STAP-SERVER(8) System Manager's Manual STAP-SERVER(8)
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:
o management of systemtap compile servers as a service.
o 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 the 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.
-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 one server for each kernel release installed in /lib/modules/. Previous -I, -R, -B and -u
options will be applied to each server, however previous -a options will be ignored and the default architecture will be used.
-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 configura-
tion 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 procss 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.
CONFIGURATION
Configuration files allow us to:
o specify global configuration of logging, server configuration files, status files and other global parameters.
o 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).
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 contains 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. The default location of these files can be overridden in the global configu-
ration 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 architec-
ture of the host will be used.
RELEASE
Specifies the kernel release for this server and corresponds to the -r option (see OPTIONS). If RELEASE 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 ele-
ment 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 an array variable with each element corresponding to
an -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 OPTIONS).
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 option (see OPTIONS).
PORT Specifies the network port to be used by this server and corresponds to the --port option (see OPTIONS).
SSL Specifies the location of the NSS certificate database to be used by this server and corresponds to the --ssl option (see OPTIONS).
SERVER AUTHENTICAION
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 certificates. 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 systemtap-server package is installed, the
server's certificate for the default user (stap-server) is automatically 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 system-
tap 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 --privilege 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 set-
up or options required.
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.unprivileged 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 for each kernel 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 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
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. Con-
sider 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 invocation, 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 CONFIGURA-
TION.
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 sta-
tus 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 with resource limits that impose maximum cpu time, file size, memory consumption, in order to bound the effects of
processing excessively large or bogus inputs.
When the user running the servers is stap-server, each server is run with limits equivalent to
ulimit -f 50000 -s 1000 -t 60 -u 20 -v 500000
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 management of certificates. The related certificate databases must be pro-
tected in order to maintain the security 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 certificate 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), stapfuncs(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)