今天遇到一個很奇怪的問題，在一臺linux執行df -h查看磁盤使用情況，發現卡成狗，于是著手去解決：

1、通過strace df -h追蹤是卡在什么位置

[root@new_web?~]#?strace?df?-h execve("/bin/df",?["df",?"-h"],?[/*?22?vars?*/])?=?0 brk(0)??????????????????????????????????=?0x2307000 mmap(NULL,?4096,?PROT_READ|PROT_WRITE,?MAP_PRIVATE|MAP_ANONYMOUS,?-1,?0)?=?0x7fd1715f4000 access("/etc/ld.so.preload",?R_OK)??????=?-1?ENOENT?(No?such?file?or?directory) open("/etc/ld.so.cache",?O_RDONLY)??????=?3 fstat(3,?{st_mode=S_IFREG|0644,?st_size=37353,?...})?=?0 mmap(NULL,?37353,?PROT_READ,?MAP_PRIVATE,?3,?0)?=?0x7fd1715ea000 close(3)????????????????????????????????=?0 open("/lib64/libc.so.6",?O_RDONLY)??????=?3 read(3,?"\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0p\356\1\344=\0\0\0"...,?832)?=?832 fstat(3,?{st_mode=S_IFREG|0755,?st_size=1926520,?...})?=?0 mmap(0x3de4000000,?3750152,?PROT_READ|PROT_EXEC,?MAP_PRIVATE|MAP_DENYWRITE,?3,?0)?=?0x3de4000000 mprotect(0x3de418a000,?2097152,?PROT_NONE)?=?0 mmap(0x3de438a000,?20480,?PROT_READ|PROT_WRITE,?MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE,?3,?0x18a000)?=?0x3de438a000 mmap(0x3de438f000,?18696,?PROT_READ|PROT_WRITE,?MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS,?-1,?0)?=?0x3de438f000 close(3)????????????????????????????????=?0 mmap(NULL,?4096,?PROT_READ|PROT_WRITE,?MAP_PRIVATE|MAP_ANONYMOUS,?-1,?0)?=?0x7fd1715e9000 mmap(NULL,?4096,?PROT_READ|PROT_WRITE,?MAP_PRIVATE|MAP_ANONYMOUS,?-1,?0)?=?0x7fd1715e8000 mmap(NULL,?4096,?PROT_READ|PROT_WRITE,?MAP_PRIVATE|MAP_ANONYMOUS,?-1,?0)?=?0x7fd1715e7000 arch_prctl(ARCH_SET_FS,?0x7fd1715e8700)?=?0 mprotect(0x3de438a000,?16384,?PROT_READ)?=?0 mprotect(0x3de3a1f000,?4096,?PROT_READ)?=?0 munmap(0x7fd1715ea000,?37353)???????????=?0 brk(0)??????????????????????????????????=?0x2307000 brk(0x2328000)??????????????????????????=?0x2328000 open("/usr/lib/locale/locale-archive",?O_RDONLY)?=?3 fstat(3,?{st_mode=S_IFREG|0644,?st_size=99158576,?...})?=?0 mmap(NULL,?99158576,?PROT_READ,?MAP_PRIVATE,?3,?0)?=?0x7fd16b756000 close(3)????????????????????????????????=?0 open("/etc/mtab",?O_RDONLY)?????????????=?3 fstat(3,?{st_mode=S_IFREG|0644,?st_size=366,?...})?=?0 mmap(NULL,?4096,?PROT_READ|PROT_WRITE,?MAP_PRIVATE|MAP_ANONYMOUS,?-1,?0)?=?0x7fd1715f3000 read(3,?"/dev/vda1?/?ext4?rw,barrier=0?0?"...,?4096)?=?366 read(3,?"",?4096)???????????????????????=?0 close(3)????????????????????????????????=?0 munmap(0x7fd1715f3000,?4096)????????????=?0 statfs("/",?{f_type="EXT2_SUPER_MAGIC",?f_bsize=4096,?f_blocks=10320720,?f_bfree=8614131,?f_bavail=8089869,?f_files=2621440,?f_ffree=2405901,?f_fsid={-102338008,?-1862172196},?f_namelen=255,?f_frsize=4096})?=?0 open("/usr/share/locale/locale.alias",?O_RDONLY)?=?3 fstat(3,?{st_mode=S_IFREG|0644,?st_size=2512,?...})?=?0 mmap(NULL,?4096,?PROT_READ|PROT_WRITE,?MAP_PRIVATE|MAP_ANONYMOUS,?-1,?0)?=?0x7fd1715f3000 read(3,?"#?Locale?name?alias?data?base.\n#"...,?4096)?=?2512 read(3,?"",?4096)???????????????????????=?0 close(3)????????????????????????????????=?0 munmap(0x7fd1715f3000,?4096)????????????=?0 open("/usr/share/locale/en_US.UTF-8/LC_MESSAGES/coreutils.mo",?O_RDONLY)?=?-1?ENOENT?(No?such?file?or?directory) open("/usr/share/locale/en_US.utf8/LC_MESSAGES/coreutils.mo",?O_RDONLY)?=?-1?ENOENT?(No?such?file?or?directory) open("/usr/share/locale/en_US/LC_MESSAGES/coreutils.mo",?O_RDONLY)?=?-1?ENOENT?(No?such?file?or?directory) open("/usr/share/locale/en.UTF-8/LC_MESSAGES/coreutils.mo",?O_RDONLY)?=?-1?ENOENT?(No?such?file?or?directory) open("/usr/share/locale/en.utf8/LC_MESSAGES/coreutils.mo",?O_RDONLY)?=?-1?ENOENT?(No?such?file?or?directory) open("/usr/share/locale/en/LC_MESSAGES/coreutils.mo",?O_RDONLY)?=?3 fstat(3,?{st_mode=S_IFREG|0644,?st_size=435,?...})?=?0 mmap(NULL,?435,?PROT_READ,?MAP_PRIVATE,?3,?0)?=?0x7fd1715f3000 close(3)????????????????????????????????=?0 statfs("/sys",?{f_type="SYSFS_MAGIC",?f_bsize=4096,?f_blocks=0,?f_bfree=0,?f_bavail=0,?f_files=0,?f_ffree=0,?f_fsid={0,?0},?f_namelen=255,?f_frsize=4096})?=?0 statfs("/dev/pts",?{f_type="DEVPTS_SUPER_MAGIC",?f_bsize=4096,?f_blocks=0,?f_bfree=0,?f_bavail=0,?f_files=0,?f_ffree=0,?f_fsid={0,?0},?f_namelen=255,?f_frsize=4096})?=?0 statfs("/dev/shm",?{f_type=0x1021994,?f_bsize=4096,?f_blocks=2041596,?f_bfree=2041596,?f_bavail=2041596,?f_files=2041596,?f_ffree=2041595,?f_fsid={0,?0},?f_namelen=255,?f_frsize=4096})?=?0 statfs("/proc/sys/fs/binfmt_misc",?{f_type=0x42494e4d,?f_bsize=4096,?f_blocks=0,?f_bfree=0,?f_bavail=0,?f_files=0,?f_ffree=0,?f_fsid={0,?0},?f_namelen=255,?f_frsize=4096})?=?0 statfs("/data",?{f_type="EXT2_SUPER_MAGIC",?f_bsize=4096,?f_blocks=129015406,?f_bfree=46849538,?f_bavail=40295938,?f_files=32768000,?f_ffree=32749794,?f_fsid={346710647,?-22441262},?f_namelen=255,?f_frsize=4096})?=?0###?卡在此處 statfs("/opt",?{f_type=0xff534d42,?f_bsize=0,?f_blocks=0,?f_bfree=0,?f_bavail=0,?f_files=0,?f_ffree=0,?f_fsid={0,?0},?f_namelen=4096,?f_frsize=0})?=?0 ###?卡在此處statfs("/data1",?{f_type="EXT2_SUPER_MAGIC",?f_bsize=4096,?f_blocks=129015406,?f_bfree=128955560,?f_bavail=122401960,?f_files=32768000,?f_ffree=32767852,?f_fsid={1328044912,?-550095550},?f_namelen=255,?f_frsize=4096})?=?0 statfs("/data2",?{f_type="EXT2_SUPER_MAGIC",?f_bsize=4096,?f_blocks=129015406,?f_bfree=128964770,?f_bavail=122411170,?f_files=32768000,?f_ffree=32767982,?f_fsid={-1295730252,?-1655731663},?f_namelen=255,?f_frsize=4096})?=?0 open("/usr/lib64/gconv/gconv-modules.cache",?O_RDONLY)?=?3 fstat(3,?{st_mode=S_IFREG|0644,?st_size=26060,?...})?=?0 mmap(NULL,?26060,?PROT_READ,?MAP_SHARED,?3,?0)?=?0x7fd1715ec000 close(3)????????????????????????????????=?0 fstat(1,?{st_mode=S_IFCHR|0620,?st_rdev=makedev(136,?2),?...})?=?0 mmap(NULL,?4096,?PROT_READ|PROT_WRITE,?MAP_PRIVATE|MAP_ANONYMOUS,?-1,?0)?=?0x7fd1715eb000 write(1,?"Filesystem??????Size??Used?Avail"...,?49Filesystem??????Size??Used?Avail?Use%?Mounted?on )?=?49 write(1,?"/dev/vda1????????40G??6.6G???31G"...,?40/dev/vda1????????40G??6.6G???31G??18%?/ )?=?40 write(1,?"tmpfs???????????7.8G?????0??7.8G"...,?47tmpfs???????????7.8G?????0??7.8G???0%?/dev/shm )?=?47 write(1,?"/dev/vdb????????493G??314G??154G"...,?44/dev/vdb????????493G??314G??154G??68%?/data )?=?44 write(1,?"/dev/vdc????????493G??234M??467G"...,?45/dev/vdc????????493G??234M??467G???1%?/data1 )?=?45 write(1,?"/dev/vdd????????493G??198M??467G"...,?45/dev/vdd????????493G??198M??467G???1%?/data2 )?=?45 close(1)????????????????????????????????=?0 munmap(0x7fd1715eb000,?4096)????????????=?0 close(2)????????????????????????????????=?0 exit_group(0)???????????????????????????=??

觀察的時候發現追蹤到/opt的時候卡住了

但是df -h的結果來看，確實沒有/opt的掛載信息，于是進入/opt，發現也是奇卡無比

于是使用 mount |column -t 查看所有的掛載信息

[root@new_web?/]#?mount?|?column?-t /dev/vda1??????????????????on??/?????????????????????????type??ext4?????????(rw,barrier=0) proc???????????????????????on??/proc?????????????????????type??proc?????????(rw) sysfs??????????????????????on??/sys??????????????????????type??sysfs????????(rw) devpts?????????????????????on??/dev/pts??????????????????type??devpts???????(rw,gid=5,mode=620) tmpfs??????????????????????on??/dev/shm??????????????????type??tmpfs????????(rw) none???????????????????????on??/proc/sys/fs/binfmt_misc??type??binfmt_misc??(rw) /dev/vdb???????????????????on??/data?????????????????????type??ext4?????????(rw) //192.168.2.6/replication??on??/opt??????????????????????type??cifs?????????(rw,username=dba,password=0987654) /dev/vdc???????????????????on??/data1????????????????????type??ext4?????????(rw) /dev/vdd???????????????????on??/data2????????????????????type??ext4?????????(rw)

發現/opt掛載了遠程nfs系統，卸載/opt

umount?/opt

再次執行df -h 發現秒開！！

問題原因：

此處的NFS系統已經不使用了（掛了），但是它的掛載信息還在，導致文件系統一直在查找，所以就一直卡在那里

????

轉載于:https://blog.51cto.com/chenyicai/1924649

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