Linux remote administration on Android and iOS


As elegant as a console or a graphical login session can be, a system administrator often just needs answers to the usual questions. How full are the file systems, how many users are logged on to the system, and how long has it actually been running?

If you have not organized your systems in a comprehensive monitoring system like Nagios, you might well appreciate a tool such as Cura-SysAdmin [14] (Figure 7), which is only available for Android. Cura answers these and other questions and also includes a rather rudimentary terminal emulator, the Nmap port scanner, and a logfile viewer, providing pre-configured access to the main system logs in /var/log, which you can even store on the Android device.

Figure 7: Cura-SysAdmin shows the most important monitoring data in an Android view.

An inelegant, optional feature of Cura prevents installation on Android devices that do not have a SIM card. Cura implements an option for remotely deleting the Cura database and for sending text/email messages with the current positional data in case of loss; thus, GSM connectivity is imperative.

Managing Files with ES File Explorer

Users looking for a file manager that is also suitable for use on a network will inevitably end up knocking at the door of ES File Explorer [15]. Besides its functionality as an easy-to-use file manager with support for ZIP and RAR archives, it offers an integrated file viewer that can handle most formats, and a search function to help you find all files of a certain type on the device, for example.

In the world beyond your own, device-wide protocol support becomes very important. ES File Explorer supports access via FTP, SFTP, FTPS, WebDAV, and CIFS. If you store your data in the cloud, you can open a connection to Dropbox, SkyDrive, GDrive, and Amazon S3, among others. In heterogeneous environments, in particular, it would be delightful to have an implementation of the Network File System (NFS) and the Apple Filing Protocol (AFP), but that is rare on mobile devices.

iOS users who want to access network shares and cloud resources turn to tools such as the commercial FileExplorer [16], whose free version (FileExplorer Free [17]) remains limited to one target.

Scanning and Sniffing Your Network

Once you have had enough mobile management and want to check out your own network, the versatile Fing [18] (Figure 8) is good for starters. It works on both Android and iOS and scans all the devices registered on the network, revealing the hostname, IP and MAC addresses, and, if possible, the manufacturer of the network device. The concise list can help you quickly determine the IP address of a forgotten device or check to see whether a machine is online and then discover which DHCP address it was assigned by the server. The lists can be stored either on the device or in the manufacturer's cloud, Fingbox, which is a commercial operation.

Figure 8: (Left) Fing lists the services running on a scanned system and the associated access programs; (center) Fing shows information about the current WiFi network and determines the ISP; (right) the password manager KeePassDroid acts as a mobile wallet for passwords.

Tapping an entry starts a port scan on the corresponding target. If you find open services, you can run the appropriate apps for the service right away. The app suggests ConnectBot for SSH and AndFTP [19] for SCP and SFTP. Also, direct access to CIFS connections via AndSMB [20] is preconfigured, as is access to any web interfaces you discover.

Additionally, you can run a number of classic network tools (e.g., Telnet, Ping, and Traceroute) against a host. The ability to wake up a system using Wake-on-LAN (WoL) is also in place. If you want to wake a device that is not on your list, you can do so via the global settings menu. This is also where you can perform DNS lookups or run pings and traceroutes against any computer.

Fing is also useful as a security tool. For example, you can find out whether a router on the hotel WLAN uses client isolation (i.e., whether the individual devices can see each other) by running Fing. If you see other systems and services, you should transfer unencrypted data only after careful consideration.

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