avconv -i INPUT.mp4 -s 640x360 OUTPUT.mp4若影片的聲音是 acc 編碼，上述指令可能會警告你程式的 acc 編碼器還在驗證階段，要求你多加一個參數 ("-strict experimental") 確定你要用這個實驗品：
avconv -i INPUT.mp4 -s 640x360 -strict experimental OUTPUT.mp4若影片太長，你只要前 N 秒，可以加上參數 "-t N"。若只要影像，不要聲音，請參考 去除影片檔聲音的方法。
--- /etc/ssl/openssl.cnf 2012-04-20 00:29:01.000000000 +0800我不確定這樣改有多少影響。建議 key 產生完畢後再改回原來的設定。
+++ /etc/ssl/openssl.cnf 2014-03-14 16:11:58.225994353 +0800
@@ -237,7 +237,7 @@
# extensions.
#basicConstraints = critical,CA:true
# So we do this instead.
-basicConstraints = CA:true
+basicConstraints = CA:false
# Key usage: this is typical for a CA certificate. However since it
# prevent it being used as an test self-signed certificate it is best
avconv -i IN-FILE -vcodec copy -an OUT-FILE其中：
sed -i -e 's:/Annots\[[^]]\+\]::g' FILENAME.PDF上述指令看來很玄，簡單說就是將文件中 "/Annots[....]" 的資料片段都給刪了。
dpkg -i libmp4v2-0_1.6dfsg-0.2ubuntu9_amd64.deb
dpkg -i libmpeg4ip-0_1.6dfsg-0.2ubuntu9_amd64.deb
dpkg -i mpeg4ip-utils_1.6dfsg-0.2ubuntu9_amd64.deb
pcscd: readerfactory.c:965:RFInitializeReader() Open Port 0x200000 Failed (USB:0CA6/0010:LIBUDEV:0:/DEV/BUS/USB/004/002)
pcscd: readerfactory.c:275:RFAddReader() CASTLES EZ100PU init failed.
pcscd: hotplug_libudev.c:377:HPAddDevice() Failed adding USB device: CASTLES EZ100PU
這問題有兩個解法：第一個較簡單，第二個較安全。# DO NOT start the daemon on startup解法二是較安全的方式，是以使用者身份動態執行 pcscd，但你必須賦予這台讀卡機特殊的權限。作法是新建一個檔案：/etc/udev/rules.d/92-pcscd-ccid.rules。內容如下：
# comment the line to have the same behavior as in version < 1.6.0
#exit 0
# If not adding the device, go away注意上面的 idVendor 和 idProduct 必須對應到讀卡機的 USB ID。你可用 lsusb 查出 USB ID，譬如：
ACTION!="add", GOTO="pcscd_ccid_rules_end"
SUBSYSTEM!="usb", GOTO="pcscd_ccid_rules_end"
ENV{DEVTYPE}!="usb_device", GOTO="pcscd_ccid_rules_end"
# Castles Technology Co., Ltd EZUSB PC/SC Smart Card Reader
ATTRS{idVendor}=="0ca6", ATTRS{idProduct}=="0010", GROUP="pcscd"
# All done
LABEL="pcscd_ccid_rules_end"
Bus 003 Device 003: ID 0ca6:0010 Castles Technology Co., Ltd EZUSB PC/SC Smart Card Reader改完後 sudo service udev restart，應該就大功告成了。
awk 'BEGIN { while (1) printf("%c", 255) }' \PS: 你問我為什麼要產生這種檔案？是為了填補 flash ROM 的內容。Flash ROM 的空的狀態就是 0xFF。
| dd of=allone.dat bs=1 count=1024
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 8.10
Release: 8.10
Codename: intrepid
No LSB modules are available.
Distributor ID: Debian
Description: Debian GNU/Linux 4.0 (etch)
Release: 4.0
Codename: etch
LSB Version: :core-3.1-ia32:core-3.1-noarch:graphics-3.1-ia32:graphics-3.1-noarch執行 ls /etc/*release 再執行 cat /etc/*release
Distributor ID: CentOS
Description: CentOS release 5.2 (Final)
Release: 5.2
Codename: Final
grep -r STRING *這兩個指令很好用。但是遇到 Subversion 的 working copy 時，就會受到 .svn 目錄的干擾。所幸這兩個指令都提供排除非必要目錄的方法：
diff -ur DIR1 DIR2
grep --exclude-dir=.svn -r STRING *
diff -x .svn -ur DIR1 DIR2
alias grep='grep --exclude-dir=.svn'
alias diff='diff -x .svn'
