opensnoop_example.txt

Demonstrations of opensnoop, the Linux bpftrace/eBPF version.


opensnoop traces the open() syscall system-wide, and prints various details.
Example output:

# opensnoop.bt
Attaching 3 probes...
Tracing open syscalls... Hit Ctrl-C to end.
PID    COMM               FD ERR PATH
2440   snmp-pass           4   0 /proc/cpuinfo
2440   snmp-pass           4   0 /proc/stat
25706  ls                  3   0 /etc/ld.so.cache
25706  ls                  3   0 /lib/x86_64-linux-gnu/libselinux.so.1
25706  ls                  3   0 /lib/x86_64-linux-gnu/libc.so.6
25706  ls                  3   0 /lib/x86_64-linux-gnu/libpcre.so.3
25706  ls                  3   0 /lib/x86_64-linux-gnu/libdl.so.2
25706  ls                  3   0 /lib/x86_64-linux-gnu/libpthread.so.0
25706  ls                  3   0 /proc/filesystems
25706  ls                  3   0 /usr/lib/locale/locale-archive
25706  ls                  3   0 .
1744   snmpd               8   0 /proc/net/dev
1744   snmpd              21   0 /proc/net/if_inet6
1744   snmpd              21   0 /sys/class/net/eth0/device/vendor
1744   snmpd              21   0 /sys/class/net/eth0/device/device
1744   snmpd              21   0 /proc/sys/net/ipv4/neigh/eth0/retrans_time_ms
1744   snmpd              21   0 /proc/sys/net/ipv6/neigh/eth0/retrans_time_ms
1744   snmpd              21   0 /proc/sys/net/ipv6/conf/eth0/forwarding
1744   snmpd              21   0 /proc/sys/net/ipv6/neigh/eth0/base_reachable_time_ms
1744   snmpd              -1   2 /sys/class/net/lo/device/vendor
1744   snmpd              21   0 /proc/sys/net/ipv4/neigh/lo/retrans_time_ms
1744   snmpd              21   0 /proc/sys/net/ipv6/neigh/lo/retrans_time_ms
1744   snmpd              21   0 /proc/sys/net/ipv6/conf/lo/forwarding
1744   snmpd              21   0 /proc/sys/net/ipv6/neigh/lo/base_reachable_time_ms
2440   snmp-pass           4   0 /proc/cpuinfo
2440   snmp-pass           4   0 /proc/stat
22884  pickup             12   0 maildrop
2440   snmp-pass           4   0 /proc/cpuinfo
2440   snmp-pass           4   0 /proc/stat

While tracing, at "ls" command was launched: the libraries it uses can be seen
as they were opened. Also, the snmpd process opened various /proc and /sys
files (reading metrics).
was starting up: a new process).

opensnoop can be useful for discovering configuration and log files, if used
during application startup.


There is another version of this tool in bcc: https://github.com/iovisor/bcc
The bcc version provides command line options to customize the output.