In /logs/firmware/unblob_extracted/firmware_extract/DIR-600_fw_revb5_214b01_ALL_de_20130122/dir600b_v2.14_d1mg.bin_extract/1179788-3612812.squashfs_v4_le_extract/etc/init0.d/S80telnetd.sh line 2:

echo [$0]: $1 ... > /dev/console

      ^-- SC2086 (info): Double quote to prevent globbing and word splitting.

           ^-- SC2086 (info): Double quote to prevent globbing and word splitting.

Did you mean:

echo ["$0"]: "$1" ... > /dev/console

In /logs/firmware/unblob_extracted/firmware_extract/DIR-600_fw_revb5_214b01_ALL_de_20130122/dir600b_v2.14_d1mg.bin_extract/1179788-3612812.squashfs_v4_le_extract/etc/init0.d/S80telnetd.sh line 5:

		image_sign=`cat /etc/config/image_sign`

                           ^--------------------------^ SC2006 (style): Use $(...) notation instead of legacy backticks `...`.

Did you mean:

		image_sign=$(cat /etc/config/image_sign)

In /logs/firmware/unblob_extracted/firmware_extract/DIR-600_fw_revb5_214b01_ALL_de_20130122/dir600b_v2.14_d1mg.bin_extract/1179788-3612812.squashfs_v4_le_extract/etc/init0.d/S80telnetd.sh line 6:

		telnetd -l /usr/sbin/login -u Alphanetworks:$image_sign -i br0 &

                                                            ^---------^ SC2086 (info): Double quote to prevent globbing and word splitting.

Did you mean:

		telnetd -l /usr/sbin/login -u Alphanetworks:"$image_sign" -i br0 &

For more information:

  https://www.shellcheck.net/wiki/SC2086 -- Double quote to prevent globbing ...

  https://www.shellcheck.net/wiki/SC2006 -- Use $(...) notation instead of le...

[*] Source file S80telnetd.sh