Hello Cyril, Thanks for looking into this.
> The issue is likely that none of the URLs was fetched successfully, > rather than the last one returning 404. No, I can't confirm this. Normally we use a http proxy during installation/preseeding ( squid-deb-proxy and with "d-i mirror/http/proxy string ..." in preseed config) Therefor when using the "normal" mirror ftp.de.debian.org I can see in the squid logs that the installer request InRelease, Release, Release.gpg, Packages.xz whereas when using snapshot.debian.org it requests InRelease, Release, Release.gpg, Packages.xz, Packages.gz, Packages (which is answered with http status code 404) So Packages.gz, Packages are requested in addition when using snapshot.debian.org. Here is an excerpt of the squid logs: ftp.de.debian.org ============= 1499424363.414 42 195.66.76.23 TCP_MISS/404 615 GET http://ftp.de.debian.org/debian/dists/stretch/InRelease - HIER_DIRECT/141.76.2.4 text/html 1499424363.501 58 195.66.76.23 TCP_REFRESH_UNMODIFIED/200 113783 GET http://ftp.de.debian.org/debian/dists/stretch/Release - HIER_DIRECT/141.76.2.4 - 1499424363.588 52 195.66.76.23 TCP_REFRESH_UNMODIFIED/200 3462 GET http://ftp.de.debian.org/debian/dists/stretch/Release.gpg - HIER_DIRECT/141.76.2.4 - 1499424364.019 153 195.66.76.23 TCP_REFRESH_UNMODIFIED/200 7094856 GET http://ftp.de.debian.org/debian/dists/stretch/main/binary-amd64/Packages.xz - HIER_DIRECT/141.76.2.4 application/x-xz 1499424367.867 0 195.66.76.23 TCP_MEM_HIT/200 28613 GET http://ftp.de.debian.org/debian/pool/main/a/acl/libacl1_2.2.52-3+b1_amd64.deb - HIER_NONE/- application/x-debian-package snapshot.debian.org =================== 1499423482.111 6781 195.66.76.23 TCP_MISS/404 2589 GET http://snapshot.debian.org/archive/debian/20170618T160104Z/dists/stretch/InRelease - HIER_DIRECT/193.62.202.30 text/html 1499423482.143 4 195.66.76.23 TCP_MEM_HIT/200 114207 GET http://snapshot.debian.org/archive/debian/20170618T160104Z/dists/stretch/, - HIER_NONE/- application/octet-stream 1499423482.175 0 195.66.76.23 TCP_MEM_HIT/200 3887 GET http://snapshot.debian.org/archive/debian/20170618T160104Z/dists/stretch/Release.gpg - HIER_NONE/- application/octet-stream 1499423482.638 192 195.66.76.23 TCP_MEM_HIT/200 7095214 GET http://snapshot.debian.org/archive/debian/20170618T160104Z/dists/stretch/main/binary-amd64/Packages.xz - HIER_NONE/- application/octet-stream 1499423483.733 1038 195.66.76.23 TCP_MEM_HIT/200 9497612 GET http://snapshot.debian.org/archive/debian/20170618T160104Z/dists/stretch/main/binary-amd64/Packages.gz - HIER_NONE/- application/octet-stream 1499423489.524 5744 195.66.76.23 TCP_MISS/404 2589 GET http://snapshot.debian.org/archive/debian/20170618T160104Z/dists/stretch/main/binary-amd64/Packages - HIER_DIRECT/193.62.202.30 text/html > snapshot.debian.org is sometimes slow to respond, or can even return an > error (until the backend gets kicked). Can you reproduce the issue every > time? If so, can you wireshark it, just to be sure? Yes, I can reproduce the issue every time. To debar squid-deb-proxy from being the cause of the problem I disabled the "d-i mirror/http/proxy string ..." preseed setting and now it works ! I tried several times without http proxy and each time it succeeded to install from snapshot.debian.org. So it looks like squid-deb-proxy is the problem and not Debootstrap ! The strange thing is that squid-deb-proxy works just fine with ftp.de.debian.org but it fails with snapshot.debian.org for stretch (but it used to work with jessie). I believe that something goes wrong with squid while or just after downloading http://snapshot.debian.org/archive/debian/20170618T160104Z/dists/stretch/main/binary-amd64/Packages.gz I also flushed the squid cache but it then again fails at the same point (even on the first run when it gets a TCP_MISS) Thanks
