On 5/29/24 5:05 PM, Wolfram Sang wrote: > Hi Eric, > > thanks for replying! > >> @Wolfram, what did your actual fstab line look like? I wonder what is actually >> trying to pass auto as a mount option, and why... > > My fstab entry looks like this: > > debugfs /sys/kernel/debug debugfs auto 0 0 > > This happened on an embedded system using busybox 1.33.0. strace is > currently not installed but I can try adding it if that is needed. > > Happy hacking, > > Wolfram > Welp, that looks like it: # strace busybox mount /debugfs-test ... stat("debugfs", 0x7fffc05d3d60) = -1 ENOENT (No such file or directory) mount("debugfs", "/debugfs-test", "debugfs", MS_SILENT, "auto") = -1 EINVAL (Invalid argument) write(2, "mount: mounting debugfs on /debu"..., 66mount: mounting debugfs on /debugfs-test failed: Invalid argument ) = 66 This does not appear to be unique to debugfs: # grep tmp /etc/fstab /dev/loop0 /tmp/xfs xfs auto 0 0 # strace busybox mount /tmp/xfs ... mount("/dev/loop0", "/tmp/xfs", "xfs", MS_SILENT, "auto") = -1 EINVAL (Invalid argument) write(2, "mount: mounting /dev/loop0 on /t"..., 64mount: mounting /dev/loop0 on /tmp/xfs failed: Invalid argument ) = 64 # dmesg | grep auto | tail -n 1 [ 1931.471667] xfs: Unknown parameter 'auto' This looks to me like a busybox flaw, not a debugfs bug (change in unknown argument behavior notwithstanding...) -Eric