如何自动查找和报告断开的符号链接？

作为整洁的系统管理员，我们希望确保（在时间允许的情况下）小事情与大问题一样被覆盖。其中之一是确保我们的系统不充满破碎的符号链接。

为什么这些小坏蛋有问题？因为它们使您认为文件不在时就在那儿，所以它们可能表示更烦人，并且因为运行某些命令（例如grep -r）时，我的（小巧）OCD部分变得疯狂，并且受到所有这些警告的困扰。

因此，如何去检测（并通过电子邮件或监视系统报告）管理员负责的系统各部分中的断开链接（毫无意义的告诉我，~jbloggs有很多断开的符号链接，这就是他的问题） ）？

问题-L在于副作用是将搜索扩展到symlinks可能是预期或不期望的目标的子目录中。

随着GNU findutils版本find：

<!-- language: bash -->
find /path/to/search -xtype l

除了找不到循环的符号链接。

-execdir 在另一个答案中，它不是那么可移植的，因此将其提炼为可移植的解决方案，该解决方案可以找到损坏的符号链接，包括循环链接：

<!-- language: bash -->
find /path/to/search -type l -exec test ! -e {} \; -print

请参阅此问题或ynform.org进行进一步的讨论。另请参阅findutils文档以获取详细信息。ynform.org链接还提出了一种仅检测循环链接的方法。

剥猫的很多方法

这是非常便携式的（-L是posix要求）

find -L /path/you/care/about -type l 2>/dev/null | mail -s "Broken symlinks detected" womble@example.com

您没有定义损坏的链接，以上内容会向您发送损坏的链接，这些链接在您关心的文件系统部分中没有目标。它还报告有关stderr文件系统循环和太多级别的符号链接等问题的信息。如果您也关心它们，则将stderr重定向到您的邮件

find -L /path/you/care/about -type l 2>&1 | mail ...

如果您找到支持的话，它既-readable有用又快速

find /path/you/care/about -type l ! -readable | mail ...

上面的链接在输出中包含太多级别的符号链接问题，但没有文件系统循环。

如果您关心的文件系统部分具有不同的路径，则

find /path/you/care/about /another/path ...

我将给您一个Linux答案，如果需要，您可以将其调整为Unix：

find . -type l ! -execdir test -e {} \; -print >> broken_symlinks.txt; mutt -s "Broken symlinks" womble@example.com < broken_symlinks.txt; rm -f broken_symlinks.txt

第二个选项是ls -LR | grep 'cannot access'上面的find命令或对它们的一些修改。

编辑：

是的，这甚至更好： find . -type l ! -execdir test -e {} \; -print | mail -s "Broken symlinks" womble@example.com

这是使用GNU find实现的一种好方法：

find <root_dir_of_find> -follow -lname '*' | mail sysadmin -s 'Broken symlink report'

之所以起作用，是因为根据查找手册页，-lname使用-follow（或-L）“ ...除非符号链接断开，否则此测试将返回false”。

当服务器使用率不高时，运行这种磁盘扫描可能是明智的。使用nice和/或ionice（请参阅此博客以获取有关ionice的详细说明）可能会很有用，以减少运行此任务时服务器上的负载。

Fedora和Ubuntu提供了该symlinks实用程序。该实用程序是本机elf可执行文件，而不是包装外壳程序脚本。该实用程序已预先安装在Fedora上。您可能需要在Ubuntu上安装该实用程序。

使用该symlinks实用程序，您可以使用以下命令审核悬空链接。

sudo symlinks -r /usr | grep dangling

如果悬空链接的目标可以删除，则发出以下命令将其删除。

sudo symlinks -r -d /usr

这是Fedora 31服务器上的输出示例。该debian-logo.png和ubuntu-logo.png是正确的。

$ sudo symlinks -r /usr | grep dangling
dangling: /usr/lib/.build-id/0a/21c737b7a56e803b12724b2bc4a8d27654ee0e -> ../../../../usr/lib64/perl5/auto/Cwd/Cwd.so
dangling: /usr/lib/.build-id/0c/352d0ca7513dad8eb098d3ad0684379a835aed -> ../../../../usr/lib64/perl5/auto/Unicode/Collate/Collate.so
dangling: /usr/lib/.build-id/1b/99d9d65010cdcc2193b873e7e825e70e23422b -> ../../../../usr/sbin/quota_nld
dangling: /usr/lib/.build-id/1c/c667de4368e4d621257070a451684c373f9952 -> ../../../../usr/sbin/rpc.rquotad
dangling: /usr/lib/.build-id/24/cfecf40f5fca30662589eb016da08a28767697 -> ../../../../usr/lib64/perl5/auto/DB_File/DB_File.so
dangling: /usr/lib/.build-id/25/42192b89d9eaf9c9782b0c22f91ee6440482cd -> ../../../../usr/lib64/dovecot/lib95_imap_filter_sieve_plugin.so
dangling: /usr/lib/.build-id/2a/a949ebff931bc3732fc396a0f2b294bb9e854b -> ../../../../usr/lib64/perl5/auto/Digest/MD5/MD5.so
dangling: /usr/lib/.build-id/34/2a46c23513258e09e87d6808b784a8b6491ff8 -> ../../../../usr/lib64/perl5/auto/Storable/Storable.so
dangling: /usr/lib/.build-id/43/e0a6db8e2b4f4aeb8f5ebb69f3cc716fc5d1cd -> ../../../../usr/lib64/perl5/auto/threads/shared/shared.so
dangling: /usr/lib/.build-id/4a/661475701d2cdcfb7d085c3e6f9bd05485d207 -> ../../../../usr/bin/coreutils.single
dangling: /usr/lib/.build-id/65/46b22b19cdfee2dfab7754d8d7ea316342151b -> ../../../../usr/lib64/perl5/auto/Compress/Raw/Zlib/Zlib.so
dangling: /usr/lib/.build-id/73/60dbe43c8b6c4a666a3bd0dc75e16a679bb784 -> ../../../../usr/lib64/libncurses++.so.6.1
dangling: /usr/lib/.build-id/7a/26a4df12398dbb4130f04a1c367a4dcc7d442b -> ../../../../usr/lib64/perl5/auto/Unicode/Normalize/Normalize.so
dangling: /usr/lib/.build-id/7f/fd3bbd111b6654bfd1b243704efa96ec2d4863 -> ../../../../usr/lib64/perl5/auto/Encode/EBCDIC/EBCDIC.so
dangling: /usr/lib/.build-id/83/2c8a2df088752fdcc9a9551ffce7b3176a4d49 -> ../../../../usr/lib64/perl5/auto/Compress/Raw/Bzip2/Bzip2.so
dangling: /usr/lib/.build-id/8b/65c6430553b93525c53d5cc2ba8fcf4ff3aaee -> ../../../../usr/lib64/perl5/auto/MIME/Base64/Base64.so
dangling: /usr/lib/.build-id/8d/c5a840771ecedd3469ee2f46d069a2eda43bf4 -> ../../../../usr/lib64/perl5/auto/Sys/Syslog/Syslog.so
dangling: /usr/lib/.build-id/91/5242c5632706f91d83e37781b0f9f3fea7095e -> ../../../../usr/lib64/perl5/auto/Encode/JP/JP.so
dangling: /usr/lib/.build-id/ce/88cf936cb7a769cb86fc5a6573e9eb1dd34f11 -> ../../../../usr/sbin/warnquota
dangling: /usr/lib/.build-id/cf/4163f54ccf50ecdf167458d9c191340923e397 -> ../../../../usr/lib64/dovecot/lib90_sieve_plugin.so
dangling: /usr/lib/.build-id/db/462bcd4628914e304d29efdb91c9ef4c8a429c -> ../../../../usr/libexec/dovecot/managesieve
dangling: /usr/lib/.build-id/e4/d5521acb2c6258e041ce769b598b2321b1b759 -> ../../../../usr/lib64/perl5/auto/threads/threads.so
dangling: /usr/lib/.build-id/e8/90366944201ec9b95741c6412384694bdd7512 -> ../../../../usr/lib64/perl5/auto/Data/Dumper/Dumper.so
dangling: /usr/lib/.build-id/e8/249d9630ae331b9202bae7f673e9252fa7253b -> ../../../../usr/sbin/xfs_scrub
dangling: /usr/lib/.build-id/e9/84aa80676f59c7c2509cbff7adc9c75eda481f -> ../../../../usr/lib64/perl5/auto/Encode/TW/TW.so
dangling: /usr/lib/.build-id/eb/adfc3dbd92dd3c040503abd748801b545cc86f -> ../../../../usr/lib64/perl5/auto/Time/Piece/Piece.so
dangling: /usr/lib/.build-id/f1/9dc36368503cdc9fefccc69d5746b63e47908d -> ../../../../usr/libexec/dovecot/managesieve-login
dangling: /usr/lib/.build-id/f4/39e5769bde9d9f8d4544c8f71196ad71ac5f51 -> ../../../../usr/lib64/perl5/auto/Encode/Symbol/Symbol.so
dangling: /usr/lib/.build-id/f5/78cbcea9f6912e60cdddb66910261996ad6141 -> ../../../../usr/lib64/perl5/auto/Encode/Byte/Byte.so
dangling: /usr/lib/.build-id/fc/6f59624f604d702f001f613defb4e076937073 -> ../../../../usr/lib64/perl5/auto/Encode/CN/CN.so
dangling: /usr/lib/.build-id/55/4466f3ba07d8c68e182f4664bea89edc6ca977 -> ../../../../usr/lib64/perl5/auto/Encode/KR/KR.so
dangling: /usr/lib/.build-id/9b/b76a0d6b526ae41ae293e3a380965d6dfbcddb -> ../../../../usr/lib64/perl5/auto/Encode/Encode.so
dangling: /usr/lib/.build-id/e5/9f2cc2a60b3c93cb80f676cb10c33947fff9e1 -> ../../../../usr/lib64/perl5/auto/Filter/Util/Call/Call.so
dangling: /usr/lib/.build-id/1e/0069b4c149b951f05d0a5cc7e422c776fb3e41 -> ../../../../usr/lib64/python3.7/site-packages/gi/_gi_cairo.cpython-37m-x86_64-linux-gnu.so
dangling: /usr/lib/.build-id/36/2656ff4bc2e2d6cd08cd86aa629fecfb37e313 -> ../../../../usr/lib64/perl5/auto/Devel/Peek/Peek.so
dangling: /usr/lib/.build-id/f2/166998840d21e70379abff23a98988717afc3a -> ../../../../usr/lib64/perl5/auto/Digest/SHA/SHA.so
dangling: /usr/lib/.build-id/0d/af1e73e410de195ea920b2384fc69d410ec087 -> ../../../../usr/lib64/perl5/auto/List/Util/Util.so
dangling: /usr/lib/.build-id/d3/46ece08a996170f1e5033ba95d18e2254f54ed -> ../../../../usr/lib64/perl5/auto/Socket/Socket.so
dangling: /usr/lib/.build-id/69/74f3ebcf11fa8d9a19ee54eb50af14be2f42dc -> ../../../../usr/lib64/dovecot/doveadm/lib10_doveadm_sieve_plugin.so
dangling: /usr/lib/.build-id/69/9bacf31170b09a56bb033ede6581984d33c0f7 -> ../../../../usr/lib64/perl5/auto/Time/HiRes/HiRes.so
dangling: /usr/lib/.build-id/96/26d1666cace24a81ee5a77fe9e579258ac342e -> ../../../../usr/lib64/libncurses++w.so.6.1
dangling: /usr/lib/.build-id/5c/c6279fd36f22e35b83b0ac73356dc1a4d76df1 -> ../../../../usr/lib64/perl5/auto/Encode/Unicode/Unicode.so
dangling: /usr/lib/.build-id/9c/ff1249bda228d9278c9c347d0cab4437056810 -> ../../../../usr/lib64/perl5/auto/IPC/SysV/SysV.so
dangling: /usr/lib/.build-id/5e/213a5bf6193f8184edda1f6278c30a9acaf694 -> ../../../../usr/lib64/perl5/auto/Math/BigInt/FastCalc/FastCalc.so
dangling: /usr/lib/.build-id/53/f0c8286103cbd403235e800f53d4b023671916 -> ../../../../usr/lib64/dovecot/lib95_imap_sieve_plugin.so
dangling: /usr/lib/modules/5.3.11-300.fc31.x86_64/build -> /usr/src/kernels/5.3.11-300.fc31.x86_64
dangling: /usr/lib/modules/5.3.11-300.fc31.x86_64/source -> build
dangling: /usr/lib/lsb/install_initd -> ../../../sbin/chkconfig
dangling: /usr/lib/lsb/remove_initd -> ../../../sbin/chkconfig
dangling: /usr/lib/gcc/x86_64-redhat-linux/9/32/libasan.a -> ../../../i686-redhat-linux/9/libasan.a
dangling: /usr/lib/gcc/x86_64-redhat-linux/9/32/libatomic.a -> ../../../i686-redhat-linux/9/libatomic.a
dangling: /usr/lib/gcc/x86_64-redhat-linux/9/32/libgomp.so -> ../../../../libgomp.so.1.0.0
dangling: /usr/lib/gcc/x86_64-redhat-linux/9/32/libitm.a -> ../../../i686-redhat-linux/9/libitm.a
dangling: /usr/lib/gcc/x86_64-redhat-linux/9/32/libquadmath.a -> ../../../i686-redhat-linux/9/libquadmath.a
dangling: /usr/lib/gcc/x86_64-redhat-linux/9/32/libubsan.a -> ../../../i686-redhat-linux/9/libubsan.a
dangling: /usr/lib/gcc/x86_64-redhat-linux/9/32/libstdc++.a -> ../../../i686-redhat-linux/9/libstdc++.a
dangling: /usr/lib/gcc/x86_64-redhat-linux/9/32/libstdc++.so -> ../../../../libstdc++.so.6.0.27
dangling: /usr/lib/gcc/x86_64-redhat-linux/9/32/libstdc++fs.a -> ../../../i686-redhat-linux/9/libstdc++fs.a
dangling: /usr/lib/gcc/x86_64-redhat-linux/9/32/libsupc++.a -> ../../../i686-redhat-linux/9/libsupc++.a
dangling: /usr/share/doc/hunspell/README -> README.md
dangling: /usr/share/man/man7/gnupg2.7.gz -> gnupg.7.gz
dangling: /usr/share/man/man1/ex.1.gz -> vim.1.gz
dangling: /usr/share/man/man1/rview.1.gz -> vim.1.gz
dangling: /usr/share/man/man1/view.1.gz -> vim.1.gz
dangling: /usr/share/cockpit/branding/debian/favicon.ico -> /usr/share/pixmaps/debian-logo.png
dangling: /usr/share/cockpit/branding/debian/logo.png -> /usr/share/pixmaps/debian-logo.png
dangling: /usr/share/cockpit/branding/ubuntu/logo.png -> /usr/share/plymouth/ubuntu-logo.png