How to use the command 'namei' (with examples)

The ’namei’ command is used to follow a pathname (which can be a symbolic link) until a terminal point is found, such as a file, directory, or character device. It is especially useful for finding “too many levels of symbolic links” problems. By executing the ’namei’ command with different options and arguments, we can resolve pathnames, display results, show file mode bits, show owner and group names, and control symlink resolution.

Use case 1: Resolve the pathnames specified as the argument parameters

Code:

namei path/to/a path/to/b path/to/c

Motivation: This use case is helpful when we want to determine the final destination of symbolic links in a given path. It allows us to navigate through symbolic links and find the actual files or directories they point to.

Explanation: The ’namei’ command takes the pathnames specified as the argument parameters and resolves them until a terminal point is found. It follows symbolic links in the path and displays the final destination. This can help identify the actual files or directories that symbolic links point to.

Example output:

$ namei path/to/a path/to/b path/to/c
   f: path/to/a
   d: path/to/b
   f: path/to/c

In the given example, the ’namei’ command resolves the pathnames ‘path/to/a’, ‘path/to/b’, and ‘path/to/c’. It displays ‘f’ for files and ’d’ for directories, along with the resolved path for each argument. In this case, ‘path/to/a’ is a file, ‘path/to/b’ is a directory, and ‘path/to/c’ is another file.

Use case 2: Display the results in a long-listing format

Code:

namei --long path/to/a path/to/b path/to/c

Motivation: Sometimes, it is useful to have detailed information about the resolved pathnames, such as file permissions, sizes, ownership, and modification times. By using the ‘–long’ option, we can obtain a long-listing format similar to the ’ls’ command.

Explanation: The ‘–long’ option is used to display the results of the ’namei’ command in a long-listing format. It provides detailed information about the resolved pathnames, including file mode bits, number of links, owner, group, file size, and modification time.

Example output:

$ namei --long path/to/a path/to/b path/to/c
   drwxrwxr-x. 2 user group  4096 Oct 10 10:00 path/to/a
   -rwxr-xr-x. 1 user group 10240 Oct 10 09:30 path/to/b
   -rw-rw-r--. 1 user group  2048 Oct 10 09:45 path/to/c

In the given example, the ’namei’ command displays the resolved pathnames ‘path/to/a’, ‘path/to/b’, and ‘path/to/c’ in a long-listing format. Each line represents a pathname along with its detailed information, such as file permissions, ownership, file size, and modification time.

Use case 3: Show the mode bits of each file type in the style of ’ls’

Code:

namei --modes path/to/a path/to/b path/to/c

Motivation: When dealing with symbolic links and other file types, it can be beneficial to view the mode bits similar to the ’ls’ command. By using the ‘–modes’ option, we can quickly determine the permissions and file type of each resolved pathname.

Explanation: The ‘–modes’ option is used to show the mode bits of each file type in the style of ’ls’. It displays the file permissions and the file type (directories are represented by ’d’, regular files by ‘-’, and symbolic links by ’l’) for each resolved pathname.

Example output:

$ namei --modes path/to/a path/to/b path/to/c
   drwxrwxr-x  path/to/a
   -rwxr-xr-x  path/to/b
   -rw-rw-r--  path/to/c

In the given example, the ’namei’ command shows the modes of pathnames ‘path/to/a’, ‘path/to/b’, and ‘path/to/c’. Each line represents a resolved pathname along with its mode bits (file permissions) and file type symbol.

Use case 4: Show owner and group name of each file

Code:

namei --owners path/to/a path/to/b path/to/c

Motivation: In certain situations, it can be valuable to know the owner and group name of files. The ‘–owners’ option allows us to quickly identify the ownership details of each resolved pathname.

Explanation: The ‘–owners’ option is used to display the owner and group name of each resolved file or directory. It gives us information about who owns the file and which group it belongs to.

Example output:

$ namei --owners path/to/a path/to/b path/to/c
   path/to/a  user  group
   path/to/b  user  group
   path/to/c  user  group

In the given example, the ’namei’ command shows the owner and group name for each resolved pathname. Each line represents a resolved pathname along with its owner and group details.

Use case 5: Don’t follow symlinks while resolving

Code:

namei --nosymlinks path/to/a path/to/b path/to/c

Motivation: In certain scenarios, we may want to stop symbolic link resolution and view the symbolic link itself instead of its resolved destination. The ‘–nosymlinks’ option helps in such cases by preventing the ’namei’ command from following symbolic links.

Explanation: The ‘–nosymlinks’ option is used to disable the follow-up of symbolic links while resolving the pathnames. It allows us to view the symbolic links themselves instead of their resolved destinations.

Example output:

$ namei --nosymlinks path/to/a path/to/b path/to/c
   slink path/to/a
   slink path/to/b
   -rw-rw-r-- path/to/c

In the given example, the ’namei’ command displays the pathnames ‘path/to/a’, ‘path/to/b’, and ‘path/to/c’ without resolving the symbolic links. The symbolic links are indicated by ‘slink’, and the non-symbolic link file is shown with its mode bits.

Conclusion:

The ’namei’ command is a versatile tool for resolving pathnames, navigating through symbolic links, and obtaining detailed information about files and directories. By using the various options, we can customize the output format and control symlink resolution according to our requirements.