System Log In
The next step after establishing a physical connection to the board is logging in. EMAC OE Linux allows login from getty, SSH (Secure Shell) and Telnet. A getty uses the serial connection or console while SSH and Telnet utilize a network connection.
|Warning: Using Telnet will expose all data "in the clear" to everyone in the network you are using. This includes your password and any data you transmit between the system and your computer. EMAC recommends using SSH for all network connections. Telnet should never be used if the system is connected directly to the Internet outside of any firewall or NAT router.|
In addition to the root account, a user account with limited system permissions is also enabled by default. The default login and password are shown in Table 4 below.
|Table 4: Default Login Credentials|
|Note: It is normal to not see any output while typing in a password at a Linux login prompt.|
If you have established a serial connection with the board, the login prompt should be visible in the terminal application on the workstation similar to what is shown below.
EMAC OpenEmbedded Linux 4.0 (stable-2009) Some code contained within Copyright 2008-2011 EMAC, Inc. emac 2009-stable emac-oe ttyS0 emac-oe login:
For an SSH connection, you will need an SSH client application. An SSH client is included by default on most desktop Linux distributions and other operating systems, but is not included on Windows. EMAC recommends using PuTTY for an SSH client on Windows workstations.
SSH uses key pairs to authenticate identity and perform encryption. If the remote host's key is not recognized in the SSH known hosts list or if it changes, the SSH client will print a warning and require confirmation to continue. If this is the first connection attempt to this system, you will most likely see a message about the host key not being recognized similar to the following:
The authenticity of host '[10.0.2.41] ([10.0.2.41])' can't be established. RSA key fingerprint is 5f:cc:f3:25:9d:37:89:bd:94:fc:74:a0:eb:55:a9:6a. Are you sure you want to continue connecting (yes/no)? yes Warning: Permanently added '[10.0.2.41]' (RSA) to the list of known hosts.
Any SSH protocol based command can generate this message.
 Logging In
The command line SSH client syntax to log in to a system is
ssh user@host. For example, to log in as root to a system with the IP address 10.0.2.41, you would use the following command:
developer@ldc:~$ ssh firstname.lastname@example.org email@example.com's password: root@emac-oe:~#
To connect to the system using PuTTY under Windows, follow the steps outlined in the PuTTY documentation. PuTTY will also warn if the host key is not recognized in a way similar to the SSH command line client under Linux as described above.
 Transferring Files
The command line syntax for transferring a file using the SSH protocol is
scp file user@host:/directory. SCP or Secure Copy is a way of securely transferring files between a local and remote host. For example, to send the file example.text to the
/home directory of a system with the IP address 10.0.2.41, enter the following command:
developer@ldc:~# scp example.text firstname.lastname@example.org:/home
Be aware that this copy operation will fail if the filesystem on the remote machine is mounted read-only, which is the default on most EMAC systems.
 Remote Execution
SSH can also be used to execute programs on remote systems without logging in. The syntax for SSH remote execution is
ssh user@host "my_command -args file". For example, to run the program hello_world with the -hi flags on a system with the IP address of 10.0.2.41, enter the following command:
developer@ldc:~# ssh email@example.com "hello_world -hi"
 Next Steps
After you have logged into the system, user accounts may be configured.