stap-server.8

.\" -*- nroff -*-
.TH STAP\-SERVER 8 
.SH NAME
stap\-server \- systemtap compile server management

.SH SYNOPSIS

.br
[
.B service
]
.B stap\-server
{
.B start
|
.B stop
|
.B restart
|
.B condrestart
|
.B try\-restart
|
.B force\-reload
|
.B status
} [
.I options
]

.SH DESCRIPTION

A systemtap compile server listens for connections from stap clients
on a secure SSL network port and accepts requests to run the
.I stap
front end. Each server advertises its presence and configuration on the local
network using mDNS (\fIavahi\fR) allowing for automatic detection by clients.

.PP
The stap\-server script aims to provide:
.IP \(bu 4
management of systemtap compile servers as a service.
.IP \(bu 4
convenient control over configured servers and individual (ad\-hoc) servers.

.SH ARGUMENTS
One of the actions below must be specified:
.TP
.B 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.

.TP
.B 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.

.TP
.B 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 \fIstart\fR.

.TP
.B 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.

.TP
.B try\-restart
This action is identical to \fIcondrestart\fR.

.TP
.B force\-reload
Stop all running servers, reload config files and restart the service as if
.I start
was specified.

.TP
.B 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.

.SH OPTIONS
The following options are used to provide additional configuration and
to specify servers to be managed:

.TP
\fB\-c\fR \fIconfigfile\fR
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 \fB\-c\fR option is specified more than once, the
last
configuration file specified will be used.

.TP
\fB\-a\fR \fIarchitecture\fR
This option specifies the target architecture of the server and is
analogous to the \fB\-a\fR option of \fIstap\fR. See the
.IR stap (1)
manual page for more details.
The default architecture is the architecture of the host.

.TP
\fB\-r\fR \fIkernel\-release\fR
This option specifies the target kernel release of the server and is
analogous to the \fB\-r\fR option of \fIstap\fR. See the
.IR stap (1)
manual page for more details.
The default release is that of the currently running kernel.

.TP
\fB\-I\fR \fIpath\fR
This option specifies an additional path to be searched by the server(s) for
tapsets and is analogous to the \fB\-I\fR option of \fIstap\fR.
See the
.IR stap (1)
manual page for more details.

.TP
\fB\-R\fR \fIpath\fR
This option specifies the location of the systemtap runtime to be used by the
server(s) and is analogous to the \fB\-R\fR option of \fIstap\fR.
See the
.IR stap (1)
manual page for more details.

.TP
\fB\-B\fR \fIoptions\fR
This option specifies options to be passed to \fImake\fR when building systemtap
modules and is analogous to the \fB\-B\fR option of \fIstap\fR.
See the
.IR stap (1)
manual page for more details.

.TP
\fB\-i\fR
This option is a shortcut which specifies one server for each kernel
release installed in \fI/lib/modules/\fR. Previous
\fB\-I\fR, \fB\-R\fR, \fB\-B\fR and \fB\-u\fR options will be
applied to each server, however previous \fB\-a\fR options will be ignored and
the default architecture will be used.

.TP
\fB\-n\fR \fInickname\fR
This option allows the specification of a server configuration by nickname.
When \fB\-n\fR 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
\fB\-c\fR option. If a server configuration for the given
nickname is found, the
\fB\-a\fR, \fB\-r\fR, \fB\-I\fR, \fB\-R\fR, \fB\-B\fR and \fB\-u\fR 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
.I start
(or an action behaving like \fIstart\fR
(see \fBARGUMENTS\fR), the server will be started with the given nickname.
If no configuration with the given nickname is found, and the action is not
.I start
(or an action behaving like \fIstart\fR), it is an error. If a nickname is
not specified for a server which is being started, its nickname will be its
process id.

.TP
\fB\-p\fR \fIpid\fR
This option allows the specification of a server configuration by process id.
When \fB\-p\fR 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
\fB\-a\fR, \fB\-r\fR, \fB\-I\fR, \fB\-R\fR, \fB\-B\fR and \fB\-u\fR options for
that server will be used as if they were specified on the command line.

.TP
\fB\-u\fR \fIuser\-name\fR
Each systemtap compile server is normally run by the user name
\fIstap\-server\fR (for the initscript) or as the user invoking
\fIstap\-server\fR,
unless otherwise configured (see \fBFILES\fR). This option
specifies the user name used to run the server(s). The user name specified
must be a member of the group \fIstap\-server\fR.

.TP
\fB\-\-log\fR \fIlogfile\fR
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 \fBFILES\fR) will be used for subsequent servers.

.TP
\fB\-\-port\fR \fIport\-number\fR
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.

.TP
\fB\-\-ssl\fR \fIcertificate\-db\-path\fR
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 \fBFILES\fR) for subsequent servers.

.TP
\fB\-\-max\-threads\fR \fIthreads\fR
This option allows the specification of the maximum number of worker threads
to handle concurrent requests. If \fIthreads\fR == 0, each request will be
handled on the main thread, serially.  The default is the number of available
processor cores.

.SH CONFIGURATION

Configuration files allow us to:
.IP \(bu 4
specify global configuration of logging, server configuration files, status
files and other global parameters.
.IP \(bu 4
specify which servers are to be started by default.

.SH 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 \fIVARIABLE=VALUE\fR. 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:

.TP
.B CONFIG_PATH
Specifies the absolute path of the directory containing the default server
configurations.

.TP
.B STAT_PATH
Specifies the absolute path of the running server status directory.

.TP
.B LOG_FILE
Specifies the absolute path of the log file.

.TP
.B STAP_USER
Specifies the userid which will be used to run the server(s)
(default: for the initscript \fIstap\-server\fR, otherwise the user running
\fIstap\-server\fR).

.SH Individual Server Configuration

Each server configuration file configures a server to be started when no
server is specified for the \fIstart\fR action, or an action behaving like the
\fIstart\fR action (see \fIARGUMENTS\fR). 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 \fIVARIABLE=VALUE\fR. 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 \fI.conf\fR. The default
location of these files can be
overridden in the global configuration file using the \fB\-c\fR option
(see \fIOPTIONS\fR).

The following variables may be assigned:
.TP
.B ARCH
Specifies the target architecture for this server and corresponds to the
\fB\-a\fR option (see \fIOPTIONS\fR). If \fBARCH\fR is not set, the
architecture of the host will be used.

.TP
.B RELEASE
Specifies the kernel release for this server
and corresponds to the
\fB\-r\fR option (see \fIOPTIONS\fR). If \fBRELEASE\fR is not set, the
release
of the kernel running on the host will be used.
 
.TP
.B BUILD
Specifies options to be passed to the \fImake\fR process used by
\fIsystemtap\fR to build kernel modules.
This an array variable with each element corresponding to a
\fB\-B\fR option (see \fIOPTIONS\fR). Using the form \fBBUILD=STRING\fR clears
the array and sets the first element to \fBSTRING\fR. Using the form
\fBBUILD+=STRING\fR adds \fBSTRING\fR as an additional element to the array.
 
.TP
.B INCLUDE
Specifies a list of directories to be searched by the server for tapsets.
This an array variable with each element corresponding to an
\fB\-I\fR option (see \fIOPTIONS\fR). Using the form \fBINCLUDE=PATH\fR clears
the array and sets the first element to \fBPATH\fR. Using the form
\fBINCLUDE+=PATH\fR adds \fBPATH\fR as an additional element to the array.

.TP
.B RUNTIME
Specifies the directory which contains the systemtap runtime code to be used
by this server
and corresponds to the
\fB\-R\fR option (see \fIOPTIONS\fR).

.TP
.B USER
Specifies the user name to be used to run this server
and corresponds to the
\fB\-u\fR option (see \fIOPTIONS\fR).

.TP
.B NICKNAME
Specifies the nickname to be used to refer to this server
and corresponds to the
\fB\-n\fR option (see \fIOPTIONS\fR).

.TP
.B LOG
Specifies the location of the log file to be used by this server and corresponds to the
\fB\-\-log\fR option (see \fIOPTIONS\fR).

.TP
.B PORT
Specifies the network port to be used by this server and corresponds to the
\fB\-\-port\fR option (see \fIOPTIONS\fR).

.TP
.B SSL
Specifies the location of the NSS certificate database to be used by this server and corresponds
to the
\fB\-\-ssl\fR option (see \fIOPTIONS\fR).

.TP
.B MAXTHREADS
Specifies the maximum number of worker threads to handle concurrent requests to be used by this server
and corresponds to the \fB\-\-max\-threads\fR option (see \fIOPTIONS\fR).

.SH SERVER AUTHENTICAION
The security of the SSL network connection between the client and server
depends on the proper
management of server certificates.

.PP
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\[aq]s certificate to the
client\[aq]s database of trusted servers.

.PP
For the \fIstap\-server\fR initscript, on the local host, this is handled
automatically.
When the \fIsystemtap\-server\fR package is installed, the server\[aq]s
certificate for the default user (\fIstap\-server\fR) is automatically
generated and installed. This means that servers started by the
\fIstap\-server\fR initscript,
with the default user, are automatically trusted by clients on the local
host, both as an SSL peer and as a systemtap 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 \fI\-\-use\-server\fR
and \fI\-\-privilege\fR
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.

.PP
In order to use a server running on another host, that server\[aq]s certificate
must be installed on the client\[aq]s host.
See the \fI\-\-trust\-servers\fR option in the
.IR stap (1)
manual page for more details and README.unprivileged in the systemtap sources
for more details..

.SH EXAMPLES
See the 
.IR stapex (3stap)
manual page for a collection of sample \fIsystemtap\fR scripts.
.PP
To start the configured servers, or the default server, if none are configured:
.PP
.B \& $ [ service ] stap\-server start
.PP
To start a server for each kernel installed in /lib/modules:
.PP
.B \& $ [ service ] stap\-server start \-i
.PP
To obtain information about the running server(s):
.PP
.B \& $ [ service ] stap\-server status
.PP
To start a server like another one, except targeting a different architecture,
by referencing the first server\[aq]s nickname:
.PP
.B \& $ [ service ] stap\-server start \-n \fINICKNAME\fR \-a \fIARCH\fR
.PP
To stop one of the servers by referencing its process id (obtained by running
\fBstap\-server status\fR):
.PP
.B \& $ [ service ] stap\-server stop \-p \fIPID\fR
.PP
To run a script using a compile server:
.PP
.B \& $ stap SCRIPT \-\-use\-server
.PP
To run a script as an unprivileged user using a compile server:
.PP
.B \& $ stap SCRIPT
.PP
To stop all running servers:
.PP
.B \& $ [ service ] stap\-server stop

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

.PP
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.
.TP
1
Run stap\-server as an unprivileged user, never as root.

When invoked as a
service (i.e. \fBservice stap\-server\fR ...), each server is run,
by default, as the user \fIstap\-server\fR.
When invoked directly (i.e. \fBstap\-server\fR ...), each server is run,
by default, as the invoking user. In each case, another user may be selected by
using the \fI\-u\fR option on invocation, by specifying
\fISTAP_USER=\fRusername in the global configuration file or by specifying
\fIUSER=\fRusername in an individual server configuration file. The invoking
user must have authority to run processes as another user.
See \fICONFIGURATION\fR.

The selected user must have write access to the server log file.
The location of the server log file may
be changed by setting \fILOG_FILE=\fRpath in the global configuration file.
See \fICONFIGURATION\fR.

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 \fISTAT_PATH=\fRpath in the global
configuration file.
See \fICONFIGURATION\fR.

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.

.TP
2
Run stap\-server requests 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 server is \fIstap\-server\fR,
each server request is run with limits specified in \fI~stap-server/.systemtap/rc\fR
otherwise, no limits are imposed.

.TP
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 \fI/tmp/\fR.

.TP
4
Activate network firewalls to limit stap client connections
to relatively trustworthy networks.

For automatic selection of servers by clients, \fIavahi\fR must be installed
on both the server and client hosts and \fImDNS\fR messages must be allowed through the firewall.

.PP
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 protected 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.

.SH FILES
.TP
Important files and their corresponding paths can be located in the 
stappaths (7) manual page.

.SH SEE ALSO
.IR stap (1),
.IR staprun (8),
.IR stapprobes (3stap),
.IR stappaths (7),
.IR stapex (3stap),
.IR avahi ,
.IR ulimit (1),
.IR NSS

.SH BUGS
Use the Bugzilla link of the project web page or our mailing list.
.nh
.BR http://sourceware.org/systemtap/ ", " <systemtap@sourceware.org> .
.hy