Well, I have to say up front, this took me a couple of hours to resolve. It appears that this issue is quite common, but I found, literally no complete resolution to this issue anywhere on the Internet. Here is what I tried to do:
I was trying to make a bootable USB drive with BackTrack 5 R3 on it. Here is what I did to get that done:
1. Get unetbootin and the ISO of backtrack.
2. Run unetbootin and select the ISO of backtrack and the USB stick you want to use.
3. Run the program and wait for it to finish.
This worked, except that it wouldnt boot after typing in 'startx". It would just freeze up, black screen, and caps lock blinking steadily. It wouldnt go any further. From my research into this, it appears to be a video driver issue. Im running a Dell Latitude E5410. There appears to be fixes out there, but because Im running this on a USB drive, none of them were permanent fixes. This is the fix that actually got me to realize that the my USB install was ok, and that this was a video driver issue (I found this in the BackTrack forums, posted by p0cTeam):
quote: insert DVD-live, in the grub press TAB to edit boot, you well see something like this file=/cdrom/preseed/ubuntu.see boot=casper initrd=/casper/initrd.gz, add xforcevesa noapic nosplash irqpoll -- after initrd.gz end quote.
Well, that worked, ONCE. There was another fix I found as well, and it appears to be similar in nature, although the syntax was different. It consisted of editing the grub.cfg file. The only problem was that I could not do a 'update-grub' after editing the grub file. Which apparently fixed people's issue IF it was installed on the hard drive of the pc/laptop. Mine wasnt, again, it was on the USB. So for some reason, when I did the update-grub command, it complained to me and it never would write to the grub.cfg file. Bummer.
Well, I found that someone on the Internet mentioned the sys.cfg file. I looked for it in the linux directory, but I couldnt find it anywhere. Another bummer. But, what I did do was boot back into Windows and look at my USB drive and found a file called 'syslinux.cfg'. I opened it up and I edited as follows:
--------
label unetbootindefault
menu label Default
kernel /ubnkern
append initrd=/ubninit file=/cdrom/preseed/custom.seed boot=casper text splash vga=791 xforcevesa noapic noapci nosplash irqpoll --
label ubnentry0
menu label BackTrack Text - Default Boot Text Mode
kernel /casper/vmlinuz
append initrd=/casper/initrd.gz file=/cdrom/preseed/custom.seed boot=casper text splash vga=791 xforcevesa noapic noapci nosplash irqpol --
--------
Highlighted above is what I added. Notice its the same as what p0cTeam said to add, except that it was in the syslinux.cfg file on the USB stick instead of in the grub file on the hard drive.
Ive tested this above and it works well (in my scenario). I appears that there is about 3 variants to this, according to the install you do. Again, mine was a USB, while most appears to address an install on the hard drive. Im not sure how you would edit this on a CD. I hope this helps you.
awk实例操作学习记录
- Published in CentOS 6
- May 31, 2013
awk '/^root/ { print }' /etc/passwd 打印以root开头的行
awk是一种编程语言，用于在linux/unix下对文本和数据进行处理。数据可以来自标准输入、一个或多个文件，或其它命令的输出。它支持用户自定义函数和动态正则表达式等先进功能，是linux/unix下的一个强大编程工具。
awk的处理文本和数据的方式是这样的，它逐行扫描文件，从第一行到最后一行，寻找匹配的特定模式的行，并在这些行上进行你想要的操作。如果没有指定处理动作，则把匹配的行显示到标准输出(屏幕)，如果没有指定模式，则所有被操作所指定的行都被处理。
例子：
一般语法格式
1.# awk '{ print }' /etc/passwd
或# awk '{ print $0 }' /etc/passwd
马上显示/etc/passwd的内容，其中$0变量表示整个当前行
2.# awk '{ print "william" }' /etc/passwd
或# awk '{ print "" }' /etc/passwd
第一条按照/etc/passwd文件中的行数显示william，第二条则显示空行。
字段
3.# awk -F: '{ print $1 }' /etc/passwd
或# awk -F: '{ print $1 $3 }' /etc/passwd
第一条打印输入文件中每一行中出现的第一个字段，第二条则打印第一和第三字段。其中-F:表示指定“：”作为字段分隔符。
4.# awk -F: '{ print $1 " " $3 }' /etc/passwd
# awk -F: '{ print "username: "$1 "\t\tuid: " $3 }' /etc/passwd
例3中输出的结果两个字段之间没有空格，这第一条命令就是加空格，第二条则加了文本标签。
外部脚本
5.# awk -f my.awk /etc/passwd
如果要运行外部的脚本加上-f选项即可，其中my.awk是脚本，/etc/passwd是要操作的文本。
BEGIN和END块
6.BEGIN{
FS=":" 相当于命令行中的-F:
}
{ print $1 }
END{
print "william"
}
awk开始处理文件之前会执行BEGIN块，awk处理文件之后会执行END块。
表达式和块
7.# awk '/root/ { print }' /etc/passwd 打印包含root的行
# awk '/^root/ { print }' /etc/passwd 打印以root开头的行
# awk '/~root/ { print NR NF }' /etc/passwd 有以root结尾的行打印当前记录数和当前记录字段数
# awk '/^root|wang/ { print }' /etc/passwd 打印以root或wang开头的行
# awk '/^[rw]/ { print }' /etc/passwd 打印以字母r或w开头的行
# awk '$1 ~/[0-9]/ { print }' /etc/passwd 打印字段1中以数字结尾的行
# awk -F: '$4 ^/[0-9]/ { print }' /etc/passwd 打印字段4中以数字开头的行
8.# awk -F: '$4==27 { print }' /etc/passwd 打印字段4等于27的行
# awk -F: '$4!=27 || $3>492 { print }' /etc/passwd 打印字段4不等于27或字段3大于492的行
# awk -F: '$4==27 || $3>42 { print $1+10 }' /etc/passwd 假如字段4等于27或者字段3大于42，打印$1+10的值，如果$1不是数字默认为0。
# awk -F: '{print $4==27 ? "ok" : "err"}' /etc/passwd 字段4等于27打印ok，否则打印err
# awk '/^root/,/^bin/' /etc/passwd 打印以root开头到以bin开头的所有行，假如出现第二个以root开头的行，则到下一个yibin开头的行结束或到文件结尾。
条件语句
9.BEGIN{
FS=":"
}
{
if($3==27){
if($4==27){
print "love"
}
}
else if($1 ~/root/) { print "one"} //~是包含，^是不包含
else {
print "others" " " $1}
}
END{
print "william"
}
变量
10.BEGIN {x=0}
/^$/ {x=x+1}
END {print "There are "x" blank lines."}
计算空白行的数量
11.# awk -f my.awk x=8 ./test.c
原来是5，加入x=8后，结果变成了13.另外BEGIN {x=0}可以不要。
12.BEGIN {x="0.01"} //注意变成字符串了
/^$/ {x=x+1}
END {print "There are "x" blank lines."}
执行# awk -f my.awk ./test.c 结果是5.01
字段分隔符
前面设置FS=":"，当然也可以设置多个任意字符为分隔符。
例如：
FS="\t+" +号表示一个或多个
FS="root[0-9][0-9]" 表示root后面接两个数字为分隔符
记录分隔符
NR 记录号 NS 记录分隔符 FS字段分隔符
比如通讯录把名字 地址 电话号码整理为一个记录。其中文本如下
wang
Hunan Chenzhou
123456
li
Guangzhou Zhuhai
654321
13.执行脚本为：BEGIN {
FS="\n"
RS=""
}
{print $1 ","$2","$3}
输出：
wang，Hunan Chenzhou，123456
li，Guangzhou Zhuhai，654321
14.执行脚本为：BEGIN {
FS="\n"
RS=""
OFS="-" 输出字段间隔
ORS="\nnext:\n" 输出记录间隔
}
{print $1, $2, $3}
输出：
wang-Hunan Chenzhou-123456
next:
li-Guangzhou Zhuhai-654321
next:
循环语句
15.BEGIN {
FS="\n"
RS=""
OFS="-"
ORS=""
}
{
x=1
while(x<NF){
print $x "\t" 上面的OFS赋值将不起作用
x++
}
print $NF "\n"}
此外有do while，for，break，continue。
数组
16.
数组下标经常从1开始，而不是0
数组下标字符串化 例如：myarr["name"]="wang" 就算不是字符串也会被看成字符串。
17.delete myarr[1] 删除数组元素1
18.if (wang in myarr) {print "ok"} 查看数组元素
字符串函数
string="Wo men shi ku bi de cheng xu yuan !"
print string[2] 会报错！！
怎么办？
print length(string) 打印字符串长度
print index(string,"men") 查找men在字符串中的位置
print tolower(string) 转换为小写
print toupper(string) 转换为大写
mysbu=substr(string,startpos,maxlen) 在startpos开始截取maxlen这么长的字符
print match(string,/men/),RSTART,RLENGTH 寻找匹配men的位子和长度
sbu(old,new,string) 替换一个
gsbu(old,new,string) 全部替换
num=split("1,2,3,4,5,6",mynum,",") 切开字符串，并将各部分放到整数下标的数组中
函数格式
function 函数名(参数)
{
……
}
