NAME¶

statsnoop - Trace stat() syscalls. Uses Linux eBPF/bcc.

SYNOPSIS¶

statsnoop [-h] [-t] [-x] [-p PID]

DESCRIPTION¶

statsnoop traces the different stat() syscalls, showing which processes are attempting to read information about which files. This can be useful for determining the location of config and log files, or for troubleshooting applications that are failing, especially on startup.

This works by tracing various kernel sys_stat() functions using dynamic tracing, and will need updating to match any changes to these functions.

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: in seconds since the first event, with decimal places.

-x

Only print failed stats.

-p PID

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

EXAMPLES¶

Trace all stat() syscalls:

# statsnoop

Trace all stat() syscalls, and include timestamps:

# statsnoop -t

Trace only stat() syscalls that failed:

# statsnoop -x

Trace PID 181 only:

# statsnoop -p 181

FIELDS¶

TIME(s)

Time of the call, in seconds.

PID

Process 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 stat 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 stat()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

AUTHOR¶

Brendan Gregg

SEE ALSO¶

opensnoop(1)