My PS1 in ~/.bashrc

export PS1="\[\e[00;30m\]\u@\h:\w\\$ \[\e[0m\]"

user@hostname:directory $or#

->

root@rhel7:/lib/systemd/system# 

[lawrence@rhel7 tmp]$ 

How to enable vncserver on CentOS7/RHEL7

CentOS7/RHEL7 改用了systemd取代了SysVinit，因此我必須把這幾年已經還給天地的Linux重新拿出來研究一番，否則真的跟不上時代了！那就先從學習systemd開始吧！


Case: How can I enable vncserver at boot?

Steps:
1. Install vnc:

#yum install tigervnc*

2. 建立vnc user:

以某個user來執行vncserver之後，在user家目錄中有這個/.vnc/xstartup檔案就可以了，當然passwd也是會一起產生的。

以上與CentOS6/RHEL6無異。


3. 修改vnc config:

開啟/lib/systemd/system/vncserver@.service
修改[service]這個field如下：
[Service]
Type=forking
# Clean any existing files in /tmp/.X11-unix environment
ExecStartPre=/bin/sh -c '/usr/bin/vncserver -kill > /dev/null 2>&1 || :'
ExecStart=/sbin/runuser -l root -c "/usr/bin/vncserver"
ExecStop=/bin/sh -c '/usr/bin/vncserver -kill > /dev/null 2>&1 || :'

用root啟動vncserver不是一個好習慣.....


4. daemon-reload:

修改unit(service)的configuration後，必需讓systemd知道，所以我要執行 systemctl daemon-reload昭告天下。

5. 手動啟動vncserver:

systemctl start vncserver@multi-user

6. 開機啟動vncserver:

systemctl enable vncserver@multi-user

解決facility與severity在LogAnalyzer是空白的問題

最近實作中也碰到了這個問題，解決的方法如下：
http://wiki.rsyslog.com/index.php/Fix_blank_Facility_and_Severity_columns_in_loganalyzer

補充:
如何改變syslog到Rsyslog format23? 原文並沒有提到唷！這邊幫忙補充一下。

只需要一個步驟，那就是修改LogAnalyzer的config.php，把LogLineType從syslog改成syslog23如下：

$CFG['Sources']['Source2']['LogLineType'] = 'syslog23';

How to turn on wireless monitor mode to sniffer 802.11 wireless frame on OSX 10.9?

Install:

Step1. Install XQartz(X11) for OSX 10.6 or later (http://xquartz.macosforge.org/landing/)
Step2. Logout and login OSX by Admin account.
Step3. Install Wireshark for OSX 10.6 and later Intel 64 bit (http://www.wireshark.org/download.html)
Step4. Launch Wireshark and chose XQartz as X11 environment.
Step5. Turn on monitor mode -> http://ask.wireshark.org/questions/26270/how-to-turn-on-monitor-mode-on-mac-osx-1075

Specify channel for 2.4G or 5G radio:

Step1. sudo ln -s /System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport /usr/sbin/airport
Step2. sudo airport -z #disassociates you card from the current network
Step3. sudo airport --channel= ["channel you want to switch to"] #sets the channel the card monitors on

為何tail -f | grep "" >> 檔案 然後發現資料不完全? missing line?

昨天被同事問到這個問題，由於小弟智力有限一時間竟無法理解，然而今天找到答案了，原來是libc對於這種 pipe的結構不會自動去清除buffer，所以一旦buffer滿了(4KB by default)那接下來的資料就無法繼續傳給pipe之後來處理，所以就會missing line囉，解決的方法就是手動自行清除buffer如下以避免爆炸。

tail -f | grep "pattern" --line-buffered >> /tmp/log &

How does snmptrap work on Linux?

在此簡單記錄下如何設定CentOS接收snmp v2與v3的trap event.

Steps:
1. 安裝net-snmp。

2. 確定snmptrapd已經安裝於系統。

3. 匯入mibs files：

先確定mibs的目錄:
[root@localhost ~]# net-snmp-config --default-mibdirs
/root/.snmp/mibs:/usr/share/snmp/mibs
可以看到我的mibs可以放在/root/.snmp/mibs or /usr/share/snmp/mibs，在此我選擇放在/usr/share/snmp/mibs。

4. 設定snmptrapd可以接收snmp v2與v3的trap event：

開啟並編輯[root@localhost mibs]# vi /etc/snmp/snmptrapd.conf 如下：
#SNMP v2 with community as public
disableAuthorization no
authCommunity log,execute,net public
# SNMP v3 with user as admin and passphase as aaaaaaaa
createUser admin MD5 aaaaaaaa DES aaaaaaaa
authUser log,execute,net admin

5. 不以daemon的方式啟動snmptrapd：

[root@localhost mibs]# snmptrapd -m all -c /etc/snmp/snmptrapd.conf -Lo -f
NET-SNMP version 5.3.2.2
-m all -> 讀入所有的mibs files
-c -> 預設的configuration file
-Lo -> 輸出到基本output
-f -> do not fork from the shell
這邊你會看到snmp trap event會輸出至螢幕，方便debug用。

6. 以daemon的方式啟動snmptrapd：

[root@localhost mibs]# /etc/init.d/snmptrapd start
正在啟動 snmptrapd:                                        [  確定  ]
而這裡你將會看到snmp trap event會被寫入到/var/log/messages。

How to enable auth details in FreeRADIUS log?

Here to describe how to enable detail auth information and authentication requests to the log file in FreeRADIUS.

FreeRADIUS 1.x:

Open and edit /etc/raddb/radiusd.conf to set:
log_auth = yes
auth_log
detail auth_log {
                detailfile = ${radacctdir}/%{Client-IP-Address}/auth-detail-%Y%m%d
                #
                #  This MUST be 0600, otherwise anyone can read
                #  the users passwords!
                detailperm = 0600
         }

FreeRADIUS 2.x:

Open and edit /etc/raddb/radiusd.conf to set:
auth = yes
Open and edit /etc/raddb/sites-available/default to set:
auth_log

How can I allow IP protocol 47 (gre) via iptables to connect a GRE GW?

Topology:

GRE GW1 ----- Switch -----(eth0)Linux NAT Router(eth1) ----- Switch ----- GRE GW2

To configure IP protocol 47 to GRE GW on NAT Router below:

# iptables -t nat -A PREROUTING -i eth0 -p gre -j DNAT --to-destination 10.10.2.186  

Where 10.10.2.186 is GRE GW2's IP.

To configure L2oGRE on Linux:

# modprobe ip_gre
# ip link add link gre0 name tunnel0 type gretap remote 192.168.0.1 local 10.10.2.186
# ip link set tunnel0 up
# brctl addbr br0
# ip link set br0 up
# ip link set eth2 up
# brctl addif br0 tunnel0
# brctl addif br0 eth2

Set http/https proxy server in Linux CLI

HTTP:

# export http_proxy="http://10.10.10.254:8080"

HTTPs:

# export https_proxy="https://10.10.10.254:8080"

Where 10.10.10.254 is the IP of Proxy Server, and 8080 is port number.

Remove:

# unset http_proxy
# unset https_proxy

Afterward you can use curl to verify.

Howto TACACS+ on CentOS6.x

Here to describe howto install/configure TACACS+ on CentOS6.x on step by step.

Step1. Download rpm:

wget ftp://ftp.muug.mb.ca/mirror/redhat/contrib/libc6/i386/tac_plus-4.0.3-2.i386.rpm

Step2. Install:

rpm -ivh tac_plus-4.0.3-2.i386.rpm

Step3. Configure user in TACACS+:

vi /etc/tacacs/tac_plus.cfg
# Created by Devrim SERAL(devrim@tef.gazi.edu.tr)
# It's very simple configuration file
# Please read user_guide and tacacs+ FAQ to more information to do more
# complex tacacs+ configuration files.
#
# Put your NAS key below
key = "testing123"
# Use /etc/passwd.loc file to do authentication
# it's must be in passwd file format. So you must mix shadow-passwd files to do it
#default authentication = file /etc/passwd.loc
user = lawrence {        login = cleartext 123456}

# Where is the accounting records to go
accounting file = /var/log/tacacs.log
# Permit all authorization request
default authorization = permit
# End config file

# The user lawrence with password 123456 will be created.

Step4. Start TACACS+ daemon:

[root@server1 tmp]# /etc/init.d/tacacs start
Starting tacacs+:
[root@server1 tmp]# netstat -tupln | grep 49
tcp        0      0 0.0.0.0:49                  0.0.0.0:*                   LISTEN      9027/tac_plus

Done~

Update1, small snapshot from user guide:


At the service authorization level i.e. inside the braces of a
service declaration, arguments in an authorization request are
processed according to the algorithm described later. Some actions
when authorizing services (e.g. when matching attributes are not
found) depend on how the default is configured. The following
declaration changes the default from deny to permit for this user and
service.

user = lol {
    service = exec {
        default attribute = permit
    }
}

Howto debug:

DEBUGGING A RUNNING SERVER
--------------------------

There is a myriad of debugging values that can be used in conjunction
with the -d flag to produce debugging output in /var/tmp/tac_plus.log.

For example, starting the daemon with

        tac_plus -C CONFIG -d 16

will put authentication debugging into /var/tmp/tac_plus.log. You can
view this information by using the tail command.

        tail -f /var/tmp/tac_plus.log

See the man page for more information.

增加FreeRADIUS的listen port

預設FreeRADIUS的listen port為1812(認證)與1813(計費)，但是FreeRADIUS允許我們可以多bind幾個port來使用。

測試版本: CentOS 5.8/FreeRADIUS 1.1.3-1.6.el5

Steps:
1. 確定目前只有1812/1813在使用，1814/1815無任何daemon使用，等會將設定1814為Auth而1815為ACCT。

[root@server1 raddb]# netstat -tupln | grep 1812
udp        0      0 0.0.0.0:1812                0.0.0.0:*                               7300/radiusd      
[root@server1 raddb]# netstat -tupln | grep 1813
udp        0      0 0.0.0.0:1813                0.0.0.0:*                               7300/radiusd      
[root@server1 raddb]# netstat -tupln | grep 1814
[root@server1 raddb]# netstat -tupln | grep 1815

2. 開啟/etc/raddb/radiusd.conf，並新增listen ports 1814與1815。

listen {
 ipaddr = *
 port=1814
 type=auth
}
listen {
 ipaddr = *
 port=1815
 type=acct
}

3. 重新啟動FreeRADIUS:

[root@server1 raddb]# /etc/init.d/radiusd restart
正在停止 RADIUS 伺服器:                                    [  確定  ]
正在啟動 RADIUS 伺服器: Thu Feb  7 13:31:06 2013 : Info: Starting - reading configuration files ...
                                                           [  確定  ]

4. 檢查1812, 1813, 1814, 1815為FreeRADIUS所使用。

[root@server1 raddb]# netstat -tupln | grep 1812
udp        0      0 0.0.0.0:1812                0.0.0.0:*                               7347/radiusd      
[root@server1 raddb]# netstat -tupln | grep 1813
udp        0      0 0.0.0.0:1813                0.0.0.0:*                               7347/radiusd      
[root@server1 raddb]# netstat -tupln | grep 1814
udp        0      0 0.0.0.0:1814                0.0.0.0:*                               7347/radiusd      
[root@server1 raddb]# netstat -tupln | grep 1815
udp        0      0 0.0.0.0:1815                0.0.0.0:*                               7347/radiusd   

大功告成！

CentOS 5.9 has released!

CentOS 5.9 釋出了，明天來update。
http://www.tecmint.com/how-to-upgrade-from-centos-5-x-to-centos-5-9/

Linux有Terminator，OSX呢？

Terminator在Linux上可說是神兵利器，絕對是工程師的最愛，那麼OSX呢? 唉，原生的終端機真的是跟不上時代...... 好在有iTerm2可以用，真是棒呀！現在我只能說13"的MBP螢幕有點小。:p

Disable IPv6 in Mac OSX 10.7

如下圖在OSX10.7裡面的網路設定，針對IPv6並沒有關閉的選項，搜尋了一下可以用command暫時將它關閉起來。

For Ethernet:

networksetup -setv6off Ethernet

For Wireless:

networksetup -setv6off Wi-Fi

Bonjour browser on OSX

You can use mDNS or Bonjour browser to query DNS-SD on OSX as following:

• Browser service:

mDNS -B                (Browse for services instances)
MBP:~ lawrence$ mDNS -B _sftp-ssh._tcp.
Browsing for _sftp-ssh._tcp.
Talking to DNS SD Daemon at Mach port 5891
Timestamp     A/R Flags Domain                   Service Type             Instance Name
12:18:11.060  Add     0 local.                   _sftp-ssh._tcp.          MBP

• Look up a service:

mDNS -L           (Look up a service instance)
MBP:~ lawrence$ mDNS -L "MBP" _sftp-ssh._tcp. .
Lookup MBP._sftp-ssh._tcp.local
Talking to DNS SD Daemon at Mach port 5891
12:18:54.882  Service can be reached at   10.10.2.7      :22
12:18:54.882  FE80:0000:0000:0000:3E07:54FF:FE35:5093%en0:22
12:18:54.883  3001:0288:0000:0000:3E07:54FF:FE35:5093%en0:22

• Bonjour browser:

References:

http://en.wikipedia.org/wiki/Multicast_DNS

Bonjour browser
How to reset the DNS cache on OSX

Bonjour browser for Windows and Android

mDNS repeater

DHCP Server某網段的IP range被用完了該怎麼辦？

做實驗時不小心把某個網段的IP scope用完了，距離release時間有一天，影響到新的client拿不到IP了，靈機一動就想把它手動砍掉吧！不過我要對付的是整個IP scope，嘿嘿～派出sed一行指令就結束了。

Steps:

1. dhcpd的lease table是放在/var/lib/dhcpd/dhcpd.leases

2. 檢查一下格式:

lease 10.10.6.125 {
  starts 2 2012/10/16 22:12:53;
  ends 3 2012/10/17 22:12:53;
  tstp 3 2012/10/17 22:12:53;
  binding state active;
  next binding state free;
  hardware ethernet b8:ac:6f:21:53:ec;
  uid "\001\270\254o!S\354";
  client-hostname "D129252S";
}

10.10.6這個range被fake DHCP client用完了，所以我要把它們手動通通砍掉。

3. Sed:

sed -i "/10.10.6/,/}/d" /var/lib/dhcpd/dhcpd.leases

4. 重啟DHCP Server:

# /etc/init.d/dhcpd restart

參考: http://en.kioskea.net/faq/1451-sed-delete-one-or-more-lines-from-a-file

Install Monitorix on CentOS

Monitorix是一套free, open的套件能幫助系統管理者觀察主機的各種狀況，比如網路的流量，磁碟的使用率與服務的負載等等。安裝與配置的方法則是出乎意料的簡單。

Step1. Installation:

# yum install httpd rrdtool rrdtool-perl perl-libwww-perl perl-MailTools perl-MIME-Lite perl-CGI perl-DBI perl-XML-Simple

# rpm -ivh http://www.monitorix.org/monitorix-n.n.n-1.noarch.rpm
(where n.n.n is the latest version,2.6.0 for example)

Step2. Configuration:

Configure file is in /etc/monitorix.conf
Apache configure file is in /etc/httpd/conf.d/monitorix.conf, and you need to configure it allow connect to Monitorix from any where.

Step3. Restart service:

# /etc/init.d/monitorix start && chkconfig monitorix on
# /etc/init.d/httpd restart && chkconfig httpd on

Step4. Access:
http://X.X.X.X/monitorix/
(Where X.X.X.X is your IP address)

升級OpenSUSE12.2

剛剛把OpenSUSE12.1升級到了12.2，先來說說第1印象吧。

1. 改用了Systemd取代Sys V，所以感覺上開機變更快了。
2. 字型變更漂亮。
3. DeadBeef運作良好，不受升級影響。
4. aMule運作良好，不受升級影響。
5. Terminator運作良好，不受升級影響。

問題：

1. 音效輸出不會自動切換，比如當插入耳機後，喇叭還是有輸出。
2. Google-Chrome需要重新安裝。
3. PPS不能播放，可能需要重新安裝。
4. Tools bar看不到目前的輸入法。
5. 無法針對RAR檔案解壓縮。

剛升級完，繼續測試中。

How to upgrade?

How to be a Multicast Video stream Server in Linux

透過VLC這套軟體，可以在Linux建立支援multicast的媒體串流播放器，以下簡單的記錄IPv4與IPv6的建立與播放的方法：

1. IPv4:
- 切換至non-root user.
- 開啟console.
- 執行以下的命令：
vlc -vvv 111755131.mov -L --sout '#duplicate{dst=rtp{mux=ts,dst=239.1.1.1,port=5004,sdp=sap://,name="TestStream"}}'

111755131.mov 是欲播放的檔案。
239.1.1.1 with port 5004 是multicast的IPv4 address與port number.


2. IPv6:
步驟跟IPv4都一樣，只是將IP改成v6的格式如下:
vlc -vvv 111755131.mov -L --sout '#duplicate{dst=rtp{mux=ts,dst=[ff08::114],port=5004,sdp=sap://,name="TestStream"}}'


VLC Client:
- IGMP v2: Media::Open Network Stream:: rtp://@239.1.1.1:5004

- IGMP v3: Media::Open Network Stream:: rtp://10.10.10.10@239.1.1.1:5004

- MLD: Media::Open Network Stream:: rtp://@[ff08::114]:5004

Set IGMP version in Windows

Latency when displaying a live RTP stream

帽客的愛車 VW Tiguan

Tiguan結合了Tiger與Lguana -> OSX+OpenSUSE? 所以我對它情有獨鍾 :) 別來亂了，這台車是我老婆選的。但是它真的是台好車唷！