Symlinks have limitations in how functions like ls, mv, and cp can operate on them because unlike shell initiated commands like cd, these functions do not have information about how the user accessed the directory with respect to the logical path (see related post). It seems like using the mount --bind option instead can get an around this, offering increased functionality and compatibility with samba and other file servers because the mounted directory will then have two independent physical paths, instead of a link.
I would like to replace all of my symbolic links with references using the mount --bind option but this would mean mounting over 150 points in fstab. Are there any performance issues that could potentially arise from this or any other drawbacks that I should consider?
Best Answer
With
mount --bind, a directory tree exists in two (or more) places in the directory hierarchy. This can cause a number of problems. Backups and other file copies will pick all copies. It becomes difficult to specify that you want to copy a filesystem: you'll end up copying the bind-mounted files twice. Searches withfind,grep -r,locate, etc., will traverse all the copies, and so on.You will not gain any “increased functionality and compatibility” with bind mounts. They look like any other directory, which most of the time is not desirable behavior. For example, Samba exposes symbolic links as directories by default; there is nothing to gain with using a bind mount. On the other hand, bind mounts can be useful to expose directory hierarchies over NFS.
You won't have any performance issues with bind mounts. What you'll have is administration headaches. Bind mounts have their uses, such as making a directory tree accessible from a chroot, or exposing a directory hidden by a mount point (this is usually a transient use while a directory structure is being remodeled). Don't use them if you don't have a need.
Only root can manipulate bind mounts. They can't be moved by ordinary means; they lock their location and the ancestor directories.
Generally speaking, if you pass a symbolic link to a command, the command acts on the link itself if it operates on files, and on the target of the link if it operates on file contents. This goes for directories too. This is usually the right thing. Some commands have options to treat symbolic links differently, for example
ls -L,cp -d,rsync -l. Whatever you're trying to do, it's far more likely that symlinks are the right tool, than bind mounts being the right tool.