staprun

Sommaire

NAME

staprun - systemtap runtime

SYNOPSIS


staprun [ OPTIONS ] MODULE [ MODULE-OPTIONS ]

DESCRIPTION

The staprun program is the back-end of the Systemtap tool. It expects a kernel module produced by the front-end stap tool.

Splitting the systemtap tool into a front-end and a back-end allows a user to compile a systemtap script on a development machine that has the kernel debugging information (need to compile the script) and then transfer the resulting kernel module to a production machine that doesn't have any development tools or kernel debugging information installed.

Please refere to stappaths (7) for the version number, or run rpm -q systemtap (fedora/red hat) apt-get -v systemtap (ubuntu)

OPTIONS

The staprun program supports the following options. Any other option prints a list of supported options.
-v
Verbose mode.
-c CMD
Command CMD will be run and the staprun program will exit when CMD does. The '_stp_target' variable will contain the pid for CMD.
-x PID
The '_stp_target' variable will be set to PID.
-o FILE
Send output to FILE. If the module uses bulk mode, the output will be in percpu files FILE_x(FILE_cpux in background and bulk mode) where 'x' is the cpu number. This supports strftime(3) formats for FILE.
-b BUFFER_SIZE
The systemtap module will specify a buffer size. Setting one here will override that value. The value should be an integer between 1 and 4095 which be assumed to be the buffer size in MB. That value will be per-cpu if bulk mode is used.
-L
Load module and start probes, then detach from the module leaving the probes running. The module can be attached to later by using the -A option.
-A
Attach to loaded systemtap module.
-d
Delete a module. Only detached or unused modules the user has permission to access will be deleted. Use "*" (quoted) to delete all unused modules.
-D
Run staprun in background as a daemon and show it's pid.
-S size[,N]
Sets the maximum size of output file and the maximum number of output files. If the size of output file will exceed size , systemtap switches output file to the next file. And if the number of output files exceed N , systemtap removes the oldest output file. You can omit the second argument.
var1=val
Sets the value of global variable var1 to val. Global variables contained within a module are treated as module options and can be set from the staprun command line.

ARGUMENTS

MODULE is either a module path or a module name. If it is a module name, the module will be looked for in the following directory (where 'VERSION' is the output of "uname -r"):
/lib/modules/VERSION/systemtap

Any additional arguments on the command line are passed to the module. One use of these additional module arguments is to set the value of global variables declared within the module.

$ stap -p4 -m mod1 -e 'global var1="foo"; probe begin{printf("%s\n", var1); exit()}'

Running this with an additional module argument:

$ staprun mod1.ko var1="HelloWorld"
HelloWorld

Spaces and exclamation marks currently cannot be passed into global variables this way.

EXAMPLES

See the stapex(3stap) manual page for a collection of sample scripts.

Here is a very basic example of how to use staprun. First, use stap to compile a script. The stap program will report the pathname to the resulting module.

$ stap -p4 -e 'probe begin { printf("Hello World!\n"); exit() }'
/home/user/.systemtap/cache/85/stap_8553d83f78c_265.ko

Run staprun with the pathname to the module as an argument.

$ staprun /home/user/.systemtap/cache/85/stap_8553d83f78c_265.ko
Hello World!

MODULE DETACHING AND ATTACHING

After the staprun program installs a Systemtap kernel module, users can detach from the kernel module and reattach to it later. The -L option loads the module and automatically detaches. Users can also detach from the kernel module interactively by sending the SIGQUIT signal from the keyboard (typically by typing Ctrl-\).

To reattach to a kernel module, the staprun -A option would be used.

FILE SWITCHING BY SIGNAL

After the staprun launched the stapio , users can command it to switch output file to next file when it outputs to file(s) (running staprun with -o option) by sending a SIGUSR2 signal to the stapio process. When it receives SIGUSR2, it will switch output file to new file with suffix .N where N is the sequential number. For example,

$ staprun -o foo ...

outputs trace logs to foo and if it receives SIGUSR2 signal, it switches output to foo.1 file. And receiving SIGUSR2 again, it switches to foo.2 file.

SAFETY AND SECURITY

Systemtap is an administrative tool. It exposes kernel internal data structures and potentially private user information. See the stap(1) manual page for additional information on safety and security.

To increase system security, only the root user and members of the stapdev group can use staprun to insert systemtap modules (or attach to existing ones). Members of the stapusr group can use staprun to insert or remove systemtap modules (or attach to existing systemtap modules) under the following conditions:

•
The module is located in the /lib/modules/VERSION/systemtap directory. This directory must be owned by root and not be world writable.
•
The module has been signed by a trusted signer. Trusted signers are normally systemtap compile servers which sign modules when the --unprivileged option is specified by the client. See the stap-server(8) manual page for a for more information.

FILES

/lib/modules/VERSION/systemtap
If MODULE is a module name, the module will be looked for in this directory. Users who are only in the 'stapusr' group can install modules located in this directory. This directory must be owned by the root user and not be world writable.

SEE ALSO

stap(1), stapprobes(3stap), stapfuncs(3stap), stap-server(8), stapex(3stap)

BUGS

Use the Bugzilla link of the project web page or our mailing list. http://sources.redhat.com/systemtap/, <systemtap@sources.redhat.com>.