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NAME | C SYNOPSIS | DESCRIPTION | CONTAINERS | PROCESSES | DIAGNOSTICS | SEE ALSO | COLOPHON |
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PMDAROOTCONNECT(3) Library Functions Manual PMDAROOTCONNECT(3)
pmdaRootConnect, pmdaRootShutdown, pmdaRootContainerHostName,
pmdaRootContainerProcessID, pmdaRootContainerCGroupName,
pmdaRootProcessStart, pmdaRootProcessWait,
pmdaRootProcessTerminate - privileged PCP collector services
#include <pcp/pmapi.h>
#include <pcp/pmda.h>
int pmdaRootConnect(void);
void pmdaRootShutdown(int fd);
int pmdaRootContainerHostName(int fd, char *name, int namelen,
char *buffer, int buflen);
int pmdaRootContainerProcessID(int fd, char *name, int namelen);
int pmdaRootContainerCGroupName(int fd, char *name, int namelen,
char *buffer, int buflen);
int pmdaRootProcessStart(int fd, int ipctype, char *label,
int labellen, const char *args,
int argslen, int *pid, int *infd,
int *outfd);
int pmdaRootProcessWait(int fd, int pid, int *status);
int pmdaRootProcessTerminate(int fd, int pid);
cc ... -lpcp_pmda -lpcp
pmdaRootConnect initializes an IPC channel between a PCP collector
process - either a PMDA(3) or pmcd(1) itself - and the pmdaroot(1)
server.
On success, the return value from pmdaRootConnect is a unix(7) do‐
main socket file descriptor, which can be subsequently passed to
each of the other APIs described here. This channel can be used
to perform limited privilege escalation for specific scenarios
needed by PCP collector services. The channel can be deactivated
using the pmdaRootShutdown interface.
Several interfaces are provided for access to the container facil‐
ities of modern Linux distributions, as needed by various agents
accessing kernel features related to containers.
pmdaRootContainerHostName allows lookup of the current hostname
for a named container on behalf of an unprivileged process, via
the setns(3) system call on Linux. On success, the hostname is
returned in the supplied buffer, of size buflen and the return
value indicates the length of the hostname.
pmdaRootContainerProcessID performs a name to process identifier
translation - on success, the return value is the identifier of
the first process started (process 1) in the named container.
pmdaRootContainerCGroupName fills the supplied buffer with the en‐
gine-specific names of kernel control groups that have been used
to build the container identified by name. When successful, the
return value indicates the length of the cgroup name resolved for
the container.
The name of the container is interpreted by pmdaroot(1), which at‐
tempts to match up the specified name with one of the implementa‐
tions of containers that it is aware of. Hence, the name argument
is potentially interpreted differently, depending on the installed
container engine, as determined internally by pmdaroot).
In the case of the Docker container engine, for example, a valid
container name can be the unique hash identifier, the human-read‐
able name, or any unique identifier substring. This is the algo‐
rithm used by the Docker client tools themselves.
A second set of interfaces are provided allowing the collector
system to start privileged child processes. In particular, these
are used by pmcd(1) so that it can start privileged PMDAs even
when it is running under an unprivileged account itself.
These interfaces allow processes to be started (pmdaRoot‐
ProcessStart), reaped upon completion (pmdaRootProcessWait), and
forcibly terminated through use of signals (pmdaRootProcessTermi‐
nate). At this stage, they are intended only for use by pmcd it‐
self and as such are described here only for completeness.
All pmdaRoot interfaces will return negative status codes suitable
for passing to pmErrStr_r(3).
pmcd(1), pmdaroot(1), pmErrStr_r(3), PMDA(3), setns(3) and
unix(7).
This page is part of the PCP (Performance Co-Pilot) project. In‐
formation about the project can be found at ⟨http://www.pcp.io/⟩.
If you have a bug report for this manual page, send it to
pcp@groups.io. This page was obtained from the project's upstream
Git repository ⟨https://github.com/performancecopilot/pcp.git⟩ on
2025-08-11. (At that time, the date of the most recent commit
that was found in the repository was 2025-08-11.) If you discover
any rendering problems in this HTML version of the page, or you
believe there is a better or more up-to-date source for the page,
or you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a
mail to man-pages@man7.org
Performance Co-Pilot PCP PMDAROOTCONNECT(3)
Pages that refer to this page: pmdaroot(1)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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