1opensnoop(8) System Manager's Manual opensnoop(8)
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6 opensnoop - Trace open() syscalls. Uses Linux eBPF/bcc.
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9 opensnoop [-h] [-T] [-U] [-x] [-p PID] [-t TID] [-u UID]
10 [-d DURATION] [-n NAME] [-e] [-f FLAG_FILTER] [-F]
11 [--cgroupmap MAPPATH] [--mntnsmap MAPPATH]
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14 opensnoop traces the open() syscall, showing which processes are at‐
15 tempting to open which files. This can be useful for determining the
16 location of config and log files, or for troubleshooting applications
17 that are failing, specially on startup.
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19 This works by tracing the kernel sys_open() function using dynamic
20 tracing, and will need updating to match any changes to this function.
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22 This makes use of a Linux 4.4 feature (bpf_perf_event_output()); for
23 kernels older than 4.4, see the version under tools/old, which uses an
24 older mechanism.
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26 Since this uses BPF, only the root user can use this tool.
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29 CONFIG_BPF and bcc.
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32 -h Print usage message.
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34 -T Include a timestamp column.
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36 -U Show UID.
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38 -x Only print failed opens.
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40 -p PID Trace this process ID only (filtered in-kernel).
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42 -t TID Trace this thread ID only (filtered in-kernel).
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44 -u UID Trace this UID only (filtered in-kernel).
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46 -d DURATION
47 Total duration of trace in seconds.
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49 -n name
50 Only print processes where its name partially matches 'name'
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52 -e Show extended fields.
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54 -f FLAG
55 Filter on open() flags, e.g., O_WRONLY.
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57 -F Show full path for an open file with relative path.
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59 --cgroupmap MAPPATH
60 Trace cgroups in this BPF map only (filtered in-kernel).
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62 --mntnsmap MAPPATH
63 Trace mount namespaces in this BPF map only (filtered in-ker‐
64 nel).
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67 Trace all open() syscalls:
68 # opensnoop
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70 Trace all open() syscalls, for 10 seconds only:
71 # opensnoop -d 10
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73 Trace all open() syscalls, and include timestamps:
74 # opensnoop -T
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76 Show UID:
77 # opensnoop -U
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79 Trace only open() syscalls that failed:
80 # opensnoop -x
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82 Trace PID 181 only:
83 # opensnoop -p 181
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85 Trace UID 1000 only:
86 # opensnoop -u 1000
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88 Trace all open() syscalls from processes where its name partially
89 matches 'ed':
90 # opensnoop -n ed
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92 Show extended fields:
93 # opensnoop -e
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95 Only print calls for writing:
96 # opensnoop -f O_WRONLY -f O_RDWR
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98 Trace a set of cgroups only (see special_filtering.md from bcc sources
99 for more details):
100 # opensnoop --cgroupmap /sys/fs/bpf/test01
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103 TIME(s)
104 Time of the call, in seconds.
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106 UID User ID
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108 PID Process ID
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110 TID Thread ID
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112 COMM Process name
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114 FD File descriptor (if success), or -1 (if failed)
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116 ERR Error number (see the system's errno.h)
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118 FLAGS Flags passed to open(2), in octal
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120 PATH Open path
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123 This traces the kernel open function and prints output for each event.
124 As the rate of this is generally expected to be low (< 1000/s), the
125 overhead is also expected to be negligible. If you have an application
126 that is calling a high rate of open()s, then test and understand over‐
127 head before use.
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130 This is from bcc.
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132 https://github.com/iovisor/bcc
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134 Also look in the bcc distribution for a companion _examples.txt file
135 containing example usage, output, and commentary for this tool.
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138 Linux
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141 Unstable - in development.
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144 Brendan Gregg, Rocky Xing
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147 execsnoop(8), funccount(1)
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151USER COMMANDS 2020-02-20 opensnoop(8)