Debian Sid: downgrading a single package to a "previous version"

Question

I am happily running a state-of-art Debian Sid workstation.

Unfortunately I incurred in an "upstream regression" (network-manager-vpnc broke 1.2.7 -> 1.2.8)

I thus need to "downgrade" to a previous revision.

I am aware I should be able to do it with something like:

sudo apt install network-manager-vpnc=1.2.7

but that doesn't seem to work for Sid as I get:

sudo apt policy network-manager-vpnc
network-manager-vpnc:
  Installed: 1.2.8-3
  Candidate: 1.2.8-3
  Version table:
 *** 1.2.8-3 500
        500 http://deb.debian.org/debian sid/main amd64 Packages
        100 /var/lib/dpkg/status

which means only a single version is available and thus the error is unsurprising:

sudo apt install network-manager-vpnc=1.2.7
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Package network-manager-vpnc is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Version '1.2.7' for 'network-manager-vpnc' was not found

What can I do?

Update: as @Stephen-Kitt correctly states "previous version" (1.2.7) was never uploaded to Debian archives so "solution" was to downgrade to 1.2.6-3.

Procedure to get to a working system (for me) was:

mcon@cinderella:/tmp/t$ wget http://ftp.it.debian.org/debian/pool/main/n/network-manager-vpnc/network-manager-vpnc_1.2.6-3_amd64.deb
--2022-04-28 19:34:27--  http://ftp.it.debian.org/debian/pool/main/n/network-manager-vpnc/network-manager-vpnc_1.2.6-3_amd64.deb
Resolving ftp.it.debian.org (ftp.it.debian.org)... 85.94.199.210, 2001:4b78:2000:1::1
Connecting to ftp.it.debian.org (ftp.it.debian.org)|85.94.199.210|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 125812 (123K) [application/vnd.debian.binary-package]
Saving to: ‘network-manager-vpnc_1.2.6-3_amd64.deb’

network-manager-vpnc_1.2.6-3_am 100%[====================================================>] 122.86K  --.-KB/s    in 0.05s   

2022-04-28 19:34:27 (2.29 MB/s) - ‘network-manager-vpnc_1.2.6-3_amd64.deb’ saved [125812/125812]

mcon@cinderella:/tmp/t$ wget http://ftp.it.debian.org/debian/pool/main/n/network-manager-vpnc/network-manager-vpnc-gnome_1.2.6-3_amd64.deb
--2022-04-28 19:34:56--  http://ftp.it.debian.org/debian/pool/main/n/network-manager-vpnc/network-manager-vpnc-gnome_1.2.6-3_amd64.deb
Resolving ftp.it.debian.org (ftp.it.debian.org)... 85.94.199.210, 2001:4b78:2000:1::1
Connecting to ftp.it.debian.org (ftp.it.debian.org)|85.94.199.210|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 35592 (35K) [application/vnd.debian.binary-package]
Saving to: ‘network-manager-vpnc-gnome_1.2.6-3_amd64.deb’

network-manager-vpnc-gnome_1.2. 100%[====================================================>]  34.76K  --.-KB/s    in 0.02s   

2022-04-28 19:34:56 (1.69 MB/s) - ‘network-manager-vpnc-gnome_1.2.6-3_amd64.deb’ saved [35592/35592]
mcon@cinderella:~$ sudo apt remove --purge network-manager-vpnc network-manager-vpnc-gnome 
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
The following package was automatically installed and is no longer required:
  vpnc
Use 'sudo apt autoremove' to remove it.
The following packages will be REMOVED:
  network-manager-vpnc* network-manager-vpnc-gnome*
0 upgraded, 0 newly installed, 2 to remove and 0 not upgraded.
After this operation, 1,026 kB disk space will be freed.
Do you want to continue? [Y/n] 
(Reading database ... 244048 files and directories currently installed.)
Removing network-manager-vpnc-gnome (1.2.8-3) ...
Removing network-manager-vpnc (1.2.8-3) ...
Processing triggers for dbus (1.14.0-1) ...
mcon@cinderella:~$ sudo dpkg -i /tmp/t/network-manager-vpnc_1.2.6-3_amd64.deb 
Selecting previously unselected package network-manager-vpnc.
(Reading database ... 243969 files and directories currently installed.)
Preparing to unpack .../network-manager-vpnc_1.2.6-3_amd64.deb ...
Unpacking network-manager-vpnc (1.2.6-3) ...
Setting up network-manager-vpnc (1.2.6-3) ...
Processing triggers for dbus (1.14.0-1) ...
mcon@cinderella:~$ sudo dpkg -i /tmp/t/network-manager-vpnc-gnome_1.2.6-3_amd64.deb 
Selecting previously unselected package network-manager-vpnc-gnome.
(Reading database ... 244039 files and directories currently installed.)
Preparing to unpack .../network-manager-vpnc-gnome_1.2.6-3_amd64.deb ...
Unpacking network-manager-vpnc-gnome (1.2.6-3) ...
Setting up network-manager-vpnc-gnome (1.2.6-3) ...
mcon@cinderella:~$

Then, after checking it actually works:

mcon@cinderella:/tmp/t$ sudo apt-mark hold network-manager-vpnc
network-manager-vpnc set on hold.
mcon@cinderella:/tmp/t$ sudo apt-mark hold network-manager-vpnc-gnome
network-manager-vpnc-gnome set on hold.

MANY Thanks to @Stephen

wget rather than configuring the correct snapshot (or testing or stable...) repository prevents any signature-backed validation of the package. — A.B, Apr 28 '22 at 17:59
@A.B: I understand, but I don't know how to use `apt` to select a specific "historic" version (i.e.: not currently considered "current" in any release) taken directly from snapshot.debian.org; info/recipes/pointers welcome. — ZioByte, Apr 28 '22 at 19:58
for the repository syntax https://snapshot.debian.org/ : there are examples on the main page. For finding, find your binary package, select the version you want and go to the directory with this package: part of the URL above will show what to put as repository using the syntax on the main page. — A.B, Apr 28 '22 at 20:48
Thanks @A.B I saw the main page, but it's unclear to me how pin a specific version (as opposed to a specific date); I assume I should be able to use `apt`'s `=` syntax to chose the specific version; could you give a complete example I could incorporate in my "Update" for the sake of future users? (Hint: you could also write a self-answered question "how to install a specific version of a package in Debian Sid" and I could link it here) TiA! — ZioByte, Apr 29 '22 at 09:29

score 1 · Accepted Answer · answered Apr 28 '22 at 16:54

If you’re using Debian, I doubt the older version was 1.2.7, since that was never uploaded to the archives. Note that for apt’s = syntax, you need to specify full package versions, e.g. “1.2.8-3”.

Regardless, you can find all the versions of a package uploaded to the archives in the last 15 years on snapshot.debian.org; this includes network-manager-vpnc. Download the appropriate package there, install it (using dpkg -i), and then put a hold on it (apt-mark hold network-manager-vpnc) so it doesn’t get upgraded again.

You can configure an apt source for a specific snapshot; see Debian 10 : Upgrade to specific minor release (10.10) for details. You might also find Why do previous versions of Debian packages vanish in the package repositories? (highly relevant for version-controlled system configuration) relevant.

Please also file a bug (reportbug network-manager-vpnc) so that others can be made aware of the regression and hopefully it can be fixed.

Thanks. I did not open a specific bug because I thought it was already reported; it surely was reported for [Ubuntu](https://bugs.launchpad.net/ubuntu/+source/network-manager-applet/+bug/1968588). I will search for relevant downgrade and update question to reflect solving workaround (if found). — ZioByte, Apr 28 '22 at 17:18
Ah yes, thanks; I’d checked the Debian bug tracker but not Ubuntu’s. — Stephen Kitt, Apr 28 '22 at 18:06

Debian Sid: downgrading a single package to a "previous version"

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