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Linux調試工具lsof的深入分析

Posted on 2012-03-26 09:06 S.l.e!ep.￠% 閱讀(2492) 評論(0) 編輯收藏引用所屬分類: gdb

1)查看對某個文件的使用情況
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root@troy:/# lsof -w /etc/passwd
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COMMAND? PID USER?? FD?? TYPE DEVICE SIZE/OFF??? NODE NAME
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python? 2340 troy?? 10r?? REG??? 8,1???? 1804 2886346 /etc/passwd
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-------------------------------------------------------
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注:-w參數表示不打印警告信息.
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lsof程序會打開/proc/PID/fd/目錄找到對映的文件句柄,再通過stat系統調用得到文件的詳細信息.
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同時還會利用fdinfo目錄下的文件句柄得到打開文件時的狀態.
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例如:
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1.1)創建程序test.c,本程序在/tmp/目錄下以O_WRONLY(只寫)和O_SYNC(同步)方式打開temp文件.
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root@troy:/tmp# more test.c
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#include <unistd.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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int main ()
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{
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??????? int fd;
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??????? fd = open("/tmp/temp", O_WRONLY|O_SYNC);
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??????? lseek(fd, 80L, SEEK_SET);
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??????? sleep(100);
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??????? close(fd);
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??????? return 0;
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}
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root@troy:/tmp# gcc test.c -o testfd
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root@troy:/tmp# ./testfd &
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1.2)觀察testfd程序打開的文件/tmp/temp
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cat /proc/$(lsof -w /tmp/temp|awk '/testfd/{print $2}')/fdinfo/3
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pos: 80
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flags: 0110001
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-------------------------------------------------------
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我們看到程序輸出pos和flags兩組數據,pos字段表示被打開文件的當前讀寫位置,flags表示以文件方式打開該文件.
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pos為80表示從文件起始位置移動80個字節的位置.
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flags為0110001中的xxxxxx1表示以只寫方式打開文件,如果是只讀則為xxxxxx0,如果可讀可寫則為xxxxxx2,
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其中的xx1xxxx表示以同步方式(O_SYNC)打開文件,如果改用以O_ASYNC方式打開文件,則為xx2xxxx,
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如果同時指定了O_SYNC和O_ASYNC兩種方式打開文件,結果則為xx3xxxx.
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如果我們增加了O_APPEND方式打開文件,結果則為xxx2xxx.
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如果我們增加了O_NONBLOCK方式打開文件,結果則為xxx4xxx.
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如果同時指定了O_APPEND和NONBLOCK兩種方式,結果則為xxx6xxx.
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最后指明一下O_ASYNC用于打開終端和socket文件,默認產生SIGIO信號.
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而O_NONBLOCK表示不阻塞打開的文件,只用于FIFO的管道文件中.
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2)查看對某個目錄的使用情況
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我們先執行上個試驗的程序.
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-------------------------------------------------------
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root@troy:~# /tmp/testfd &
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[1] 17021
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root@troy:~# lsof +d /tmp/
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COMMAND?? PID USER?? FD?? TYPE???????????? DEVICE SIZE/OFF?? NODE NAME
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gedit??? 2531 troy??? 7u? unix 0xffff880029a49b00????? 0t0? 17106 /tmp/gedit.troy.917415843
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testfd? 17021 root? txt??? REG??????????????? 8,1???? 8617 262475 /tmp/testfd
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testfd? 17021 root??? 3w?? REG??????????????? 8,1??????? 0 262412 /tmp/temp
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bash??? 3926? troy? cwd??? DIR??????????????? 8,1???? 4096 262149 /tmp
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bash??? 4001? troy? cwd??? DIR??????????????? 8,1???? 4096 262149 /tmp
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-------------------------------------------------------
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如果不加參數+d呢?這里我們只看到了用戶的當前使用目錄,如下:
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root@troy:~# lsof -w /tmp
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COMMAND? PID USER?? FD?? TYPE DEVICE SIZE/OFF?? NODE NAME
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bash??? 3926 troy? cwd??? DIR??? 8,1???? 4096 262149 /tmp
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bash??? 4001 troy? cwd??? DIR??? 8,1???? 4096 262149 /tmp
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-------------------------------------------------------
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有什么區別嗎？
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加+d參數的情況下,lsof會遍列所有的進程,以及進程下所有的fd,fdinfo,cwd,root,exec,maps,以查找被程序占用中的目錄.
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而不加參數+d的情況下,lsof只會遍列所有進程的cwd,cwd是用戶當前目錄的軟鏈接.如下:
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root@troy:~# ls -l /proc/3926/cwd
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lrwxrwxrwx 1 troy troy 0 2011-02-09 19:23 /proc/3926/cwd -> /tmp
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-------------------------------------------------------
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3)查看某個進程的使用情況
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-------------------------------------------------------
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troy@troy:/proc/23294$ lsof -p 23294
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COMMAND?? PID USER?? FD?? TYPE? DEVICE SIZE/OFF??? NODE NAME
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ssh???? 23294 troy? cwd??? DIR???? 8,1???? 4096? 262149 /tmp
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ssh???? 23294 troy? rtd??? DIR???? 8,1???? 4096?????? 2 /
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ssh???? 23294 troy? txt??? REG???? 8,1?? 339712 1058082 /usr/bin/ssh
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ssh???? 23294 troy? mem??? REG???? 8,1??? 51712? 787472 /lib/libnss_files-2.11.1.so
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ssh???? 23294 troy? mem??? REG???? 8,1??? 43552? 787456 /lib/libnss_nis-2.11.1.so
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ssh???? 23294 troy? mem??? REG???? 8,1??? 97256? 787430 /lib/libnsl-2.11.1.so
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ssh???? 23294 troy? mem??? REG???? 8,1??? 35712? 787454 /lib/libnss_compat-2.11.1.so
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ssh???? 23294 troy? mem??? REG???? 8,1?? 135745? 787466 /lib/libpthread-2.11.1.so
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ssh???? 23294 troy? mem??? REG???? 8,1??? 10224? 787804 /lib/libkeyutils-1.2.so
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ssh???? 23294 troy? mem??? REG???? 8,1??? 31168 1050775 /usr/lib/libkrb5support.so.0.1
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ssh???? 23294 troy? mem??? REG???? 8,1??? 14584? 798518 /lib/libcom_err.so.2.1
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ssh???? 23294 troy? mem??? REG???? 8,1?? 154048 1050756 /usr/lib/libk5crypto.so.3.1
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ssh???? 23294 troy? mem??? REG???? 8,1?? 803192 1050769 /usr/lib/libkrb5.so.3.3
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ssh???? 23294 troy? mem??? REG???? 8,1??? 14696? 795838 /lib/libdl-2.11.1.so
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ssh???? 23294 troy? mem??? REG???? 8,1? 1572232? 787469 /lib/libc-2.11.1.so
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ssh???? 23294 troy? mem??? REG???? 8,1?? 213784 1050761 /usr/lib/libgssapi_krb5.so.2.2
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ssh???? 23294 troy? mem??? REG???? 8,1??? 93000? 787444 /lib/libresolv-2.11.1.so
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ssh???? 23294 troy? mem??? REG???? 8,1??? 92752? 786985 /lib/libz.so.1.2.3.3
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ssh???? 23294 troy? mem??? REG???? 8,1? 1622304? 796093 /lib/libcrypto.so.0.9.8
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ssh???? 23294 troy? mem??? REG???? 8,1?? 136936? 787431 /lib/ld-2.11.1.so
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ssh???? 23294 troy??? 0u?? CHR? 136,20????? 0t0????? 23 /dev/pts/20
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ssh???? 23294 troy??? 1u?? CHR? 136,20????? 0t0????? 23 /dev/pts/20
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ssh???? 23294 troy??? 2u?? CHR? 136,20????? 0t0????? 23 /dev/pts/20
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ssh???? 23294 troy??? 3u? IPv4 1603924????? 0t0???? TCP troy.local:41879->10.1.1.7:ssh (ESTABLISHED)
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ssh???? 23294 troy??? 4w? FIFO???? 0,8????? 0t0 1603904 pipe
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ssh???? 23294 troy??? 5u?? CHR? 136,19????? 0t0????? 22 /dev/pts/19
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ssh???? 23294 troy??? 6r?? CHR???? 5,0????? 0t0??? 1129 /dev/tty
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ssh???? 23294 troy??? 7u?? CHR? 136,21????? 0t0????? 24 /dev/pts/21
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ssh???? 23294 troy??? 8u?? CHR? 136,20????? 0t0????? 23 /dev/pts/20
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ssh???? 23294 troy??? 9u?? CHR? 136,20????? 0t0????? 23 /dev/pts/20
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ssh???? 23294 troy?? 10u?? CHR? 136,20????? 0t0????? 23 /dev/pts/20
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-------------------------------------------------------
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lsof程序會跟據用戶指定的PID，遍列/proc/目錄找到該PID，在/proc/PID目錄下依次打開stat,maps,fd,fdinfo.
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stat文件包含了當前進程的信息.
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當前進程的stat如下:
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23294 (ssh) S 23291 23294 23294 34837 23294 4202496 836 0 0 0 8 10 0 0 20 0 1 0 29282141 39632896 658 18446744073709551615 140114439372800 140114439700540 140733214155456 140733214149016 140114423930835 0 0 4096 136331271 18446744071580239593 0 0 17 1 0 0 0 0 0
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maps文件包含映像的文件:
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當前進程的maps如下:
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7f6eecf42000-7f6eecf4e000 r-xp 00000000 08:01 787472???????????????????? /lib/libnss_files-2.11.1.so
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7f6eecf4e000-7f6eed14d000 ---p 0000c000 08:01 787472???????????????????? /lib/libnss_files-2.11.1.so
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7f6eed14d000-7f6eed14e000 r--p 0000b000 08:01 787472???????????????????? /lib/libnss_files-2.11.1.so
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7f6eed14e000-7f6eed14f000 rw-p 0000c000 08:01 787472???????????????????? /lib/libnss_files-2.11.1.so
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7f6eed14f000-7f6eed159000 r-xp 00000000 08:01 787456???????????????????? /lib/libnss_nis-2.11.1.so
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7f6eed159000-7f6eed358000 ---p 0000a000 08:01 787456???????????????????? /lib/libnss_nis-2.11.1.so
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7f6eed358000-7f6eed359000 r--p 00009000 08:01 787456???????????????????? /lib/libnss_nis-2.11.1.so
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7f6eed359000-7f6eed35a000 rw-p 0000a000 08:01 787456???????????????????? /lib/libnss_nis-2.11.1.so
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7f6eed35a000-7f6eed371000 r-xp 00000000 08:01 787430???????????????????? /lib/libnsl-2.11.1.so
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7f6eed371000-7f6eed570000 ---p 00017000 08:01 787430???????????????????? /lib/libnsl-2.11.1.so
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7f6eed570000-7f6eed571000 r--p 00016000 08:01 787430???????????????????? /lib/libnsl-2.11.1.so
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7f6eed571000-7f6eed572000 rw-p 00017000 08:01 787430???????????????????? /lib/libnsl-2.11.1.so
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后省略.
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這里用pmap 23294也可以找到加載的文件與虛擬地址的對映.
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fd,fdinfo我們已經分析過了,當lsof找到/proc/23294/3時,發現是個socket文件,如下:
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----------------------------------------------------
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troy@troy:/proc/23294/fd$ ls -l
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total 0
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lrwx------ 1 troy troy 64 2011-02-11 02:47 0 -> /dev/pts/20
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lrwx------ 1 troy troy 64 2011-02-11 02:47 1 -> /dev/pts/20
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lrwx------ 1 troy troy 64 2011-02-11 02:47 10 -> /dev/pts/20
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lrwx------ 1 troy troy 64 2011-02-11 01:07 2 -> /dev/pts/20
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lrwx------ 1 troy troy 64 2011-02-11 02:47 3 -> socket:[1603924]
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l-wx------ 1 troy troy 64 2011-02-11 02:47 4 -> pipe:[1603904]
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lrwx------ 1 troy troy 64 2011-02-11 02:47 5 -> /dev/pts/19
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lr-x------ 1 troy troy 64 2011-02-11 02:47 6 -> /dev/tty
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lrwx------ 1 troy troy 64 2011-02-11 02:47 7 -> /dev/pts/21
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lrwx------ 1 troy troy 64 2011-02-11 02:47 8 -> /dev/pts/20
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lrwx------ 1 troy troy 64 2011-02-11 02:47 9 -> /dev/pts/20
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----------------------------------------------------
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此時會依次打開以下的文件,對網絡套字接進行分析,各文件作用如下:
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/proc/net/raw ---->原始套接字
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/proc/net/unix ---->UNIX套接字
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/proc/net/sockstat ---->當前套接字的使用情況
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/proc/net/tcp ---->TCP套接字
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/proc/net/udp ---->UDP套接字
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/proc/net/udplite --->UDP無線通訊套接字
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在/proc/net/tcp會找到對映的inode,socket:[1603924]的inode為1603924,而tcp中sl為12的一行正是這個socket服務.如下:
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----------------------------------------------------
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more /proc/net/tcp
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? sl? local_address rem_address?? st tx_queue rx_queue tr tm->when retrnsmt?? uid? timeout inode???????????????????????????????????????????????????
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?? 0: 00000000:0087 00000000:0000 0A 00000000:00000000 00:00000000 00000000???? 0??????? 0 8984 1 ffff8800677d1380 300 0 0 2 -1????????????????????
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?? 1: 00000000:0369 00000000:0000 0A 00000000:00000000 00:00000000 00000000???? 0??????? 0 8575 1 ffff8800677d0d00 300 0 0 2 -1????????????????????
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?? 2: 00000000:0050 00000000:0000 0A 00000000:00000000 00:00000000 00000000???? 0??????? 0 8673 1 ffff880068c51a00 300 0 0 2 -1????????????????????
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?? 3: 00000000:1770 00000000:0000 0A 00000000:00000000 00:00000000 00000000???? 0??????? 0 5350 1 ffff880068c50680 300 0 0 2 -1????????????????????
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?? 4: 00000000:0016 00000000:0000 0A 00000000:00000000 00:00000000 00000000???? 0??????? 0 4315 1 ffff880068c50000 300 0 0 2 -1????????????????????
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?? 5: 0100007F:0277 00000000:0000 0A 00000000:00000000 00:00000000 00000000???? 0??????? 0 25571 1 ffff88001a06c780 300 0 0 2 -1???????????????????
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?? 6: 00000000:0BB8 00000000:0000 0A 00000000:00000000 00:00000000 00000000???? 0??????? 0 7881 1 ffff8800677d0680 300 0 0 2 -1????????????????????
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?? 7: 00000000:BD59 00000000:0000 0A 00000000:00000000 00:00000000 00000000???? 0??????? 0 8986 1 ffff880068c52080 300 0 0 2 -1????????????????????
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?? 8: 0100007F:0019 00000000:0000 0A 00000000:00000000 00:00000000 00000000???? 0??????? 0 6304 1 ffff880068c50d00 300 0 0 2 -1????????????????????
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?? 9: 4506010A:D6E9 0701010A:0016 01 00000000:00000000 02:00028405 00000000? 1502??????? 0 1603452 2 ffff880057896180 22 4 8 5 -1??????????????????
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? 10: 4506010A:89A5 0701010A:0016 01 00000000:00000000 02:00091EFF 00000000? 1502??????? 0 1672803 2 ffff88001a068680 25 4 18 4 -1??????????????????
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? 11: 4506010A:872E 0701010A:0016 01 00000000:00000000 02:0004B77C 00000000? 1502??????? 0 1177942 2 ffff880057893a80 125 4 0 3 2??????????????????
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? 12: 4506010A:A397 0701010A:0016 01 00000000:00000000 02:0004D6A6 00000000? 1502??????? 0 1603924 2 ffff880057894e00 23 4 0 5 -1??????????????????
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? 13: 4506010A:BD31 0701010A:0016 01 00000000:00000000 02:000139A5 00000000? 1502??????? 0 1345002 2 ffff880057897500 22 4 0 5 -1??????????????????
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? 14: 4506010A:8F21 0701010A:0016 01 00000000:00000000 02:000192BE 00000000? 1502??????? 0 1351794 2 ffff880057896800 25 4 12 4 -1?????????????????
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? 15: 4506010A:8AD1 0701010A:0016 01 00000000:00000000 02:00094915 00000000? 1502??????? 0 1447912 2 ffff880068c55b00 21 4 14 4 -1
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----------------------------------------------------
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其中local_address代表本地的IP和端口
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4506010A(本地地址)的45轉化為十進制是69,06轉化為十制制是6,01轉化為十進制是1,0A轉化為十進制是10,倒過來也就是10.1.1.69,是本地地址.
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A397(本地端口)轉化為十進制是41879,也就是本地端口
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rem_address代表遠程IP和端口
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0701010A(遠程地址):10.1.1.7
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0016(遠程端口)22
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其它參數都是內核調試時使用
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uid就是用戶的UID
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4)顯示所屬user進程打開的文件
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----------------------------------------------------
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root@troy:/proc/2554# lsof -u test -w
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COMMAND? PID USER?? FD?? TYPE???????????? DEVICE SIZE/OFF??? NODE NAME
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su????? 2554 test? cwd??? DIR??????????????? 8,1???? 4096?????? 2 /
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su????? 2554 test? rtd??? DIR??????????????? 8,1???? 4096?????? 2 /
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su????? 2554 test? txt??? REG??????????????? 8,1??? 36864? 262185 /bin/su
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su????? 2554 test? mem??? REG??????????????? 8,1??? 27024? 797476 /lib/libnss_lsass.so.2.0.0
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su????? 2554 test? mem??? REG??????????????? 8,1??? 10272 1102794 /usr/lib/gconv/IBM850.so
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su????? 2554 test? mem??? REG??????????????? 8,1??? 14392 1102782 /usr/lib/gconv/UTF-16.so
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su????? 2554 test? mem??? REG??????????????? 8,1??? 43528? 795516 /lib/security/pam_gnome_keyring.so
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su????? 2554 test? mem??? REG??????????????? 8,1?? 256768? 787477 /lib/libdbus-1.so.3.4.0
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su????? 2554 test? mem??? REG??????????????? 8,1??? 14536 1052877 /usr/lib/libck-connector.so.0.0.0
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su????? 2554 test? mem??? REG??????????????? 8,1??? 10360? 795488 /lib/security/pam_ck_connector.so
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su????? 2554 test? mem??? REG??????????????? 8,1??? 14344? 787928 /lib/libgpg-error.so.0.4.0
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su????? 2554 test? mem??? REG??????????????? 8,1?? 491000? 787918 /lib/libgcrypt.so.11.5.2
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su????? 2554 test? mem??? REG??????????????? 8,1??? 92752? 786985 /lib/libz.so.1.2.3.3
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su????? 2554 test? mem??? REG??????????????? 8,1??? 67896 1055840 /usr/lib/libtasn1.so.3.1.7
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su????? 2554 test? mem??? REG??????????????? 8,1??? 10224? 787804 /lib/libkeyutils-1.2.so
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su????? 2554 test? mem??? REG??????????????? 8,1??? 31168 1050775 /usr/lib/libkrb5support.so.0.1
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su????? 2554 test? mem??? REG??????????????? 8,1??? 14584? 798518 /lib/libcom_err.so.2.1
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以下略
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----------------------------------------------------
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通過strace,我們知道lsof通過stat系統調用得到這個進程的目錄owner,正是我們要找的用戶進程.
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如下:
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stat("/proc/2554/", {st_mode=S_IFDIR|0555, st_size=0, ...}) = 0
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open("/proc/2554/stat", O_RDONLY)?????? = 4
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read(4, "2554 (su) S 2533 2554 2533 34817"..., 4096) = 241
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最后lsof通過調用cwd,root,fd,fdinfo,maps以及網絡套接字顯示輸出用戶進程所使用的文件.
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5)顯示網絡服務
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----------------------------------------------------
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root@troy:~# lsof -i
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COMMAND??? PID??????? USER?? FD?? TYPE DEVICE SIZE/OFF NODE NAME
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smbd?????? 767??????? root?? 22u? IPv6?? 4410????? 0t0? TCP *:microsoft-ds (LISTEN)
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smbd?????? 767??????? root?? 23u? IPv6?? 4412????? 0t0? TCP *:netbios-ssn (LISTEN)
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sshd?????? 787??????? root??? 3u? IPv4?? 4227????? 0t0? TCP *:ssh (LISTEN)
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sshd?????? 787??????? root??? 4u? IPv6?? 4229????? 0t0? TCP *:ssh (LISTEN)
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avahi-dae? 809?????? avahi?? 13u? IPv4?? 4568????? 0t0? UDP *:mdns
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avahi-dae? 809?????? avahi?? 14u? IPv4?? 4569????? 0t0? UDP *:50511
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dhclient?? 883??????? root??? 5u? IPv4?? 4530????? 0t0? UDP *:bootpc
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Xorg?????? 912??????? root??? 1u? IPv6?? 4705????? 0t0? TCP *:x11 (LISTEN)
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Xorg?????? 912??????? root??? 3u? IPv4?? 4706????? 0t0? TCP *:x11 (LISTEN)
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dcerpcd?? 1132??????? root?? 15u? IPv4?? 8845????? 0t0? TCP *:loc-srv (LISTEN)
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dcerpcd?? 1132??????? root?? 16u? IPv4?? 8846????? 0t0? UDP *:loc-srv
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eventlogd 1261??????? root?? 14u? IPv4?? 8850????? 0t0? TCP *:55846 (LISTEN)
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exim4???? 1563 Debian-exim??? 3u? IPv4?? 6359????? 0t0? TCP localhost:smtp (LISTEN)
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以下略
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----------------------------------------------------
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lsof通過遍列所有進程的所有文件句柄,找到網絡套接字,再通過/proc/net/下面的網絡信息得到具體的套接字信息.

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