10.16 Invoking guix processes

The guix processes command can be useful to developers and system administrators, especially on multi-user machines and on build farms: it lists the current sessions (connections to the daemon), as well as information about the processes involved²⁶. Here’s an example of the information it returns:

$ sudo guix processes
SessionPID: 19002
ClientPID: 19090
ClientCommand: guix shell python

SessionPID: 19402
ClientPID: 19367
ClientCommand: guix publish -u guix-publish -p 3000 -C 9 …

SessionPID: 19444
ClientPID: 19419
ClientCommand: cuirass --cache-directory /var/cache/cuirass …
LockHeld: /gnu/store/…-perl-ipc-cmd-0.96.lock
LockHeld: /gnu/store/…-python-six-bootstrap-1.11.0.lock
LockHeld: /gnu/store/…-libjpeg-turbo-2.0.0.lock
ChildPID: 20495
ChildCommand: guix offload x86_64-linux 7200 1 28800
ChildPID: 27733
ChildCommand: guix offload x86_64-linux 7200 1 28800
ChildPID: 27793
ChildCommand: guix offload x86_64-linux 7200 1 28800

In this example we see that guix-daemon has three clients: guix environment, guix publish, and the Cuirass continuous integration tool; their process identifier (PID) is given by the ClientPID field. The SessionPID field gives the PID of the guix-daemon sub-process of this particular session.

The LockHeld fields show which store items are currently locked by this session, which corresponds to store items being built or substituted (the LockHeld field is not displayed when guix processes is not running as root). Last, by looking at the ChildPID and ChildCommand fields, we understand that these three builds are being offloaded (see Using the Offload Facility).

The output is in Recutils format so we can use the handy recsel command to select sessions of interest (see Selection Expressions in GNU recutils manual). As an example, the command shows the command line and PID of the client that triggered the build of a Perl package:

$ sudo guix processes | \
    recsel -p ClientPID,ClientCommand -e 'LockHeld ~ "perl"'
ClientPID: 19419
ClientCommand: cuirass --cache-directory /var/cache/cuirass …

Additional options are listed below.

--format=format

-f format

Produce output in the specified format, one of:

recutils

The default option. It outputs a set of Session recutils records that include each ChildProcess as a field.

normalized

Normalize the output records into record sets (see Record Sets in GNU recutils manual). Normalizing into record sets allows joins across record types. The example below lists the PID of each ChildProcess and the associated PID for Session that spawned the ChildProcess where the Session was started using guix build.

$ guix processes --format=normalized | \
    recsel \
    -j Session \
    -t ChildProcess \
    -p Session.PID,PID \
    -e 'Session.ClientCommand ~ "guix build"'
PID: 4435
Session_PID: 4278

PID: 4554
Session_PID: 4278

PID: 4646
Session_PID: 4278