| Demonstrations of opensnoop, the Linux eBPF/bcc version. |
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| opensnoop traces the open() syscall system-wide, and prints various details. |
| Example output: |
| |
| # ./opensnoop |
| PID COMM FD ERR PATH |
| 17326 <...> 7 0 /sys/kernel/debug/tracing/trace_pipe |
| 1576 snmpd 9 0 /proc/net/dev |
| 1576 snmpd 11 0 /proc/net/if_inet6 |
| 1576 snmpd 11 0 /proc/sys/net/ipv4/neigh/eth0/retrans_time_ms |
| 1576 snmpd 11 0 /proc/sys/net/ipv6/neigh/eth0/retrans_time_ms |
| 1576 snmpd 11 0 /proc/sys/net/ipv6/conf/eth0/forwarding |
| 1576 snmpd 11 0 /proc/sys/net/ipv6/neigh/eth0/base_reachable_time_ms |
| 1576 snmpd 11 0 /proc/sys/net/ipv4/neigh/lo/retrans_time_ms |
| 1576 snmpd 11 0 /proc/sys/net/ipv6/neigh/lo/retrans_time_ms |
| 1576 snmpd 11 0 /proc/sys/net/ipv6/conf/lo/forwarding |
| 1576 snmpd 11 0 /proc/sys/net/ipv6/neigh/lo/base_reachable_time_ms |
| 1576 snmpd 9 0 /proc/diskstats |
| 1576 snmpd 9 0 /proc/stat |
| 1576 snmpd 9 0 /proc/vmstat |
| 1956 supervise 9 0 supervise/status.new |
| 1956 supervise 9 0 supervise/status.new |
| 17358 run 3 0 /etc/ld.so.cache |
| 17358 run 3 0 /lib/x86_64-linux-gnu/libtinfo.so.5 |
| 17358 run 3 0 /lib/x86_64-linux-gnu/libdl.so.2 |
| 17358 run 3 0 /lib/x86_64-linux-gnu/libc.so.6 |
| 17358 run -1 6 /dev/tty |
| 17358 run 3 0 /proc/meminfo |
| 17358 run 3 0 /etc/nsswitch.conf |
| 17358 run 3 0 /etc/ld.so.cache |
| 17358 run 3 0 /lib/x86_64-linux-gnu/libnss_compat.so.2 |
| 17358 run 3 0 /lib/x86_64-linux-gnu/libnsl.so.1 |
| 17358 run 3 0 /etc/ld.so.cache |
| 17358 run 3 0 /lib/x86_64-linux-gnu/libnss_nis.so.2 |
| 17358 run 3 0 /lib/x86_64-linux-gnu/libnss_files.so.2 |
| 17358 run 3 0 /etc/passwd |
| 17358 run 3 0 ./run |
| ^C |
| |
| While tracing, the snmpd process opened various /proc files (reading metrics), |
| and a "run" process read various libraries and config files (looks like it |
| was starting up: a new process). |
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| opensnoop can be useful for discovering configuration and log files, if used |
| during application startup. |
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| The -p option can be used to filter on a PID, which is filtered in-kernel. Here |
| I've used it with -t to print timestamps: |
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| ./opensnoop -tp 1956 |
| TIME(s) PID COMM FD ERR PATH |
| 0.000000000 1956 supervise 9 0 supervise/status.new |
| 0.000289999 1956 supervise 9 0 supervise/status.new |
| 1.023068000 1956 supervise 9 0 supervise/status.new |
| 1.023381997 1956 supervise 9 0 supervise/status.new |
| 2.046030000 1956 supervise 9 0 supervise/status.new |
| 2.046363000 1956 supervise 9 0 supervise/status.new |
| 3.068203997 1956 supervise 9 0 supervise/status.new |
| 3.068544999 1956 supervise 9 0 supervise/status.new |
| |
| This shows the supervise process is opening the status.new file twice every |
| second. |
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| The -x option only prints failed opens: |
| |
| # ./opensnoop -x |
| PID COMM FD ERR PATH |
| 18372 run -1 6 /dev/tty |
| 18373 run -1 6 /dev/tty |
| 18373 multilog -1 13 lock |
| 18372 multilog -1 13 lock |
| 18384 df -1 2 /usr/share/locale/en_US.UTF-8/LC_MESSAGES/coreutils.mo |
| 18384 df -1 2 /usr/share/locale/en_US.utf8/LC_MESSAGES/coreutils.mo |
| 18384 df -1 2 /usr/share/locale/en_US/LC_MESSAGES/coreutils.mo |
| 18384 df -1 2 /usr/share/locale/en.UTF-8/LC_MESSAGES/coreutils.mo |
| 18384 df -1 2 /usr/share/locale/en.utf8/LC_MESSAGES/coreutils.mo |
| 18384 df -1 2 /usr/share/locale/en/LC_MESSAGES/coreutils.mo |
| 18385 run -1 6 /dev/tty |
| 18386 run -1 6 /dev/tty |
| |
| This caught a df command failing to open a coreutils.mo file, and trying from |
| different directories. |
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| The ERR column is the system error number. Error number 2 is ENOENT: no such |
| file or directory. |
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| USAGE message: |
| |
| # ./opensnoop -h |
| usage: opensnoop [-h] [-t] [-x] [-p PID] |
| |
| Trace open() syscalls |
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| optional arguments: |
| -h, --help show this help message and exit |
| -t, --timestamp include timestamp on output |
| -x, --failed only show failed opens |
| -p PID, --pid PID trace this PID only |
| |
| examples: |
| ./opensnoop # trace all open() syscalls |
| ./opensnoop -t # include timestamps |
| ./opensnoop -x # only show failed opens |
| ./opensnoop -p 181 # only trace PID 181 |