salt: hanging at Executing command 'apt-get -q update'

Hi, recently I tried using saltstack on my embedded ARM device, but the process hangs at

Executing command 'apt-get -q update' in directory '/root'

then I tried using:

sudo salt-call --local pkg.upgrade -l all

but with the same result:

[DEBUG   ] Reading configuration from /etc/salt/minion
[DEBUG   ] Using cached minion ID from /etc/salt/minion_id: xbian.private
[TRACE   ] None of the required configuration sections, 'logstash_udp_handler' and 'logstash_zmq_handler', were found the in the configuration. Not loading the Logstash logging handlers module.
[DEBUG   ] Configuration file path: /etc/salt/minion
[TRACE   ] Trying pysss.getgrouplist for 'root'
[TRACE   ] Trying generic group list for 'root'
[TRACE   ] Group list for user 'root': []
[DEBUG   ] Reading configuration from /etc/salt/minion
[TRACE   ] 'dmidecode' could not be found in the following search path: ['/usr/local/sbin', '/usr/local/bin', '/usr/sbin', '/usr/bin', '/sbin', '/bin']
[TRACE   ] 'smbios' could not be found in the following search path: ['/usr/local/sbin', '/usr/local/bin', '/usr/sbin', '/usr/bin', '/sbin', '/bin']
[DEBUG   ] The `dmidecode` binary is not available on the system. GPU grains will not be available.
[TRACE   ] 'dmidecode' could not be found in the following search path: ['/usr/local/sbin', '/usr/local/bin', '/usr/sbin', '/usr/bin', '/sbin', '/bin']
[TRACE   ] Device sda does not report itself as an SSD
[TRACE   ] Device mmcblk0 reports itself as an SSD
[DEBUG   ] LazyLoaded jinja.render
[DEBUG   ] LazyLoaded yaml.render
[DEBUG   ] LazyLoaded jinja.render
[DEBUG   ] LazyLoaded yaml.render
[TRACE   ] Loaded aptpkg as virtual pkg
[DEBUG   ] LazyLoaded pkg.upgrade
[TRACE   ] Loaded cmdmod as virtual cmd
[DEBUG   ] LazyLoaded cmd.run_all
[INFO    ] Executing command 'apt-get -q update' in directory '/root'

but executing this command:

sudo apt-get -q update

manually works without any problem

here is the version info:

               Salt: 2015.5.0
                Python: 2.7.9 (default, Mar  1 2015, 13:48:22)
                Jinja2: 2.7.3
              M2Crypto: 0.21.1
        msgpack-python: 0.4.2
          msgpack-pure: Not Installed
              pycrypto: 2.6.1
               libnacl: Not Installed
                PyYAML: 3.11
                 ioflo: Not Installed
                 PyZMQ: 14.4.0
                  RAET: Not Installed
                   ZMQ: 4.0.5
                  Mako: Not Installed
 Debian source package: 2015.5.0+ds-1~bpo8+1