when a man love(s) a woman...

1. 개인키 생성
$ openssl genrsa -out private_key.pem -3 2048
  -3: Exponent 지정 기본값=65537
  2048: 키 길이
$ cat private_key.pem
-----BEGIN RSA PRIVATE KEY-----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-----END RSA PRIVATE KEY-----

2. 개인키를 이용한 공개키 생성
$ openssl rsa -in private_key.pem -out public_key.pem -pubout
$ cat public_key.pem
-----BEGIN PUBLIC KEY-----
MIIBIDANBgkqhkiG9w0BAQEFAAOCAQ0AMIIBCAKCAQEA0jq/cYwTBOWZgQ/kX2L7
XjzKTRPPmJtw4I+UUErrUtGuMre+5J4Wikoa1QLwWj/EllR7x+rZRa5tCbKyQWxT
3TRGfbUUOMrpjDzIE9rrGK8gGat+e3OHTsOnk1tqRUeednSCVyTszOQomTjSQiTe
6UhCul4okAPHBgd6yeq8B/wjwFkSbFmMHtnpMTmbm8Iui70Cl3TJ0WEBnThwJCwy
c+jNZPJGOf0t6OaNmJGZ1aKKUZsQjXRvIR1v1PuvWWwfNquGaiX3iP0eHLprD9Aj
3O7p1OAd6StmRreKgM6awhGtJCkysJk2xdqvMuuDUuliPjSwZYGFtcw5Opm7Ir7G
ywIBAw==
-----END PUBLIC KEY-----

3. pem파일을 rsa der로 변환
$openssl rsa -pubin -text -in public_key.pem > out.pub
$ cat out.pub
Public-Key: (2048 bit)
Modulus:
    00:d2:3a:bf:71:8c:13:04:e5:99:81:0f:e4:5f:62:
    fb:5e:3c:ca:4d:13:cf:98:9b:70:e0:8f:94:50:4a:
    eb:52:d1:ae:32:b7:be:e4:9e:16:8a:4a:1a:d5:02:
    f0:5a:3f:c4:96:54:7b:c7:ea:d9:45:ae:6d:09:b2:
    b2:41:6c:53:dd:34:46:7d:b5:14:38:ca:e9:8c:3c:
    c8:13:da:eb:18:af:20:19:ab:7e:7b:73:87:4e:c3:
    a7:93:5b:6a:45:47:9e:76:74:82:57:24:ec:cc:e4:
    28:99:38:d2:42:24:de:e9:48:42:ba:5e:28:90:03:
    c7:06:07:7a:c9:ea:bc:07:fc:23:c0:59:12:6c:59:
    8c:1e:d9:e9:31:39:9b:9b:c2:2e:8b:bd:02:97:74:
    c9:d1:61:01:9d:38:70:24:2c:32:73:e8:cd:64:f2:
    46:39:fd:2d:e8:e6:8d:98:91:99:d5:a2:8a:51:9b:
    10:8d:74:6f:21:1d:6f:d4:fb:af:59:6c:1f:36:ab:
    86:6a:25:f7:88:fd:1e:1c:ba:6b:0f:d0:23:dc:ee:
    e9:d4:e0:1d:e9:2b:66:46:b7:8a:80:ce:9a:c2:11:
    ad:24:29:32:b0:99:36:c5:da:af:32:eb:83:52:e9:
    62:3e:34:b0:65:81:85:b5:cc:39:3a:99:bb:22:be:
    c6:cb
Exponent: 3 (0x3)
-----BEGIN PUBLIC KEY-----
MIIBIDANBgkqhkiG9w0BAQEFAAOCAQ0AMIIBCAKCAQEA0jq/cYwTBOWZgQ/kX2L7
XjzKTRPPmJtw4I+UUErrUtGuMre+5J4Wikoa1QLwWj/EllR7x+rZRa5tCbKyQWxT
3TRGfbUUOMrpjDzIE9rrGK8gGat+e3OHTsOnk1tqRUeednSCVyTszOQomTjSQiTe
6UhCul4okAPHBgd6yeq8B/wjwFkSbFmMHtnpMTmbm8Iui70Cl3TJ0WEBnThwJCwy
c+jNZPJGOf0t6OaNmJGZ1aKKUZsQjXRvIR1v1PuvWWwfNquGaiX3iP0eHLprD9Aj
3O7p1OAd6StmRreKgM6awhGtJCkysJk2xdqvMuuDUuliPjSwZYGFtcw5Opm7Ir7G
ywIBAw==
-----END PUBLIC KEY-----

//1. 파일압축(해제) ================================================================
1) zip
- 압축하기
zip -rF (압축파일명).zip (압축할 폴더 또는 파일)
    r: 서브 디렉터리 까지 압축
    F: 한글 이름을 가진 파일까지 압축

zip filename.zip ./*     #현재 폴더에 전부를 압축할때 "./*"는 현재 폴더 전부를 의미
zip -r filename.zip ./*  #현재 폴더 하위에있는 폴더 포함하여 압축
- 압축 풀기
unzip filename.zip
unzip filename.zip -d /foldername/

2) tar
- 옵션
    c: 압축
    z: tar 압축후 gzip압축
    v: verbose 압축과정을 출력
    p: 소유권등 퍼미션을 그대로 유지
    f: 내가 지정한 파일명으로 압축
- 압축하기
$ tar cf [압축파일명.tar] [압축할 파일 또는 디렉토리]
[root@localhost~]# tar cvf ksnet.tgz /ksnet/                    #파일압축.
[root@localhost~]# tar czvpf filename.tar.gz public_html/   #tar.gz파일로 압축(퍼미션유지)
- 압축 풀기
$ tar xf [압축파일명.tar]
$ tar -xvf filename.tar -C /folder/dest_folder_name/               #지정된 위치에 압축풀기
[root@localhost~]# tar xzvpf filename.tar.gz -C public_html/   #public_html/에 권한을 유지하며 압축풀기

* tar 와 tar.gz 파일압축의 다른점 : 옵션에서 z 차이(z가 있으면 압축 없으면 묶음)

3) tar.gz
- 압축하기
$ tar zcf [압축파일명.tar.gz] [압축할 파일/디렉토리]
$ tar -czvf 압축파일명.tar.gz 압축할파일/폴더1 압축할파일/폴더2 압축할파일/폴더3 ...
$ tar -czvf images.tar.gz ./folder/a1.jpg ./folder/a2.jpg ./folder/a3.jpg
$ tar -czvf --exclude=./folder/filename.jpg tarname.tar.gz ./folder    #예외 압축
- 압축 풀기
$ tar xfz [압축파일명.tar.gz]
$ tar -xzvf 압축되어있는파일명.tar.gz
$ tar -zxvf filename.tar.gz -C /folder/dest_folder_name/    #지정된 위치에 압축풀기
* 옵션 : 'z' 옵션이 gz 파일 압축 하기/풀기 옵션

4) tar.bz2(압축률이 가장높음)
- 압축하기
$ tar jcvf [압축파일명.tar.bz2] [압축할 파일/디렉토리]
- 압축 풀기
$ tar jxvf [압축파일명.tar.bz2]
$ tar -jxvf filename.tar.bz2 -C /folder/dest_folder_name/
$ tar jxvpf toolchain_160921.tar.bz2
* 옵션 : 'j' 옵션이 bz2 파일 압축 하기/풀기 옵션
============================================================================

//2. Linux 32bit or 64bit check ========================================================
1) getconf LONG_BIT
→ 32 = 32bit
→ 64 = 64bit
2) arch
→ x86_64 = 64bit
→ i386 or i686 = 32bit (i386=old)
3) uname -m
→ x86_64 = 64bit
→ i386 or i686 = 32bit (i386=old)
4) echo $HOSTTYPE
→ x86_64 = 64bit
→ i386 or i686 = 32bit (i386=old)
5) lscpu
→ Architecture: i686 = 32bit
→ Architecture: x86_64 = 64bit
============================================================================

//3. scp 명령어 사용 ===============================================================
scp [file] [계정@host:경로]
ex scp test.zip acount@domain.com:/home/acount/directory/
acount@domain.com's password:_ //계정비밀번호 입력
============================================================================

//4. 저장용량 확인 ================================================================
[root@localhost~]# df -h    #기본값(df -k)은 KB단위로 출력   #df -h //MB단위로 출력
[root@localhost~]# du -sh /home/directoryname/        #디렉토리 사용량 확인
============================================================================

//5. symbolic link =================================================================
[root@localhost~]# ln -s /home/directory/file symboliclinkfile //symbolic link create
[root@localhost~]# rm symboliclinkfile //sysbolic link remove
============================================================================

1. JDK다운로드 http://www.oracle.com/technetwork/java/index.html
→ JavaSE → JavaSE 8u 201 클릭 및 다운로드
버전선택시 최신버전은 사용하지 말것 어떤버그가 있을지 모름 대신 Oracle strongly recommends 문구 확인 해서 추천하는 버전을 사용할 것.

2. 환경변수 설정
제어판 → 시스템 → 고급시스템 설정 → 고급 (또는 윈도우+r → sysdm.cpl ,3 입력) → 환경변수 클릭
1) 시스템 변수 설정
   변수명: JAVA_HOME / 변수값: 설치경로[C:\Program Files\Java\jdk1.8.0_201]
   변수명: CLASSPATH / 변수값: [.;%JAVA_HOME%\lib\tools.jar]
2) 사용자 변수 Path 추가
   변수값: [%JAVA_HOME%\bin]

3. 정상설치 확인
Windows+R → cmd¶
C:\WINDOWS\system32>java -version¶
java version "1.8.0_201"
Java(TM) SE Runtime Environment (build 1.8.0_201-b09)
Java HotSpot(TM) 64-Bit Server VM (build 25.201-b09, mixed mode)

C:\WINDOWS\system32>javac -version¶
javac 1.8.0_201