Hi, I'm working on getting a cluster with xCAT 2.9.1 and CentOS 7.1 ready. There is a basic installation, but there is one blunt reason why the default packaging of stateless rootimgs with cpio is not working for us:
We live in a world with more accounts than 16 bit can accomodate. Hence, there are system-relevant accounts with UIDs high up in the 32 bit range to avoid conflict with ID ranges for ordinary users (managed by a directory service). This means that cpio has trouble packing up the thing. My first guess about it not handling 32 bit UIDs wasn't the point, actually, but this was: cpio: var/log/lastlog: field width not sufficient for storing file size Funny, eh? var/log/lastlog is a sparse file of 51 GiB because of some large UIDs. Now, I was able to fix that by ln -sf /dev/null var/log/lastlog , probably a sensible move in any case, but actually I would really would like to be able that one alternative to cpio that there is in xCAT: squashfs. That would free up about half the RAM the rootfs needs, perhaps more when using xz compression (one step after another). That is not supported on CentOS right now, as it seems, but I fail to see a strong reason. The trouble is that, on boot, the initrd tries to mount squashfs with an aufs overlay. Aufs is not present anymore, but overlayfs is (just modprobe overlay, it's already in the initrd). So, I figure that I just need to modify some lines in a script to mount overlayfs instead of aufs. I'm not yet clear about which part of xCAT or simply the CentOS host creates initrd-stateless.gz. I guess I could "postprocess" that for now, but I'd like to have packimage (or genimage) do it properly. Where should I properly edit the code to work with squashfs+overlayfs? Regards, Thomas -- Dr. Thomas Orgis Universität Hamburg RRZ / Zentrale Dienste / HPC Schlüterstr. 70 20146 Hamburg Tel.: 040/42838 8826 Fax: 040/428 38 6270
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