Make patch file and apply it.

Environment and Prerequisite

• Linux base system
• Bash shell(/bin/bash)
• patch, diff and git command

patch, diff and git command

patch command

patch -pNUM < patchfile

• patch : Apply a patch file to an project or file.
• Patch file can be made by using diff or git diff.

diff command

diff [OPTION]... FILES

• diff : Compare files or projects line by line
• Detail example is in below.

git diff command

git diff

• git diff : Show current git project’s diff status.
• You can make patch file using git diff command.

Make patch file using diff

Make patch file between two files

Usage

diff -urN [old file] [patched file]

Example

# Make diff
diff -urN test-old.txt test-new.txt

# Make patch file
diff -urN test-old.txt test-new.txt > patch.patch

Make patch file between two project directories

Usage

diff -urN [old directory] [patched directory]

Example

# Make diff
diff -urN neutron neutron_patched

# Make diff file
diff -urN neutron neutron_patched > neutron_patch.patch

Make patch file using git diff

• Directly use git command

git diff > [patch file name]

Apply patch file

Usage

patch -pNUM < patchfile

• In project or file directory that you want to apply patch, use above command.
• NUM means that how many root directories you are going to remove in patch file. For example, in patch file there is file patch like a/neutron/service.py. If we use -p1 option, then patch will be applied file path neutron/service.py. If we use -p2 option, then patch will be applied to file path service.py.

Example

• Apply patch in neutron project directory
• neutron_patch.patch file must exist just out of neutron project

# In neutron project
cd neutron

# Apply patch file
# Option -p1 could be different depends on your patch file
patch -p1 < ../neutron_patch.patch

Usage Example

0. Process

• Clone neutron project and edit it for making patch file. Make patch file from git diff.
• Revert all diffs in neutron project and apply patch file. Check patch is applied.

1. Clone neutron project and modify it

git clone https://github.com/openstack/neutron.git
cd neutron

vi [any file in this project directory]

2. Make patch file

• Make patch file freely.

git diff > ../neutron_patch.patch

neutron_patch.patch

diff --git a/neutron/service.py b/neutron/service.py
index 06bf4cd..67f93fe 100644
--- a/neutron/service.py
+++ b/neutron/service.py
@@ -1,4 +1,4 @@
-# Copyright 2011 VMware, Inc
+#aidfjaldfja;ifdjsaoe# Copyright 2011 VMware, Inc
 # All Rights Reserved.
 #
 #    Licensed under the Apache License, Version 2.0 (the "License"); you may
diff --git a/neutron/worker.py b/neutron/worker.py
index 81e7110..a330fe0 100644
--- a/neutron/worker.py
+++ b/neutron/worker.py
@@ -9,7 +9,7 @@
 #    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 #    License for the specific language governing permissions and limitations
 #    under the License.
-
+#akdfjakl;dfja;kfld
 from neutron_lib import worker
 from oslo_config import cfg
 from oslo_service import loopingcall

2. Apply patch file

• Revert all diffs and run below command to apply patch file

patch -p1 < ../neutron_patch.patch

Reference

• http://man7.org/linux/man-pages/man1/patch.1.html
• http://man7.org/linux/man-pages/man1/diff.1.html

wc 명령어를 사용해서 파일 또는 입력의 바이트, 문자, 단어 그리고 줄(라인) 수를 세는 방법을 알아보자.

환경

• Linux 기반 시스템
• Bash shell(/bin/bash)

wc 명령어

wc 명령어란?

wc [OPTION]... [FILE]...
wc [OPTION]... --files0-from=F

• wc : 주어지는 파일 또는 표준 입력의 바이트, 문자, 단어 그리고 줄(라인) 수를 출력해주는 명령어입니다.
• wc는 ‘word count’를 의미한다고 합니다.
• ls -al과 함께 폴더와 파일의 수를 알고 싶을때 응용이 가능합니다.

옵션별 사용법

예제에 사용할 파일 작성

• ASCII용 예제

$ cat << EOF > test_ascii.txt
123
abc def hij
lmn opq rs
EOF

$ file test_ascii.txt
test_ascii.txt: ASCII text

• UTF-8용 예제

$ cat << EOF > test_utf.txt
한국어 배워보세요.
감사합니다. 또 봐요!
EOF

$ file test_utf.txt
test_utf.txt: UTF-8 Unicode text

-c, –bytes 옵션

• 파일의 바이트 수를 출력합니다.

$ wc -c test_ascii.txt
27 test_ascii.txt

# You can use it with cat command
$ cat test_ascii.txt | wc -c
27

-m, –chars 옵션

• 문자들의 수를 출력합니다.

$ wc -m test_ascii.txt
27 test_ascii.txt

# You can use it with cat command
$ cat test_ascii.txt | wc -m
27

• ASCII에서는 문자의 수가 곧 바이트의 수지만(문자당 1바이트) 다른 문자 형식에서는 아닐수도 있습니다.

$ wc -m test_ascii.txt
27 test_ascii.txt

$ wc -c test_ascii.txt
27 test_ascii.txt

$ wc -m test_utf.txt
24 test_utf.txt

$ wc -c test_utf.txt
56 test_utf.txt

-l, –lines 옵션

• 줄(라인 또는 개행문자)의 수를 출력합니다.

$ wc -l test_ascii.txt
3 test_ascii.txt

$ cat test_ascii.txt | wc -l
3

• 특정 폴더에서 파일이나 폴더의 수를 알고 싶을 때 ls -al과 같이 사용가능합니다.

$ ls -al | wc -l
9

-w, –words 옵션

• 단어의 수를 출력합니다.

$ wc -w test_ascii.txt
7 test_ascii.txt

$ wc -w test_utf.txt
5 test_utf.txt

참고자료

• http://man7.org/linux/man-pages/man1/wc.1.html
• https://askubuntu.com/questions/803911/wc-c-and-wc-m-command-in-linux

Let’s count number of bytes, characters, words and lines in file or input.

Environment and Prerequisite

• Linux base system
• Bash shell(/bin/bash)

wc command

What is wc command?

wc [OPTION]... [FILE]...
wc [OPTION]... --files0-from=F

• wc : print newline, word, and byte counts for each file or input
• wc stands for ‘word count’
• You can use it with ls -al when count number of files and directories in specific path

Usage with each option

Make sample files for examples

• ASCII sample

$ cat << EOF > test_ascii.txt
123
abc def hij
lmn opq rs
EOF

$ file test_ascii.txt
test_ascii.txt: ASCII text

• UTF-8 sample

$ cat << EOF > test_utf.txt
한국어 배워보세요.
감사합니다. 또 봐요!
EOF

$ file test_utf.txt
test_utf.txt: UTF-8 Unicode text

-c, –bytes option

• print the byte counts.

$ wc -c test_ascii.txt
27 test_ascii.txt

# You can use it with cat command
$ cat test_ascii.txt | wc -c
27

-m, –chars option

• print the character counts.

$ wc -m test_ascii.txt
27 test_ascii.txt

# You can use it with cat command
$ cat test_ascii.txt | wc -m
27

• In ASCII format, the number of bytes and characters are same but some of other formats would be not.

$ wc -m test_ascii.txt
27 test_ascii.txt

$ wc -c test_ascii.txt
27 test_ascii.txt

$ wc -m test_utf.txt
24 test_utf.txt

$ wc -c test_utf.txt
56 test_utf.txt

-l, –lines option

• print the newline counts.

$ wc -l test_ascii.txt
3 test_ascii.txt

$ cat test_ascii.txt | wc -l
3

• You can count number of files and directories in specific path by using it with ls -al.

$ ls -al | wc -l
9

-w, –words option

• print the word counts.

$ wc -w test_ascii.txt
7 test_ascii.txt

$ wc -w test_utf.txt
5 test_utf.txt

Reference

• http://man7.org/linux/man-pages/man1/wc.1.html
• https://askubuntu.com/questions/803911/wc-c-and-wc-m-command-in-linux

tcpdump 명령어를 이용해서 패킷들을 덤프(dump)하고 와이어샤크로 열어보자

환경

• Linux 기반 시스템
• Bash shell(/bin/bash)
• tcpdump 명령어
• Wireshark

tcpdump 명령어

tcpdump 명령어란?

tcpdump [ -AdDefIKlLnNOpqRStuUvxX ] [ -B buffer_size ] [ -c count ]

[ -C file_size ] [ -G rotate_seconds ] [ -F file ]
[ -i interface ] [ -m module ] [ -M secret ]
[ -r file ] [ -s snaplen ] [ -T type ] [ -w file ]
[ -W filecount ]
[ -E spi@ipaddr algo:secret,... ]
[ -y datalinktype ] [ -z postrotate-command ] [ -Z user ] [ expression ]

• tcpdump : 네트워크 인터페이스를 통해 지나가는 패킷들의 내용을 출력해주는 명령어로 여러 옵션을 이용해 패킷들의 오고가는 내용을 볼 수 있다.
• 네트워크 패킷들을 다 조사하는것이기 때문에 root권한이 필요합니다.

특정 인터페이스 패킷들을 파일로 저장하기

기본 사용법

• -i [inferface name] : 패킷들의 내용을 출력하고 싶은 인터페이스의 이름을 옵션으로 줍니다.
• -w [file name] : 패킷들의 내용을 파일로 저장하고 싶을 때 사용하는 옵셥입니다.

tcpdump -i [interface name] -w [file name]

예제

• eth0 인터페이스에 오고가는 패킷들을 test.pcap으로 저장하기
• pcap : 와이어샤크에서 사용하는 파일 형식으로 캡처된 패킷들이 저장되는 파일 형식이다.
• Ctrl + C를 통해서 종료가 가능하다.

$ sudo tcpdump -i eth0 -w test.pcap
tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
860 packets captured
862 packets received by filter
0 packets dropped by kernel

와이어샤크

와이어샤크란?

• 가장 널리쓰이는 네트워크 프로토콜 분석 도구로 아주 작은 레벨까지 네트워크 분석이 가능하며 사실상 표준(de facto)이 된 소프트웨어이다. 상업적 또는 비영리 목적으로 상당히 많이 사용한다.

pcap 형식의 파일을 와이어샤크로 열기

• (방법1) 파일을 드래그 앤드 드롭(Drag-and-drop)을 이용해 열 수 있다.
• (방법2) File-Open에서 파일 선택

주소 값으로 필터링하기

• 특정 IP주소에 해당하는 패킷만 필터링하려면 메뉴에 있는 “Apply a display filter”에 필터를 추가하면 된다.

ip address filter

ip.addr==X.X.X.X
ip.src==X.X.X.X
ip.dst==X.X.X.X

AND condition

(ip.src==X.X.X.X) || (ip.dst==X.X.X.X)

OR condition

(ip.src==X.X.X.X) && (ip.dst==X.X.X.X)

참고자료

• https://linux.die.net/man/8/tcpdump
• https://www.wireshark.org/
• https://stackoverflow.com/questions/4043406/how-to-filter-by-ip-address-in-wireshark/4043596

Dump packets using tcpdump command and open it using wireshark

Environment and Prerequisite

• Linux base system
• Bash shell(/bin/bash)
• tcpdump command
• Wireshark

tcpdump command

What is tcpdump command?

tcpdump [ -AdDefIKlLnNOpqRStuUvxX ] [ -B buffer_size ] [ -c count ]

[ -C file_size ] [ -G rotate_seconds ] [ -F file ]
[ -i interface ] [ -m module ] [ -M secret ]
[ -r file ] [ -s snaplen ] [ -T type ] [ -w file ]
[ -W filecount ]
[ -E spi@ipaddr algo:secret,... ]
[ -y datalinktype ] [ -z postrotate-command ] [ -Z user ] [ expression ]

• tcpdump : prints out a description of the contents of packets on a network interface with various options.
• It scans all packets on network so it needs root privilege

Save specific interface’s packets as file

Basic usage

• -i [inferface name] : give interface name as option
• -w [file name] : give file name as option

tcpdump -i [interface name] -w [file name]

Example

• Save eth0 interface’s packets as test.pcap
• pcap : packet captured file format used in wireshark
• Use Ctrl + C to quit capturing.

$ sudo tcpdump -i eth0 -w test.pcap
tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
860 packets captured
862 packets received by filter
0 packets dropped by kernel

Wireshark

What is wireshark?

• The world’s foremost and widely-used network protocol analyzer.
• It lets you see what’s happening on your network at a microscopic level and is the de facto (and often de jure) standard across many commercial and non-profit enterprises, government agencies, and educational institutions.

Open pcap file using wireshark

• (방법1) Drag-and-drop is also possible
• (방법2) Choose file in File-Open tab

Filtering using ip address

• If you want to filter specific ip address, then add filter to menu’s “Apply a display filter”

ip address filter

ip.addr==X.X.X.X
ip.src==X.X.X.X
ip.dst==X.X.X.X

AND condition

(ip.src==X.X.X.X) || (ip.dst==X.X.X.X)

OR condition

(ip.src==X.X.X.X) && (ip.dst==X.X.X.X)

Reference

• https://linux.die.net/man/8/tcpdump
• https://www.wireshark.org/
• https://stackoverflow.com/questions/4043406/how-to-filter-by-ip-address-in-wireshark/4043596