Provided by: systemtap-server_5.1-4.1_amd64 
NAME
stap-server - systemtap compile server management
SYNOPSIS
[ service ] stap-server { start | stop | restart | condrestart | try-restart | force-reload | status } [
options ]
DESCRIPTION
A systemtap compile server listens for connections from stap clients on a secure SSL network port and
accepts requests to run the stap front end. Each server advertises its presence and configuration on the
local network using mDNS (avahi) allowing for automatic detection by clients.
The stap-server script aims to provide:
• management of systemtap compile servers as a service.
• convenient control over configured servers and individual (ad-hoc) servers.
ARGUMENTS
One of the actions below must be specified:
start Start servers. The specified servers are started. If no server is specified, the configured
servers are started. If no servers are configured, a server for the kernel release and
architecture of the host is started. If a specified server is already started, this action will
be ignored for that server. If a server fails to start, this action fails.
stop Stop server(s). The specified servers are stopped. If no server is specified, all currently
running servers are stopped. If a specified server is not running, this action will be successful
for that server. If a server fails to stop, this action fails.
restart
Stop and restart servers. The specified servers are stopped and restarted. If no server is
specified, all currently running servers are stopped and restarted. If no servers are running,
this action behaves like start.
condrestart
Stop and restart servers. The specified servers are stopped and restarted. If a specified server
is not running, it is not started. If no server is specified, all currently running servers are
stopped and restarted. If no servers are running, none will be started.
try-restart
This action is identical to condrestart.
force-reload
Stop all running servers, reload config files and restart the service as if start was specified.
status Print information about running servers. Information about the specified server(s) will be
printed. If no server is specified, information about all running servers will be printed.
OPTIONS
The following options are used to provide additional configuration and to specify servers to be managed:
-c configfile
This option specifies a global configuration file in addition to the default global configuration
file described below. This file will be processed after the default global configuration file. If
the -c option is specified more than once, the last configuration file specified will be used.
-a architecture
This option specifies the target architecture of the server and is analogous to the -a option of
stap. See the stap(1) manual page for more details. The default architecture is the architecture
of the host.
-r kernel-release
This option specifies a target kernel release of the server and is analogous to the -r option of
stap. See the stap(1) manual page for more details. The default release is that of the currently
running kernel. A server can handle multiple releases by specifying multiple -r flags.
-I path
This option specifies an additional path to be searched by the server(s) for tapsets and is
analogous to the -I option of stap. See the stap(1) manual page for more details.
-R path
This option specifies the location of the systemtap runtime to be used by the server(s) and is
analogous to the -R option of stap. See the stap(1) manual page for more details.
-B options
This option specifies options to be passed to make when building systemtap modules and is
analogous to the -B option of stap. See the stap(1) manual page for more details.
-i This option is a shortcut which specifies a server that handles every release installed in
/lib/modules/.
-n nickname
This option allows the specification of a server configuration by nickname. When -n is specified,
a currently running server with the given nickname will be searched for. If no currently running
server with the given nickname is found, a server configuration with the given nickname will be
searched for in the configuration files for default servers, or the path configured in the global
configuration file or the configuration file specified by the -c option. If a server configuration
for the given nickname is found, the -a, -r, -I, -R, -B and -u options for that server will be
used as if they were specified on the command line. If no configuration with the given nickname is
found, and the action is start (or an action behaving like start (see ARGUMENTS), the server will
be started with the given nickname. If no configuration with the given nickname is found, and the
action is not start (or an action behaving like start), it is an error. If a nickname is not
specified for a server which is being started, its nickname will be its process id.
-p pid This option allows the specification of a server configuration by process id. When -p is
specified, a currently running server with the given process id will be searched for. If no such
server is found, it is an error. If a server with the given process id is found, the -a, -r, -I,
-R, -B and -u options for that server will be used as if they were specified on the command line.
-u user-name
Each systemtap compile server is normally run by the user name stap-server (for the initscript) or
as the user invoking stap-server, unless otherwise configured (see FILES). This option specifies
the user name used to run the server(s). The user name specified must be a member of the group
stap-server.
--log logfile
This option allows the specification of a separate log file for each server. Each --log option is
added to a list which will be applied, in turn, to each server specified. If more servers are
specified than --log options, the default log file (see FILES) will be used for subsequent
servers.
--port port-number
This option allows the specification of a specific network port for each server. Each --port
option is added to a list which will be applied, in turn, to each server specified. If more
servers are specified than --port options, a randomly selected port is used for subsequent
servers.
--ssl certificate-db-path
This option allows the specification of a separate NSS certificate database for each server. Each
--ssl option is added to a list which will be applied, in turn, to each server specified. If more
servers are specified than --ssl options, the default certificate database (see FILES) for
subsequent servers.
--max-threads threads
This option allows the specification of the maximum number of worker threads to handle concurrent
requests. If threads == 0, each request will be handled on the main thread, serially. The default
is the number of available processor cores.
--max-request-size size
This options allows the specification of the maximum size of an uncompressed client request. The
arguement size is specified in bytes. The default is the 50000 bytes.
--max-compressed-request size
This options allows the specification of the maximum size of a compressed client request. The
arguement size is specified in bytes. The default is the 5000 bytes.
CONFIGURATION
Configuration files allow us to:
• specify global configuration of logging, server configuration files, status files and other global
parameters.
• specify which servers are to be started by default.
Global Configuration
The Global Configuration file contains variable assignments used to configure the overall operation of
the service. Each line beginning with a '#' character is ignored. All other lines must be of the form
VARIABLE=VALUE. This is not a shell script. The entire contents of the line after the = will be assigned
as-is to the variable.
The following variables may be assigned:
CONFIG_PATH
Specifies the absolute path of the directory containing the default server configurations.
STAT_PATH
Specifies the absolute path of the running server status directory.
LOG_FILE
Specifies the absolute path of the log file.
STAP_USER
Specifies the userid which will be used to run the server(s) (default: for the initscript
stap-server, otherwise the user running stap-server).
Here is an example of a Global Configuration file:
CONFIG_PATH=~<user>/my-stap-server-configs
LOG_FILE=/tmp/stap-server/log
Individual Server Configuration
Each server configuration file configures a server to be started when no server is specified for the
start action, or an action behaving like the start action (see ARGUMENTS). Each configuration file con‐
tains variable assignments used to configure an individual server.
Each line beginning with a '#' character is ignored. All other lines must be of the form VARIABLE=VALUE.
This is not a shell script. The entire contents of the line after the = will be assigned as-is to the
variable.
Each configuration file must have a filename suffix of .conf. See stappaths(7) for the default location
of these files. This default location can be overridden in the global configuration file using the -c
option (see OPTIONS).
The following variables may be assigned:
ARCH Specifies the target architecture for this server and corresponds to the -a option (see OPTIONS).
If ARCH is not set, the architecture of the host will be used.
RELEASE
Specifies a kernel release for this server and corresponds to the -r option (see OPTIONS). If RE‐
LEASE is not set, the release of the kernel running on the host will be used.
BUILD Specifies options to be passed to the make process used by systemtap to build kernel modules.
This an array variable with each element corresponding to a -B option (see OPTIONS). Using the
form BUILD=STRING clears the array and sets the first element to STRING. Using the form
BUILD+=STRING adds STRING as an additional element to the array.
INCLUDE
Specifies a list of directories to be searched by the server for tapsets. This is an array vari‐
able with each element corresponding to a -I option (see OPTIONS). Using the form INCLUDE=PATH
clears the array and sets the first element to PATH. Using the form INCLUDE+=PATH adds PATH as an
additional element to the array.
RUNTIME
Specifies the directory which contains the systemtap runtime code to be used by this server and
corresponds to the -R option (see OPTIONS).
USER Specifies the user name to be used to run this server and corresponds to the -u option (see OP‐
TIONS).
NICKNAME
Specifies the nickname to be used to refer to this server and corresponds to the -n option (see
OPTIONS).
LOG Specifies the location of the log file to be used by this server and corresponds to the --log op‐
tion (see OPTIONS).
PORT Specifies the network port to be used by this server and corresponds to the --port option (see OP‐
TIONS).
SSL Specifies the location of the NSS certificate database to be used by this server and corresponds
to the --ssl option (see OPTIONS).
MAXTHREADS
Specifies the maximum number of worker threads to handle concurrent requests to be used by this
server and corresponds to the --max-threads option (see OPTIONS).
MAXREQSIZE
Specifies the maximum size of an uncompressed client request, to be used by this server and corre‐
spnds to the --max-request-size option (see OPTIONS).
MAXCOMPRESSEDREQ
Specifies the maximum size of an compressed client request, to be used by this server and corresp‐
nds to the --max-compressed-request option (see OPTIONS).
Here is an example of a server configuration file:
ARCH=
USER=
RELEASE=
NICKNAME=native
By keeping the ARCH, USER, and RELEASE fields blank, they will default to the current arch and release
and use the default user.
A more specific example:
ARCH=i386
RELEASE=2.6.18-128.el5
PORT=5001
LOG=/path/to/log/file
And here is a more complicated example:
USER=serveruser
RELEASE=/kernels/2.6.18-92.1.18.el5/build
INCLUDE=/mytapsets
INCLUDE+=/yourtapsets
BUILD='VARIABLE1=VALUE1 VARIABLE2=VALUE2'
DEFINE=STP_MAXMEMORY=1024
DEFINE+=DEBUG_TRANS
RUNTIME=/myruntime
NICKNAME=my-server
SSL=/path/to/NSS/certificate/database
SERVER AUTHENTICATION
The security of the SSL network connection between the client and server depends on the proper management
of server certificates.
The trustworthiness of a given systemtap compile server can not be determined automatically without a
trusted certificate authority issuing systemtap compile server certificates. This is not practical in
everyday use and so, clients must authenticate servers against their own database of trusted server cer‐
tificates. In this context, establishing a given server as trusted by a given client means adding that
server's certificate to the client's database of trusted servers.
For the stap-server initscript, on the local host, this is handled automatically. When the system‐
tap-server package is installed, the server's certificate for the default user (stap-server) is automati‐
cally generated and installed. This means that servers started by the stap-server initscript, with the
default user, are automatically trusted by clients on the local host, both as an SSL peer and as a sys‐
temtap module signer.
Furthermore, when stap is invoked by an unprivileged user (not root, not a member of the group stapdev,
but a member of the group stapusr and possibly the group stapsys), the options --use-server and --privi‐
lege are automatically added to the specified options. This means that unprivileged users on the local
host can use a server on the local host in unprivileged mode with no further setup or options required.
Normal users (those in none of the SystemTap groups) can also use compile-servers through the --use-serv‐
er and --privilege options. But they will of course be unable to load the module (the -p4 option can be
used to stop short of loading).
In order to use a server running on another host, that server's certificate must be installed on the
client's host. See the --trust-servers option in the stap(1) manual page for more details and README.un‐
privileged in the systemtap sources for more details.
EXAMPLES
See the stapex(3stap) manual page for a collection of sample systemtap scripts.
To start the configured servers, or the default server, if none are configured:
$ [ service ] stap-server start
To start a server that handles all kernel versions installed in /lib/modules:
$ [ service ] stap-server start -i
To obtain information about the running server(s):
$ [ service ] stap-server status
To start a server like another one, except targeting a different architecture, by referencing the first
server's nickname:
$ [ service ] stap-server start -n NICKNAME -a ARCH
To start a server for a kernel release not installed (cross-compiling)
$ [ service ] stap-server start -a ARCH -r /BUILDDIR
To stop one of the servers by referencing its process id (obtained by running stap-server status):
$ [ service ] stap-server stop -p PID
To run a script using a compile server:
$ stap SCRIPT --use-server
To run a script as an unprivileged user using a compile server:
$ stap SCRIPT
To stop all running servers:
$ [ service ] stap-server stop
To restart servers after a global configuration change and/or when default servers have been added,
changed, or removed:
$ [ service ] stap-server force-reload
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.
As a network server, stap-server should be activated with care in order to limit the potential effects of
bugs or mischevious users. Consider the following prophylactic measures.
1 Run stap-server as an unprivileged user, never as root.
When invoked as a service (i.e. service stap-server ...), each server is run, by default, as the
user stap-server. When invoked directly (i.e. stap-server ...), each server is run, by default,
as the invoking user. In each case, another user may be selected by using the -u option on invoca‐
tion, by specifying STAP_USER=username in the global configuration file or by specifying
USER=username in an individual server configuration file. The invoking user must have authority to
run processes as another user. See CONFIGURATION.
The selected user must have write access to the server log file. The location of the server log
file may be changed by setting LOG_FILE=path in the global configuration file. See CONFIGURATION.
The selected user must have read/write access to the directory containing the server status files.
The location of the server status files may be changed by setting STAT_PATH=path in the global
configuration file. See CONFIGURATION.
The selected user must have read/write access to the uprobes.ko build directory and its files.
Neither form of stap-server will run if the selected user is root.
2 Run stap-server requests with resource limits that impose maximum cpu time, file size, memory con‐
sumption, in order to bound the effects of processing excessively large or bogus inputs.
When the user running the server is stap-server, each server request is run with limits specified
in ~stap-server/.systemtap/rc otherwise, no limits are imposed.
3 Run stap-server with a TMPDIR environment variable that points to a separate and/or quota-enforced
directory, in order to prevent filling up of important filesystems.
The default TMPDIR is /tmp/.
4 Activate network firewalls to limit stap client connections to relatively trustworthy networks.
For automatic selection of servers by clients, avahi must be installed on both the server and
client hosts and mDNS messages must be allowed through the firewall.
The systemtap compile server and its related utilities use the Secure Socket Layer (SSL) as implemented
by Network Security Services (NSS) for network security. NSS is also used for the generation and manage‐
ment of certificates. The related certificate databases must be protected in order to maintain the secu‐
rity of the system. Use of the utilities provided will help to ensure that the proper protection is
maintained. The systemtap client will check for proper access permissions before making use of any cer‐
tificate database.
FILES
Important files and their corresponding paths can be located in the
stappaths (7) manual page.
SEE ALSO
stap(1),
staprun(8),
stapprobes(3stap),
stappaths(7),
stapex(3stap),
avahi,
ulimit(1),
NSS
BUGS
Use the Bugzilla link of the project web page or our mailing list. http://sourceware.org/systemtap/,
<systemtap@sourceware.org>.
STAP-SERVER(8)