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Demonstrations of execsnoop, the Linux eBPF/bcc version.
execsnoop traces new processes. For example, tracing the commands invoked when
running "man ls":
# ./execsnoop
PCOMM PID RET ARGS
bash 15887 0 /usr/bin/man ls
preconv 15894 0 /usr/bin/preconv -e UTF-8
man 15896 0 /usr/bin/tbl
man 15897 0 /usr/bin/nroff -mandoc -rLL=169n -rLT=169n -Tutf8
man 15898 0 /usr/bin/pager -s
nroff 15900 0 /usr/bin/locale charmap
nroff 15901 0 /usr/bin/groff -mtty-char -Tutf8 -mandoc -rLL=169n -rLT=169n
groff 15902 0 /usr/bin/troff -mtty-char -mandoc -rLL=169n -rLT=169n -Tutf8
groff 15903 0 /usr/bin/grotty
The output shows the parent process/command name (PCOMM), the PID, the return
value of the exec() (RET), and the filename with arguments (ARGS).
This works by traces the execve() system call (commonly used exec() variant),
and shows details of the arguments and return value. This catches new processes
that follow the fork->exec sequence, as well as processes that re-exec()
themselves. Some applications fork() but do not exec(), eg, for worker
processes, which won't be included in the execsnoop output.
The -x option can be used to include failed exec()s. For example:
# ./execsnoop -x
PCOMM PID RET ARGS
supervise 9660 0 ./run
supervise 9661 0 ./run
mkdir 9662 0 /bin/mkdir -p ./main
run 9663 0 ./run
chown 9664 0 /bin/chown nobody:nobody ./main
run 9665 0 /bin/mkdir -p ./main
supervise 9667 0 ./run
run 9660 -2 /usr/local/bin/setuidgid nobody /command/multilog t ./main
chown 9668 0 /bin/chown nobody:nobody ./main
run 9666 0 /bin/chmod 0777 main
run 9663 -2 /usr/local/bin/setuidgid nobody /command/multilog t ./main
run 9669 0 /bin/mkdir -p ./main
run 9661 -2 /usr/local/bin/setuidgid nobody /command/multilog t ./main
supervise 9670 0 ./run
[...]
This example shows various regular system daemon activity, including some
failures (trying to execute a /usr/local/bin/setuidgid, which I just noticed
doesn't exist).
A -T option can be used to include a time column, a -t option to include a
timestamp column, and a -n option to match on a name. Regular expressions
are allowed.
For example, matching commands containing "mount":
# ./execsnoop -Ttn mount
TIME TIME(s) PCOMM PID PPID RET ARGS
14:08:23 2.849 mount 18049 1045 0 /bin/mount -p
The -l option can be used to only show command where one of the arguments
matches specified line. The limitation is that we are looking only into first 20
arguments of the command. For example, matching all command where one of the argument
is "testpkg":
# ./execsnoop.py -l testpkg
PCOMM PID PPID RET ARGS
service 3344535 4146419 0 /usr/sbin/service testpkg status
systemctl 3344535 4146419 0 /bin/systemctl status testpkg.service
yum 3344856 4146419 0 /usr/local/bin/yum remove testpkg
python 3344856 4146419 0 /usr/local/bin/python /usr/local/bin/yum remove testpkg
yum 3344856 4146419 0 /usr/bin/yum remove testpkg
yum 3345086 4146419 0 /usr/local/bin/yum install testpkg
python 3345086 4146419 0 /usr/local/bin/python /usr/local/bin/yum install testpkg
yum 3345086 4146419 0 /usr/bin/yum install testpkg
rpm 3345452 4146419 0 /bin/rpm -qa testpkg
The --cgroupmap option filters based on a cgroup set. It is meant to be used
with an externally created map.
# ./execsnoop --cgroupmap /sys/fs/bpf/test01
For more details, see docs/special_filtering.md
The -U option include UID on output:
# ./execsnoop -U
UID PCOMM PID PPID RET ARGS
1000 ls 171318 133702 0 /bin/ls --color=auto
1000 w 171322 133702 0 /usr/bin/w
The -u options filters output based process UID. You also can use username as
argument, in that cause UID will be looked up using getpwnam (see man 3 getpwnam).
# ./execsnoop -Uu 1000
UID PCOMM PID PPID RET ARGS
1000 ls 171335 133702 0 /bin/ls --color=auto
1000 man 171340 133702 0 /usr/bin/man getpwnam
1000 bzip2 171341 171340 0 /bin/bzip2 -dc
1000 bzip2 171342 171340 0 /bin/bzip2 -dc
1000 bzip2 171345 171340 0 /bin/bzip2 -dc
1000 manpager 171355 171340 0 /usr/bin/manpager
1000 less 171355 171340 0 /usr/bin/less
USAGE message:
# ./execsnoop -h
usage: execsnoop.py [-h] [-T] [-t] [-x] [--cgroupmap CGROUPMAP] [-u USER] [-q]
[-n NAME] [-l LINE] [-U] [--max-args MAX_ARGS]
Trace exec() syscalls
optional arguments:
-h, --help show this help message and exit
-T, --time include time column on output (HH:MM:SS)
-t, --timestamp include timestamp on output
-x, --fails include failed exec()s
--cgroupmap CGROUPMAP
trace cgroups in this BPF map only
--mntnsmap MNTNSMAP trace mount namespaces in this BPF map only
-u USER, --uid USER trace this UID only
-q, --quote Add quotemarks (") around arguments.
-n NAME, --name NAME only print commands matching this name (regex), any
arg
-l LINE, --line LINE only print commands where arg contains this line
(regex)
-U, --print-uid print UID column
--max-args MAX_ARGS maximum number of arguments parsed and displayed,
defaults to 20
examples:
./execsnoop # trace all exec() syscalls
./execsnoop -x # include failed exec()s
./execsnoop -T # include time (HH:MM:SS)
./execsnoop -U # include UID
./execsnoop -u 1000 # only trace UID 1000
./execsnoop -u root # get root UID and trace only this
./execsnoop -t # include timestamps
./execsnoop -q # add "quotemarks" around arguments
./execsnoop -n main # only print command lines containing "main"
./execsnoop -l tpkg # only print command where arguments contains "tpkg"
./execsnoop --cgroupmap mappath # only trace cgroups in this BPF map
./execsnoop --mntnsmap mappath # only trace mount namespaces in the map