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)