Sysdig

Garbage In, Garbage Out
syscalls syscalls
*may contain traces of signals and shared memory

Syscalls
ssize_t read(int fd, void *buf, size_t count);
ssize_t write(int fd, const void *buf, size_t count);
int open(const char *pathname, int flags, mode_t mode);
int close(int fd);
int stat(const char *path, struct stat *buf);
...
!
$ grep -c __NR_ /usr/include/asm/unistd_64.h
313
!
$ man 2 read

strace
# strace cat /etc/hostname
execve("/bin/cat", ["cat", "/etc/hostname"], ...
brk(0) = 0x1675000
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT
mmap(NULL, 8192, PROT_READ|PROT_WRITE, ...
access("/etc/ld.so.preload", R_OK) = -1 ENOENT
open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=48577, ...}) = 0
mmap(NULL, 48577, PROT_READ, MAP_PRIVATE, 3, 0) = ...
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT
(...)

that’s cool, but…
1 m illion sysca lls, as fast as possible
worst case for a ny tracer
# dd if=/dev/zero of=/dev/null bs=1k count=1M
1048576+0 records in
1048576+0 records out
1073741824 bytes (1.1 GB) copied, 0.332905 s, 3.2 GB/s
# strace -o /dev/null !!
1073741824 bytes (1.1 GB) copied, 18.2365 s, 58.9 MB/s
50x overhead

@brendangregg’s
http://www.slideshare.net/brendangregg/linux-performance-tools-2014

hello, sysdig
# sysdig | head -5
3 15:26:36.552482922 0 sysdig (7311) > switch
next=329(systemd-udevd) pgft_maj=6 pgft_min=1432
vm_size=26740 vm_rss=3052 vm_swap=0
4 15:26:36.552502349 0 systemd-udevd (329) < read
res=2352 data=# This file is part of systemd..#.#
systemd is free software; you can redistri
5 15:26:36.552590722 0 systemd-udevd (329) > read
fd=12(<f>/lib/udev/rules.d/42-usb-hid-pm.rules)
size=4096
res=0 data=
7 15:26:36.552596220 0 systemd-udevd (329) > close

hello, sysdig
# sysdig | head -5
3 15:26:36.552482922 0 sysdig (7311) > switch
size=4096
res=0 data=
event number, timestamp

hello, sysdig
# sysdig | head -5
3 15:26:36.552482922 0 sysdig (7311) > switch
size=4096
res=0 data=
CPU number, process name, pid

hello, sysdig
# sysdig | head -5
3 15:26:36.552482922 0 sysdig (7311) > switch
size=4096
res=0 data=
event direction, event type

hello, sysdig
enter event
# sysdig | head -5
3 15:26:36.552482922 0 sysdig (7311) > switch
size=4096
res=0 data=
exit event
syscall

hello, sysdig
# sysdig | head -5
3 15:26:36.552482922 0 sysdig (7311) > switch
size=4096
res=0 data=
arbitrary event attributes

events
# sysdig -L
(...)
> open()
< open(FD fd, FSPATH name, FLAGS32 flags, UINT32
mode)
> close(FD fd)
< close(ERRNO res)
> read(FD fd, UINT32 size)
< read(ERRNO res, BYTEBUF data)
> write(FD fd, UINT32 size)
< write(ERRNO res, BYTEBUF data)
(...)

dd
kernel

dd
kernel
strace
1073741824 bytes (1.1 GB) copied, 18.2365 s, 58.9 MB/s

dd
kernel
sysdig
ring buffer
1073741824 bytes (1.1 GB) copied, 1.30029 s, 826 MB/s

filters
fd.name FD full name. If the fd is a file, this
field contains the full path. If the FD
is a socket, this field contain the
connection tuple.
!
proc.apid the pid of one of the process
ancestors.
!
evt.latency delta between an exit event and the
correspondent enter event.
!
(...)
!
# sysdig -l | grep -Ec '^[a-z0-9_.]+'
88

filters
# sysdig fd.name contains shadow
2303 17:30:34.645573185 0 cat (24012) < open
fd=-13(EACCES) name=/etc/shadow flags=1(O_RDONLY)
mode=0
!
# sysdig evt.res = EACCES or evt.res = EPERM
617 17:32:16.197820784 0 cat (24027) < open
fd=-13(EACCES) name=/etc/shadow flags=1(O_RDONLY)
mode=0
4333 17:32:26.239052264 0 killall (24028) < kill
res=-1(EPERM)

back to that dd again…
# sysdig proc.name=not_dd > /dev/null & dd if=/dev/
zero of=/dev/null bs=1k count=1M ; killall sysdig
[1] 24070

output formatting
sa m e as filters (mostly)
# sysdig -p '%user.name %proc.name %fd.name: %evt.res'
evt.failed = true
ubuntu cat /etc/shadow: EACCES
ubuntu cat /usr/share/locale/en_US.UTF-8/LC_MESSAGES/
libc.mo: ENOENT
ubuntu cat /usr/share/locale/en_US.utf8/LC_MESSAGES/
libc.mo: ENOENT
ubuntu cat /usr/share/locale/en_US/LC_MESSAGES/
libc.mo: ENOENT

bottleneck in a haystack
# sysdig -p '%evt.latency.s.%evt.latency.ns %evt.dir
%evt.type %fd.name' fd.type contains ip and fd.sport != 22
(...)
0.000000000 >sendto 192.168.1.118:36220->46.28.247.84:80
0.000114365 <sendto 192.168.1.118:36220->46.28.247.84:80
0.000000000 >recvfrom 192.168.1.118:36220->46.28.247.84:80
0.000005090 <recvfrom 192.168.1.118:36220->46.28.247.84:80
0.000000000 >close 192.168.1.118:36220->46.28.247.84:80
0.000001587 <close 192.168.1.118:36220->46.28.247.84:80

sysdig -w
sysdig -r
sysdig -r
sysdig -r
.scap file
shit’s on fire, yo
capture trace file,
restore service analyze trace at your leisure

lies, damn lies and benchmarks
sysdig -w
sysdig -r
sysdig -r
sysdig -r
.scap file
do a single
benchmark run
analyze/postprocess
lots of ways

chisels: higher level of awesome
Lua
sysdig -cl
sysdig -i chisel_name
sysdig -c chisel_name [args…]

chisel all the things!
# sysdig -cl | grep -c ^[a-z]
37
# find /usr/share/sysdig/chisels/ -name '*.lua' | wc -l
42
the extra ones a re utilities to use in ch isels
(json, A NSI term ina l, etc.)

chisels: performance
bottlenecks Slowest system calls
fileslower Trace slow file I/O
netlower Trace slow network I/O
proc_exec_time Show process execution time
scallslower Trace slow syscalls
topscalls Top system calls by number of calls
topscalls_time Top system calls by time
yu p, a ty po ;)

chisels: security
list_login_shells List the login shell IDs
!
shellshock_detect print shellshock attacks
!
spy_users Display interactive user activity
power corru pts,
absolute power is even more fun

All right gentlemen,
we need some system info
lsof, ps, n etstat
lsof, ps, netstat
with time travel
http://draios.com/ps-lsof-netstat-time-travel/

version 0.1.91
do you feel lucky?
• some syscalls not yet implemented (no args)
• it did crash once (fixed immediately though)
• PID namespaces ignored
• root/privileged user only
• one sysdig process at a time
way better tha n strace though

Sysdig

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