Firstly, try running pacman -Syy, then try to install sudo again.

Check that the repositories are uncommented in /etc/pacman.conf.

Or your mirrorlist might be outdated: Generate a current list of mirrors and copy it to /etc/pacman.d/mirrorlist

Quoting from this relevant forum thread:

You can:

• pick another mirror
• try using an http mirror, not an ftp one (pick http mirror from the mirrorlist). Alternatively you can manually download the databases

wget > ftp://mirror.csclub.uwaterloo.ca/archlinux/community/os/x86_64/community.db > wget > ftp://mirror.csclub.uwaterloo.ca/archlinux/extra/os/x86_64/extra.db 

move them to /var/lib/pacman/sync/ and run 'pacman -Syu' again.

If you find any *.part files in /var/lib/pacman/sync/ e.g. /var/lib/pacman/sync/core.db.part - remove them.

To prevent having problems like these it is critical to understand pacman. To learn more about using pacman, see the ArchWiki pacman article, and consult man pacman.

Firstly, try running pacman -Syy, then try to install sudo again.

Check that the repositories are uncommented in /etc/pacman.conf.

Or your mirrorlist might be outdated: Generate a current list of mirrors and copy it to /etc/pacman.d/mirrorlist

Quoting from this relevant forum thread:

You can:

• pick another mirror

• try using an http mirror, not an ftp one (pick http mirror from the mirrorlist).

• Alternatively you can manually download the databases with:

   wget ftp://mirror.csclub.uwaterloo.ca/archlinux/community/os/x86_64/community.db wget ftp://mirror.csclub.uwaterloo.ca/archlinux/extra/os/x86_64/extra.db 

  move them to /var/lib/pacman/sync/ and run 'pacman -Syu' again. If you find any *.part files in /var/lib/pacman/sync/ e.g. /var/lib/pacman/sync/core.db.part - remove them.

To prevent having problems like these it is critical to understand pacman. To learn more about using pacman, see the ArchWiki pacman article, and consult man pacman.