The stock system has SELinux in enforcing mode. Check with sestatus.
With SELinux in enforcing mode, you don't have access to certain locations even as the root user.
To disable SELinux, edit /etc/selinux/config then change line SELINUX= to SELINUX=disabled
Reboot, and SELinux should be disabled:
/ # sestatus
SELinux status: disabledNo one wants to lose root access. Things to perserve
- Firmware version. Meaning - disable auto update
- Root telnet
dx entry Oma.DMAccountServerAddress1 is used as the server URL for auto update. Source
Value for stock ATT MR6500 is https://xdm.wireless.att.com:443/oma. The value is stored in NVRAM so flashing a firmware doesn't override it.
To disable auto update, set it to garbage or an empty string:
dx -c Oma.DMAccountServerAddress1 ""Get a static linking build from https://github.com/binary-manu/static-cross-openssh
This is trivial