESSAGES/dpkg.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/var/lib/dpkg/updates/", O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_DIRECTORY) = 3
openat(AT_FDCWD, "/var/lib/dpkg/triggers/File", O_RDONLY) = 3
openat(AT_FDCWD, "/var/lib/dpkg/triggers/Unincorp", O_RDONLY) = 3
openat(AT_FDCWD, "/dev/tty", O_RDONLY)  = 4
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
openat(AT_FDCWD, "/usr/lib/x86_64-linux-gnu/gconv/gconv-modules.cache", O_RDONLY) = 4
||/ Name              Version       Architecture  Description
+++-=================-=============-=============-=======================================
ii  base-files        10.1ubuntu2.1 amd64         Debian base system miscellaneous files
+++ exited with 0 +++

    Update: Question has been changed from simple dpkg-query to specify dpkg-query -S. So to answer that:

    As mentioned, exactly where dpkg-query looks depends upon what type of query you do, but all of its information exists below /var/lib/dpkg/. For dpkg-query -S queries for example, it examines every *.list file in /var/lib/dpkg/info/:

    $ strace -e trace=open,openat dpkg-query -S /bin/ls 
[…]
openat(AT_FDCWD, "/var/lib/dpkg/info/fonts-sil-abyssinica.list", O_RDONLY) = 4
openat(AT_FDCWD, "/var/lib/dpkg/info/libatk-adaptor:amd64.list", O_RDONLY) = 4
openat(AT_FDCWD, "/var/lib/dpkg/info/libvorbisfile3:amd64.list", O_RDONLY) = 4
openat(AT_FDCWD, "/var/lib/dpkg/info/libquadmath0:amd64.list", O_RDONLY) = 4
[…]
openat(AT_FDCWD, "/var/lib/dpkg/info/tzdata.list", O_RDONLY) = 4                             
openat(AT_FDCWD, "/var/lib/dpkg/diversions", O_RDONLY) = 4                                   
coreutils: /bin/ls                                                                           
+++ exited with 0 +++
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