[命令集3.7] 立刻创建swap分区
假设你需要很多的 swap 空间 (即刻),如一个 2GB 文件 /swap2gb (只限 Linux)。
# dd if=/dev/zero of=/swap2gb bs=1024k count=2000 # mkswap /swap2gb # 创建交换区 # swapon /swap2gb # 激活这个 swap。现在可以使用了 # swapoff /swap2gb # 当使用完毕,释放这个 swap # rm /swap2gb |
[linux秘笈30]. PS2 - 持续交互的提示符
A very long command can be broken down to multiple lines by giving \ at the
end of the line. The default interactive prompt for a multi-line command is
“> “. Let us change this default behavior to display “continue->” by using PS2
environment variable as shown below.
ramesh@dev-db ~> myisamchk –silent –force –fast –
update-state \
> –key_buffer_size=512M –sort_buffer_size=512M \
> –read_buffer_size=4M –write_buffer_size=4M \
> /var/lib/mysql/bugs/*.MYI
[Note: This uses the default ">" for continuation
prompt]
ramesh@dev-db ~> export PS2=”continue-> ”
ramesh@dev-db ~> myisamchk –silent –force –fast –
update-state \
continue-> –key_buffer_size=512M –
sort_buffer_size=512M \
continue-> –read_buffer_size=4M –write_buffer_size=4M
\
continue-> /var/lib/mysql/bugs/*.MYI
[Note: This uses the modified "continue-> " for continuation prompt]
I found it very helpful and easy to read, when I break my long commands into
multiple lines using \. I have also seen others who don’t like to break-up long
commands.
[命令集3.4]系统挂载点/磁盘使用情况
# mount | column -t # 显示系统已挂载分区情况 # df # 显示磁盘剩余空间和挂载的设备 # cat /proc/partitions # 显示所有设备的所有分区(Linux) |
[Linux秘笈28].显示用户连接时间
Ac command will display the statistics about the user’s connect time.
Connect time for the current logged in user
With the option –d, it will break down the output for the individual days. In
this example, I’ve been logged in to the system for more than 6 hours today.
On Dec 1st, I was logged in for about 1 hour.
$ ac –d Dec 1 total 1.08 Dec 2 total 0.99 Dec 3 total 3.39 Dec 4 total 4.50 Today total 6.10 |
Connect time for all the users
To display connect time for all the users use –p as shown below. Please note
that this indicates the cumulative connect time for the individual users.
$ ac -p john 3.64 madison 0.06 sanjay 88.17 nisha 105.92 ramesh 111.42 total 309.21 |
Connect time for a specific user
To get a connect time report for a specific user, execute the following:
$ ac -d sanjay Jul 2 total 12.85 Aug 25 total 5.05 Sep 3 total 1.03 Sep 4 total 5.37 Dec 24 total 8.15 Dec 29 total 1.42 Today total 2.95 |
[命令集3.3]FreeBSD下的启动引导
如果新内核不能引导,要引导一个旧内核,停止启动倒计时,做如下动作:
# unload # load kernel.old # boot |
[linux秘笈27]Diff命令
diff命令，通常用来比较两个文件的差别，命令的输出比较隐晦，不能直接阅读。使用方法
Syntax: diff [options] file1 file2 |
具体的使用方法
jcai@jcai-notebook:~$ diff --help Usage: diff [OPTION]... FILES Compare files line by line. -i --ignore-case Ignore case differences in file contents. --ignore-file-name-case Ignore case when comparing file names. --no-ignore-file-name-case Consider case when comparing file names. -E --ignore-tab-expansion Ignore changes due to tab expansion. -b --ignore-space-change Ignore changes in the amount of white space. -w --ignore-all-space Ignore all white space. -B --ignore-blank-lines Ignore changes whose lines are all blank. -I RE --ignore-matching-lines=RE Ignore changes whose lines all match RE. --strip-trailing-cr Strip trailing carriage return on input. -a --text Treat all files as text. -c -C NUM --context[=NUM] Output NUM (default 3) lines of copied context. -u -U NUM --unified[=NUM] Output NUM (default 3) lines of unified context. --label LABEL Use LABEL instead of file name. -p --show-c-function Show which C function each change is in. -F RE --show-function-line=RE Show the most recent line matching RE. -q --brief Output only whether files differ. -e --ed Output an ed script. --normal Output a normal diff. -n --rcs Output an RCS format diff. -y --side-by-side Output in two columns. -W NUM --width=NUM Output at most NUM (default 130) print columns. --left-column Output only the left column of common lines. --suppress-common-lines Do not output common lines. -D NAME --ifdef=NAME Output merged file to show `#ifdef NAME' diffs. --GTYPE-group-format=GFMT Similar, but format GTYPE input groups with GFMT. --line-format=LFMT Similar, but format all input lines with LFMT. --LTYPE-line-format=LFMT Similar, but format LTYPE input lines with LFMT. LTYPE is `old', `new', or `unchanged'. GTYPE is LTYPE or `changed'. GFMT may contain: %< lines from FILE1 %> lines from FILE2 %= lines common to FILE1 and FILE2 %[-][WIDTH][.[PREC]]{doxX}LETTER printf-style spec for LETTER LETTERs are as follows for new group, lower case for old group: F first line number L last line number N number of lines = L-F+1 E F-1 M L+1 LFMT may contain: %L contents of line %l contents of line, excluding any trailing newline %[-][WIDTH][.[PREC]]{doxX}n printf-style spec for input line number Either GFMT or LFMT may contain: %% % %c'C' the single character C %c'\OOO' the character with octal code OOO -l --paginate Pass the output through `pr' to paginate it. -t --expand-tabs Expand tabs to spaces in output. -T --initial-tab Make tabs line up by prepending a tab. -r --recursive Recursively compare any subdirectories found. -N --new-file Treat absent files as empty. --unidirectional-new-file Treat absent first files as empty. -s --report-identical-files Report when two files are the same. -x PAT --exclude=PAT Exclude files that match PAT. -X FILE --exclude-from=FILE Exclude files that match any pattern in FILE. -S FILE --starting-file=FILE Start with FILE when comparing directories. --from-file=FILE1 Compare FILE1 to all operands. FILE1 can be a directory. --to-file=FILE2 Compare all operands to FILE2. FILE2 can be a directory. --horizon-lines=NUM Keep NUM lines of the common prefix and suffix. -d --minimal Try hard to find a smaller set of changes. --speed-large-files Assume large files and many scattered small changes. -v --version Output version info. --help Output this help. FILES are `FILE1 FILE2' or `DIR1 DIR2' or `DIR FILE...' or `FILE... DIR'. If --from-file or --to-file is given, there are no restrictions on FILES. If a FILE is `-', read standard input. |
当用我的新文件去和老文件比较那些发生了修改？
当执行比较的时候，在diff命令中使用选项 -w 能够忽略掉空格，
查看diff输出时候的注意是：
- ‘—’ 线上面的是第一个文件发生的变化
- ‘—’线向下的第二个文件发生的变化
- < 符号表示的内容，属于第一个文件，>符号表示的内容属于第二个文件
jcai@jcai-notebook:~/tmp$ cat test.txt 我们 你们现在还好吗？比较文本 jcai@jcai-notebook:~/tmp$ cat test2.txt 他们 我们 你们现在还好吗？ jcai@jcai-notebook:~/tmp$ diff test.txt test2.txt 0a1 > 他们 2c3 < 你们现在还好吗？比较文本 --- > 你们现在还好吗？ |
[命令集3.2]Linux下和磁盘相关的命令
# diskinfo -v /dev/ad2 # 显示磁盘信息(扇区/大小) (FreeBSD) # hdparm -I /dev/sda # 显示 IDE/ATA 磁盘信息 (Linux) # fdisk /dev/ad2 # 显示和修改磁盘分区表 # smartctl -a /dev/ad2 # 显示磁盘检测信息 |
[linux秘笈26]Stat命令
Stat命令被用来查看单个文件或者文件系统的状态以及属性。
显示某一个文件或者文件系统的状态
jcai@jcai-notebook:~$ stat /etc/mysql/my.cnf File: `/etc/mysql/my.cnf' Size: 3978 Blocks: 8 IO Block: 4096 regular file Device: 802h/2050d Inode: 449073 Links: 1 Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) Access: 2009-03-18 21:31:03.000000000 +0800 Modify: 2009-03-04 18:08:03.000000000 +0800 Change: 2009-03-04 18:08:03.000000000 +0800 jcai@jcai-notebook:~$ stat /home/jcai File: `/home/jcai' Size: 4096 Blocks: 8 IO Block: 4096 directory Device: fe00h/65024d Inode: 2187265 Links: 66 Access: (0755/drwxr-xr-x) Uid: ( 1000/ jcai) Gid: ( 1000/ jcai) Access: 2009-03-19 08:14:47.000000000 +0800 Modify: 2009-03-19 09:22:12.000000000 +0800 Change: 2009-03-19 09:22:12.000000000 +0800 |
使用 -f 选项来战士文件系统的状态
jcai@jcai-notebook:~$ stat -f / File: "/" ID: f346283e2da86295 Namelen: 255 Type: ext2/ext3 Block size: 4096 Fundamental block size: 4096 Blocks: Total: 4845177 Free: 3879940 Available: 3635752 Inodes: Total: 1224000 Free: 1082670 |
