I tried with security.debian.org [1] which does not have a d-i section
for lenny, but I don't get any errors (even without --dry-run). So it
seems that non-existing sections are already skipped without any problems.
Also note that if none of the dists that are being mirrored have a d-i
section, then the easiest solution is to simply not specify it.
[1] debmirror --dry-run --host=security.debian.org --method=http \
--dist=lenny/updates --root=debian-security \
--section=main,main/debian-installer \
--nosource --verbose --ignore-release tmp
Mirroring to tmp from http://security.debian.org/debian-security/
Arches: i386
Dists: lenny/updates
Sections: main,main/debian-installer
Pdiff mode: use
Will clean up AFTER mirroring.
Attempting to get lock, this might take 2 minutes before it fails.
Get Release files.
[0%] Getting: dists/lenny/updates/Release... ok
[0%] Getting: dists/lenny/updates/Release.gpg... ok
gpgv: Signature made Tue 11 May 2010 09:27:15 PM CEST using RSA key ID 55BE302B
gpgv: Good signature from "Debian Archive Automatic Signing Key (5.0/lenny) <ftpmaster@debian.org>"
Get Packages and Sources files and other miscellany.
dists/lenny/updates/main/binary-i386/Packages.gz needs fetch
[ 2%] Getting: dists/lenny/updates/main/binary-i386/Packages.gz... ok
dists/lenny/updates/main/binary-i386/Release needs fetch
[100%] Getting: dists/lenny/updates/main/binary-i386/Release... ok
Parse Packages and Sources files and add to the file list everything therein.
[...]