PsExec

PsExec is a command-line tool that lets you execute processes on remote systems and redirect console applications' output to the local system so that these applications appear to be running locally. You can download PsExec for free from the Sysinternals Web site (http://www.sysinternals.com). Here are some advanced tips and tricks to help you leverage the full potential of PsExec as a systems management utility.

The PsTools Suite
PsExec is a member of Sysinternals' PsTools suite, which contains 11 tools. To be in the suite, tools must conform to a set of specifications that includes supporting Windows NT 4.0 and later, being a console application, and having the ability to work on the local system as well as on a remote one. PsTools utilities require no manual installation of software on the remote system, and they let you specify alternative credentials to access the remote system.

Incidentally, the reason that the suite is named PsTools and that all the member tools have Ps as a prefix to their name is that the first tool I developed that satisfied the listed criteria was PsList, a program that lists running processes. I named the tool after the ps utility that performs the same function on UNIX systems.

As with many of the tools in the PsTools suite, PsExec's ability to run processes remotely requires that both the local and remote computers have file and print sharing (i.e., the Workstation and Server services) enabled and that the default Admin$ share (a hidden share that maps to the \windows directory) is defined on the remote system. The reasons for these requirements will become clear later when I describe how PsExec works.

PsExec
PsExec's ability to run processes remotely with no manual installation of software on the remote system makes deployment easy. However, if PsExec were only able to launch a program on a remote system, its usefulness would be limited. PsExec's ability to redirect the input and output of console applications is what makes the tool a versatile systems management utility. Figure 1 shows PsExec's command-line options and gives a hint as to its capabilities. Many Windows administrative console tools can run only on a local machine. PsExec lets you remote-enable any of them. For example, PsExec lets Ipconfig, the Windows utility that displays the TCP/IP configuration for a system's network adapters, show a remote system's configuration. A sample command for that use is

psexec \\remote ipconfig

where remote is the name or IP address of the system you want to query. You'll see Ipconfig's output as if you had run Ipconfig on the local machine.

If you don't specify the path of the program you want to execute, PsExec looks in the \windows\system32 directory of the remote system. If you know that the program isn't in that directory, enter its full path on the remote system; if it's an executable on the local system that you want to execute on the remote system, specify the -c switch and the file's local path. The -c switch directs PsExec to copy the specified executable to the remote system for execution and delete the executable from the remote system when the program has finished running.

An even more powerful use of PsExec's console-redirection capability is to run a command prompt on a remote system as if the command prompt were running locally. This use of PsExec is similar to running a Telnet client on the local machine and connecting to a Telnet service on the remote machine, but you don't need to have the Telnet service, or any other special service, running on the remote system. Simply execute the command:

psexec \\remote cmd

If you want to execute one console command on the remote system, pass the command prompt the /c switch followed by the command you want to execute. For example, the command

psexec \\remote cmd /c ver

displays the Windows version number of the remote system on the local machine's console.

Another popular use of PsExec is to deploy hotfixes or other patches that support a noninteractive interface across your network. To make this task even easier, PsExec takes multiple computer names, the name of a text file containing a list of computer names, or the special name of \\* that results in an enumeration of all the computers in the current domain. For instance, to execute the Microsoft MyDoom removal tool on computers named Remote and Remote1 and log the exit status of the cleanup to a file, you could use the command

psexec \\remote,remote1
	-c doomcln.exe
	-s 2> results.log

Upon exit, a process specifies an integer that the process's parent process can read. Programs often use the exit code to report the success or failure of their execution. Whenever a process executed with PsExec is completed, PsExec displays the process's exit code and returns the exit code as its own exit code. You should test a program's behavior or check its documentation to determine what that program's specific error codes mean, but an exit code of 0 typically means success. The -s switch specifies that PsExec should execute the command under the System account. I'll discuss this option more in a moment.

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