opensnoop(8) System Manager's Manual opensnoop(8)
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 at-
tempting 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-ker-
nel).
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 over-
head 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)
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