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

opensnoop(8) System Manager's Manual opensnoop(8)

NAME

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

SYNOPSIS

opensnoop [-h] [-T] [-x] [-p PID] [-t TID] [-n name]

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 4.5 feature (bpf_perf_event_output()); for kernels older than 4.5, 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.
-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).
-n name
Only print processes where its name partially matches 'name'

EXAMPLES

Trace all open() syscalls:
# opensnoop
Trace all open() syscalls, and include timestamps:
# opensnoop -T
Trace only open() syscalls that failed:
# opensnoop -x
Trace PID 181 only:
# opensnoop -p 181
Trace all open() syscalls from processes where its name partially matches 'ed':
# opensnoop -n ed

FIELDS

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

SEE ALSO

funccount(1)
2015-08-18 USER COMMANDS