setup-storage: wait for LV device node before using it#139
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After lvcreate returns, the kernel has created the underlying /dev/dm-N device, but the friendly-name symlinks /dev/<vg>/<lv> (and /dev/mapper/<vg>-<lv>) are only created asynchronously once udev processes the corresponding uevent. setup-storage already calls "udevadm settle" before every command, but that relies on a reachable, responsive udev daemon and can return prematurely or be a no-op when udev is slow or unreachable -- e.g. in privileged containers sharing the host's /dev (see rancher/os#838) -- which leads to intermittent "mkfs.ext4: No such file or directory" failures. Add wait_for_device(), a small bounded poll loop for the device node itself, and slot it into the LV creation command chain between lvcreate and anything that consumes /dev/<vg>/<lv> (mkfs, resize, ...). This is environment-agnostic and catches the case where udevadm settle alone is not sufficient.
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After lvcreate returns, the kernel has created the underlying
/dev/dm-Ndevice, but the friendly-name symlinks/dev/<vg>/<lv>(and/dev/mapper/<vg>-<lv>) are only created asynchronously once udev processes the corresponding uevent. setup-storage already calls "udevadm settle" before every command, but that relies on a reachable, responsive udev daemon and can return prematurely or be a no-op when udev is slow or unreachable -- e.g. in privileged containers sharing the host's /dev (see rancher/os#838) -- which leads to intermittent "mkfs.ext4: No such file or directory" failures.Add wait_for_device(), a small bounded poll loop for the device node itself, and slot it into the LV creation command chain between lvcreate and anything that consumes /
dev/<vg>/<lv>(mkfs, resize, ...). This is environment-agnostic and catches the case where udevadm settle alone is not sufficient.