Strace and debugging commands help

I've like to know more in general about how to run strace and debug errors in the general.

Specifically, my device was having issues and I saw errors like these in the logs.

Code:

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2016-03-15 02:46:37,ERROR,QC-QMI,com.android.sdm.plugins.diagmon,linux_qmi_qmux _io_wake_unlock: Err in writing wakelock=qmuxd_port_wl_0, error [1: eek: operation not permitted]

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I flashed factory images for mhc19i. With my only mods being twrp 3.0.0.1 and su 2.67, I'm seeing a lot of these qmuxd errors.

Code:

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03-26 17:37:09.597  512  512 E QC-QMI  : qmuxd: RX on fd=16 returned error=0 errno[2:No such file or directory]

03-26 17:37:09.598  512  512 E QC-QMI  : QMUX qmux_client_id=4a not found in qmux client list, unable to remove

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I'm really curious what is going on with this and I'd like to learn how to dig deeper. I tried running strace on the pid, but it wouldn't find a process using the number from logcat and qmuxd wasn't listed when I ran ps. I tried stop stopping ril-daemon and qmuxd and using strace to run qmuxd as directed in an old post.

Code:

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1|u0_a105@angler:/ $ strace -ff -v -o /sdcard/straceqmuxd -s 256 /system/bin/qmuxd
strace: Can't stat '/system/bin/qmuxd': Permission denied
1|u0_a105@angler:/ $ su strace -ff -v -o /sdcard/straceqmuxd -s 256 /system/bin/qmuxd
sush: sush: - : unknown option

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Can anyone point out where I'm going wrong or where I can learn how to troubleshoot these things?

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