apt - What happens to dependent Debian packages when you upgrade a Debian package? - Ask Ubuntu

let's have debian package a-1.0.0.deb (which contains library), , package b-1.0.0.deb (which contains service) depends on a library. let's want upgrade a-1.0.1.deb.

according this document, dpkg goes through pretty involved algorithm figure package maintainer scripts called each package part of upgrade process. if of these steps fail, a can left in sort of limbo state (for example, "half-installed").

however, when break a, b broken since depends on a. question dpkg have built-in way deal situation? b's install status change depending on a's status? ideally dpkg have built-in functionality move b installed state state (so b service can stopped & restarted when a healthy), can't find in dpkg documentation suggests done.

if dpkg doesn't handle situation intelligently, apt?

from have experienced not have read.

• however, when break a, b broken since depends on it. question dpkg have built-in way deal situation?

  yes, try reinstall or reconfigure on next run.

  1. if interrupted, fix , continue working normal.

  2. but it's problem control scripts, fail again , again , stay in loop. it's bug , report filled against package , manual fix required.

• does b's install status change depending on a's status?

  no, status stay installed no change, keep track of broken dependency too, @ least not in same file /var/lib/dpkg/status.

• if dpkg doesn't handle situation intelligently, apt?

  no, apt not interfere in case. apt uses dpkg, dpkg lower level tool , tool install, build, remove debian packages.

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let's try it, better done in virtualbox.

1. prepare dummy packages

   ~$ sudo apt install equivs ~$ mkdir deleteme ~$ cd deleteme 

   b 1.0.0 depends on a

   ~/deleteme$ equivs-control b0 ~/deleteme$ nano b0 ... package: b version: 1.0.0 ... depends: ... ~/deleteme$ equivs-build b0 

   a 1.0.0 clean install & remove

   ~/deleteme$ equivs-control a0 ~/deleteme$ nano a0 ... package: version: 1.0.0 ... ~/deleteme$ equivs-build a0 

   a 1.0.1 dirty install, clean remove

   ~/deleteme$ cp a0 a1 ~/deleteme$ nano a1 ... package: version: 1.0.1 ... postinst: a1.postinst ...  ~/deleteme$ nano a1.postinst  #!/bin/sh     exit 1  ~/deleteme$ equivs-build a1 

   now, should have:

   ~/deleteme$ ls -1 a0 a1 a_1.0.0_all.deb a_1.0.1_all.deb a1.postinst b0 b_1.0.0_all.deb 

2. try scenario

   sudo su  dpkg -i b_1.0.0_all.deb dpkg --audit dpkg -i a_1.0.0_all.deb dpkg --audit dpkg --configure -a dpkg --audit dpkg --remove dpkg --remove b dpkg --remove  dpkg -i a_1.0.0_all.deb dpkg -i b_1.0.0_all.deb dpkg --audit dpkg -i a_1.0.1_all.deb dpkg --audit dpkg --remove apt purge 

3. to in loop can't complete installation neither remove it.

   create clean 1.0.1, b 1.0.0 1.0.0 prerm: script contains exit 1. when try install 1.0.1, dpkg fail remove 1.0.0 .