[命令集3.6]挂载/重挂载一个文件系统
举个 cdrom 的例子。如果已经列于 /etc/fstab 中:
# mount /cdrom
或在 /dev/ 中查找设备,亦或使用 dmesg 命令
FreeBSD
# mount -v -t cd9660 /dev/cd0c /mnt # cdrom # mount_cd9660 /dev/wcd0c /cdrom # 另外一个方法 # mount -v -t msdos /dev/fd0c /mnt # 软驱
/etc/fstab 中的一条:
# Device Mountpoint FStype Options Dump Pass# /dev/acd0 /cdrom cd9660 ro,noauto 0 0
要允许用户做这些,可以这么做:
# sysctl vfs.usermount=1 # 或者在 /etc/sysctl.conf 中插入一条 "vfs.usermount=1"
Linux
# mount -t auto /dev/cdrom /mnt/cdrom # 典型的 cdrom 挂载命令 # mount /dev/hdc -t iso9660 -r /cdrom # IDE # mount /dev/sdc0 -t iso9660 -r /cdrom # SCSI
/etc/fstab 中的条目:
/dev/cdrom /media/cdrom subfs noauto,fs=cdfss,ro,procuid,nosuid,nodev,exec 0 0
用 Linux 挂载一个 FreeBSD 分区
用 fdisk 查找分区号,这通常是 root 分区,但也可能是其他 BSD slice。如果 FreeBSD 有许多 slice,他们
不列于同一个 fdisk 分区表中,但可见于 /dev/sda* 或 /dev/hda* 中。
# fdisk /dev/sda # 查找 FreeBSD 分区 /dev/sda3 * 5357 7905 20474842+ a5 FreeBSD # mount -t ufs -o ufstype=ufs2,ro /dev/sda3 /mnt /dev/sda10 = /tmp; /dev/sda11 /usr # 其他 slice
重挂载
不用卸载一个设备来重挂载。 对 fsck 来说是必须的。举个例子:
# mount -o remount,ro / # Linux # mount -o ro / # FreeBSD
从 cdrom 拷贝原始数据进一个 iso 映像文件:
# dd if=/dev/cd0c of=file.isoTags: command, Hack, Linux
[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.
[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？ |
[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 |
[命令集3.1]linux文件的权限
用 chmod 和 chown 更改访问权限和所有权。对于所有用户的默认掩码(umask)可以在 /etc/profile (Linux)
或 /etc/login.conf (FreeBSD) 中修改。其默认掩码(umask)通常为 022。掩码可以和777做减法,从而得到755
的权限。
1 –x 执行 # Mode 764 = 执行/读/写 | 读/写 | 读
2 -w- 写 # |—所有者|—用户组|—其他用户|
4 r– 读
ugo=a u=所有者, g=用户组, o=其他用户, a=所有用户
# chmod [OPTION] MODE[,MODE] FILE # MODE 可以是 [ugoa]*([-+=]([rwxXst])) # chmod 640 /var/log/maillog # 更改 maillog 访问权限为 -rw-r----- # chmod u=rw,g=r,o= /var/log/maillog # 同上 # chmod -R o-r /home/* # 递归去除所有其他用户的可读权限 在可执行位设置 SUID (知道你在干什么!13) # chmod u+s /path/to/prog # # find / -perm -u+s -print # 查找所有设置过 SUID 位的程序 # chown user:group /path/to/file # 改变文件的所有者和文件关联的组 # chgrp group /path/to/file # 改变文件关联的组 # chmod 640 `find ./ -type f -print` # Change permissions to 640 for all files # chmod 751 `find ./ -type d -print` # Change permissions to 751 for all directories |
Linux秘笈25.Linux的Cut命令
Cut command can be used to display only specific columns from a text file or
other command outputs.
Following are some of the examples.
Display the 1st field (employee name) from a colon delimited file
$ cut -d: -f 1 names.txt Emma Thomas Alex Jason Madison Randy Sanjay Gupta Nisha Singh |
Display 1st and 3rd field from a colon delimited file
$ cut -d: -f 1,3 names.txt Emma Thomas:Marketing Alex Jason:Sales Madison Randy:Product Development Sanjay Gupta:Support Nisha Singh:Sales |
Display only the first 8 characters of every line in a file
$ cut -c 1-8 names.txt Emma Tho Alex Jas Madison Sanjay G Nisha Si |
[命令集]对前后台的进程进行调出和调入
前台/后台
当一个进程在shell 中已运行，可以使用[Ctrl]-[Z] (^Z), bg 和fg 来调入调出前后台10。举个例子：启动
2 个进程，调入后台。使用jobs 列出后台列表，然后再调入一个进程到前台。
# ping cb.vu > ping.log ^Z # ping 使用 [Ctrl]-[Z] 来暂停(停止) # bg # 调入后台继续运行 # jobs -l # 后台进程列表 [1] - 36232 Running ping cb.vu > ping.log [2] + 36233 Suspended (tty output) top # fg %2 # 让进程 2 返回到前台运行 |
使用nohup 开启一个持续运行的进程直到 shell 被关闭(避免挂断)。
# nohup ping -i 60 > ping.log &
