Hi, > [ 215.199357] loop0: rw=524288, want=1903876, limit=1899264 This looks much like a truncated ISO image. (For what reason ever.) There are at least 4612 blocks = ~ 9 MiB missing. In the original message of https://issues.guix.info/issue/33639 the the minimum missing size is about 5 MiB. Please consider local reasons for truncated ISO images. In the following i will concentrate on a potential program bug. > [...] running Xorriso 1.5.0 built for i686 [...] I/O errors [...] > Using the exact same build process for x86_64 leads to valid ISO images. Well, this would explain why 1.5.0 passed a regression test on my 64 bit system with repacking about 200 ISOs, mounting them, and comparing them with the monted original ISOs. I currently lack of opportunities to build 32 bit xorriso. Is there such a damaged ISO available for download ? How much effort would it be to create a Guix installation for building xorriso, running your ISO production, and possibly running xorriso under gdb ? (Something for a run like qemu-system-i386 \ -enable-kvm \ -nographic \ -m 512 \ -net nic \ -net user,hostfwd=tcp::5555-:22 \ -hda guix_on_qemu.img with the opportunity to login from the host machine via SSH. ) What do you get from this xorriso inspection run on a damaged ISO ? (I tested it with the ISO from https://www.gnu.org/software/guix/download/): xorriso -indev guixsd-install-0.15.0.i686-linux.iso \ -find / -sort_lba -exec report_lba -- \ >/tmp/xorriso_indev_find.txt 2>&1 In a preliminary test with guixsd-install-0.15.0.i686-linux.iso i get in /tmp/xorriso_indev_find.txt : ... Media summary: 1 session, 454094 data blocks, 887m data, 384g free ... Report layout: xt , Startlba , Blocks , Filesize , ISO image path File data lba: 0 , 8527 , 1440 , 2949120 , '/efi.img' ... many other files ... File data lba: 0 , 453781 , 122 , 249856 , '/var/guix/db/db.sqlite' The ISO image file size is 929984512 bytes = 454094 blocks. The image by its inner size counter also claims 454094 blocks. The data file with the highest storage address ends before block 453781 + 122 = 453903. That's 191 blocks before the image end. Padding and GPT backup follow. (The data block size is 2048 bytes.) So this image looks ok. Let's read all its files: # mount guixsd-install-0.15.0.i686-linux.iso /mnt/iso mount: /dev/loop0 is write-protected, mounting read-only $ tar cf - /mnt/iso | wc tar: Removing leading `/' from member names 7116387 35887498 1042391040 $ No i/o error. Unrelated observation: xorriso command -pvd_info reports that the ISO was made with xorriso-1.4.8 with Creation Time: 1970010119010649 This means "1 Jan 1970 19:01:06". Something seems to be wrong with the system clock of the producer machine. Have a nice day :) Thomas