Impersonation on Linux and UNIX systems

The su command (as used by IBM® UrbanCode™ Deploy) enables a user to start a shell as another user (process steps can be considered individual shells).

When you configure a process step (see Processes), you can tell IBM UrbanCode Deploy to use impersonation for the step. By default, su is used but you can use sudo instead. To configure impersonation, you supply the user name that is required by the target host. When the impersonation-configured process step runs, the su or sudo command runs the step as the impersonated user. Each step that needs user impersonation must be configured independently.

Before sudo can be used, impersonation privileges must be defined in the /etc/sudoers file. When you configure sudoers, ensure that the impersonating user does not need to supply a password. Typically, you would configure the /etc/sudoers file like the following example:

Defaults:X !requiretty

X ALL=(Y) NOPASSWD: ALL

where X and Y are user names. Configured this way, user X can run any command as user Y without supplying a password.

Note: The impersonated user must have read and execute access to the agent working directory.

As an alternative to configuring sudoers, in some cases you can configure the PAM via the module pam_wheel.so to allow certain users to log in without specifying a password. In this case, add users to a specific wheel group and edit the PAM configuration allow users in this group to run commands as though they were the root user.

su and sudo maintain a record in the system logs of all of their activity. su can be used without configuring the sudoers file. For information about su/sudo, see the UNIX or Linux documentation.

Note: For UNIX or Linux agents, the password option is ignored.

To customize the su and sudo commands, you can set the following properties on the agent, in the installed.properties file:

Table 1. Agent properties for the su and sudo commands
Property	Default value	Description
com.urbancode.shell.impersonation.unix.sudoFormat	`%s -n -u %u %c`	Syntax of the sudo command
com.urbancode.shell.impersonation.unix.sudoGroupFormat	`%s -n -u %u -g %g %c`	Syntax of the sudo command when a group is specified
com.urbancode.shell.impersonation.unix.suFormat	`%s - %u -c %c`	Syntax of the su command

Tip: To set these properties on new agents, create a generic process that updates the installed.properties file and run the process on new agents.

You can use the following variables in these properties:

Table 2. Variables for the su and sudo commands
Variable	Value
`%s`	The location of the su or sudo executable
`%u`	The user
`%g`	The group
`%c`	The command to run

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