There is a very important difference between the root
and the alias
directives. This difference exists in the way the path specified in the root
or the alias
is processed.
root
- the
location
part is appended toroot
part - final path =
root
+location
alias
- the
location
part is replaced by thealias
part - final path =
alias
To illustrate:
Let’s say we have the config
location /static/ {
root /var/www/app/static/;
autoindex off;
}
In this case the final path that Nginx will derive will be
/var/www/app/static/static
This is going to return 404
since there is no static/
within static/
This is because the location part is appended to the path specified in the root
. Hence, with root
, the correct way is
location /static/ {
root /var/www/app/;
autoindex off;
}
On the other hand, with alias
, the location part gets dropped. So for the config
location /static/ {
alias /var/www/app/static/;
autoindex off; ↑
} |
pay attention to this trailing slash
the final path will correctly be formed as
/var/www/app/static
In a way this makes sense. The alias
just let’s you define a new path to represent an existing “real” path. The location part is that new path, and so it gets replaced with the real path. Think of it as a symlink.
Root, on the other hand is not a new path, it contains some information that has to be collated with some other info to make the final path. And so, the location part is used, not dropped.
The case for trailing slash in alias
There is no definitive guideline about whether a trailing slash is mandatory per Nginx documentation, but a common observation by people here and elsewhere seems to indicate that it is.
A few more places have discussed this, not conclusively though.
https://serverfault.com/questions/375602/why-is-my-nginx-alias-not-working