NAME

       opensnoop - Trace open() syscalls. Uses Linux eBPF/bcc.

SYNOPSIS

       opensnoop [-h] [-T] [-U] [-x] [-p PID] [-t TID] [-u UID]
                    [-d DURATION] [-n NAME] [-e] [-f FLAG_FILTER] [-F]
                    [--cgroupmap MAPPATH] [--mntnsmap MAPPATH]

DESCRIPTION

       opensnoop traces the open() syscall, showing which processes are attempting to open which files. This can
       be  useful for determining the location of config and log files, or for troubleshooting applications that
       are failing, specially on startup.

       This works by tracing the kernel sys_open() function using dynamic tracing, and  will  need  updating  to
       match any changes to this function.

       This  makes  use  of  a  Linux 4.4 feature (bpf_perf_event_output()); for kernels older than 4.4, see the
       version under tools/old, which uses an older mechanism.

       Since this uses BPF, only the root user can use this tool.

REQUIREMENTS

       CONFIG_BPF and bcc.

OPTIONS

       -h     Print usage message.

       -T     Include a timestamp column.

       -U     Show UID.

       -x     Only print failed opens.

       -p PID Trace this process ID only (filtered in-kernel).

       -t TID Trace this thread ID only (filtered in-kernel).

       -u UID Trace this UID only (filtered in-kernel).

       -d DURATION
              Total duration of trace in seconds.

       -n name
              Only print processes where its name partially matches 'name'

       -e     Show extended fields.

       -f FLAG
              Filter on open() flags, e.g., O_WRONLY.

       -F     Show full path for an open file with relative path.

       --cgroupmap MAPPATH
              Trace cgroups in this BPF map only (filtered in-kernel).

       --mntnsmap  MAPPATH
              Trace mount namespaces in this BPF map only (filtered in-kernel).

EXAMPLES

       Trace all open() syscalls:
              # opensnoop

       Trace all open() syscalls, for 10 seconds only:
              # opensnoop -d 10

       Trace all open() syscalls, and include timestamps:
              # opensnoop -T

       Show UID:
              # opensnoop -U

       Trace only open() syscalls that failed:
              # opensnoop -x

       Trace PID 181 only:
              # opensnoop -p 181

       Trace UID 1000 only:
              # opensnoop -u 1000

       Trace all open() syscalls from processes where its name partially matches 'ed':
              # opensnoop -n ed

       Show extended fields:
              # opensnoop -e

       Only print calls for writing:
              # opensnoop -f O_WRONLY -f O_RDWR

       Trace a set of cgroups only (see special_filtering.md from bcc sources for more details):
              # opensnoop --cgroupmap /sys/fs/bpf/test01

FIELDS

       TIME(s)
              Time of the call, in seconds.

       UID    User ID

       PID    Process ID

       TID    Thread ID

       COMM   Process name

       FD     File descriptor (if success), or -1 (if failed)

       ERR    Error number (see the system's errno.h)

       FLAGS  Flags passed to open(2), in octal

       PATH   Open path

OVERHEAD

       This traces the kernel open function and prints output for each event. As the rate of this  is  generally
       expected to be low (< 1000/s), the overhead is also expected to be negligible. If you have an application
       that is calling a high rate of open()s, then test and understand overhead before use.

SOURCE

       This is from bcc.

              https://github.com/iovisor/bcc

       Also  look  in  the bcc distribution for a companion _examples.txt file containing example usage, output,
       and commentary for this tool.

OS

       Linux

STABILITY

       Unstable - in development.

AUTHOR

       Brendan Gregg, Rocky Xing

SEE ALSO

       execsnoop(8), funccount(1)

USER COMMANDS                                      2020-02-20                                       opensnoop(8)