Hello guys,

Fresh user of your very good distro, I'm experiencing this recent problem when upgrading the OS :

:: Synchronisation des bases de données de paquets…
core est à jour
main est à jour 0,0 B 0,00 B/s 00:00 [c o o o o o o o o o ] 0%
apps est à jour 0,0 B 0,00 B/s 00:00 [c o o o o o o o o o ] 0%
:: Début de la mise à jour complète du système…
erreur : l’ouverture du fichier /var/lib/pacman/sync/core.db a échoué : Unrecognizedchive format
erreur : l’ouverture du fichier /var/lib/pacman/sync/main.db a échoué : Unrecognized archive format
erreur : l’ouverture du fichier /var/lib/pacman/sync/apps.db a échoué : Unrecognized archive format
I have removed the /var/lib/pacman/sync/ directory and so make a pacman -Syy but no positive result.
Any idea to correct this ?

I think this is just that the mirrors are not synced at the moment. Depends what mirrors you are trying to connect to. They are out of sync here at the moment.

Just hit the same issue with a fresh server install (from test ISO).
The default mirror has some corrupted database files right now. I will be moving packages soon which might fix the issue, but I will need to contact the mirror owner to see if he can correct.
In the meantime, best option is to open the mirrorlist:

kate /etc/pacman.d/mirrorlist

and comment out the redcore (first) mirror. Make sure your preferred (closest most often) is the first listed in mirrorlist.
After editing the mirrorlist, you will have to make sure the corrupted database files are no longer in /var/lib/pacman/sync/:

sudo rm /var/lib/pacman/sync/core.db
sudo rm /var/lib/pacman/sync/main.db
sudo rm /var/lib/pacman/sync/apps.db

To see the status of all mirrors:
https://kaosx.us/packages/mirrors.php

@demm all is ok with commenting out the main server in the mirrorlist and removing the *.db in /var/lib/pacman/sync/ thanks a lot.

The owner of the mirror has responded, and there are major issues with it. The server is still up, but the domain-name is not.
pacman-mirrorlist has been updated to use a new default mirror:
https://github.com/KaOSx/core/commit/19c5ce34a072dc7846dd4f3ed21282113925ba49#diff-0d8fb9a3fbba1185cd2162e7f0f842cf06cfca744b13323b67a4c3a046b61efdL6
I will move the new package today, so you can pacmerge to get the corrections too.
Leaves all effected to still having to manually remove the corrupted .db files though, see post #3.

    5 months later

    demm when youe refered at "comment out" , What do you mean?

      Place a # in front of it.