vsftpd frequently asked questions
2024-07-21 02:34:53
供稿：网友
Q) Can I restrict users to their home Directories?
A) Yes. You are PRobably after the setting:
chroot_local_user=YES
Q) Does vsFTPd support a limit on the number of users connected?
A1) Yes, indirectly. vsftpd is an inetd-based service. If use the popular
"xinetd" as your inetd, this supports per-service per-ip connection limits.
There is an example of this in the "EXAMPLE" directory.
A2) If you run vsftpd in "standalone" mode with the setting listen=YES, then
you can investigate the setting (e.g.):
max_clients=10
Q) Help! I'm getting the error message "refusing to run with writable anonymous
root".
A) vsftpd is protecting against dangerous configurations. The cause of this
message is usually dodgy ownership of the ftp home directory. The home
directory should NOT be owned by the ftp user itself. Neither should it
be writable by the ftp user. A way to fix this is:
chown root ~ftp; chmod -w ~ftp
Q) Help! I'm getting the error message "str_getpwnam".
A) The most likely cause of this is that the "nobody" user does not exist on
your system. vsftpd needs this user to run bits of itself with no privilege.
Q) Help! Local users cannot log in.
A) There are various possible problems.
A1) By default, vsftpd disables any logins other than anonymous logins. Put
local_enable=YES in your /etc/vsftpd.conf to allow local users to log in.
A2) vsftpd tries to link with PAM. (Run "ldd vsftpd" and look for libpam to
find out whether this has happened or not). If vsftpd links with PAM, then
you will need to have a PAM file installed for the vsftpd service. There is
a sample one for RedHat systems included in the "RedHat" directory - put it
under /etc/pam.d
A3) If vsftpd didn't link with PAM, then there are various possible issues. Is
the user's shell in /etc/shells? If you have shadowed passWords, does your
system have a "shadow.h" file in the include path?
A4) If you are not using PAM, then vsftpd will do its own check for a valid
user shell in /etc/shells. You may need to disable this if you use an invalid
shell to disable logins other than FTP logins. Put check_shell=NO in your
/etc/vsftpd.conf.
Q) Help! Uploads or other write commands give me "500 Unknown command.".
A) By default, write commands, including uploads and new directories, are
disabled. This is a security measure. To enable writes, put write_enable=YES
in your /etc/vsftpd.conf.
Q) Help!
What are the security implications referred to in the
"chroot_local_user" option?
A) Firstly note that other ftp daemons have the same implications. It is a
generic problem.
The problem isn't too severe, but it is this: Some people have FTP user
accounts which are not trusted to have full shell access. If these
accounts can also upload files, there is a small risk. A bad user now has
control of the filesystem root, which is their home directory. The ftp
daemon might cause some config file to be read - e.g. /etc/some_file. With
chroot(), this file is now under the control of the user. vsftpd is
careful in this area. But, the system's libc might want to open locale
config files or other settings...
Q) Help! Uploaded files are appearing with permissions -rw-------.
A) Depending on if this is an upload by a local user or an anonymous user,
use "local_umask" or "anon_umask" to change this. For example, use
"anon_umask=022" to give anonymously uploaded files permissions
-rw-r--r--. Note that the "0" before the "22" is important.
Q) Help! How do I integrate with LDAP users and logins?
A) Use vsftpd's PAM integration to do this, and have PAM authenticate against
an LDAP repository.
Q) Help! Does vsftpd do virtual hosting setups?
A1) Yes. If you integrate vsftpd with xinetd, you can use xinetd to bind to
several different IP addresses. For each IP address, get xinetd to launch
vsftpd with a different config file. This way, you can get different behaviour
per virtual address.
A2) Alternatively, run as many copies as vsftpd as necessary, in standalone
mode. Use "listen_address=x.x.x.x" to set the virtual IP.
Q) Help! Does vsftpd support virtual users?
A) Yes, via PAM integration. Set "guest_enable=YES" in /etc/vsftpd.conf. This
has the effect of mapping every non-anonymous sUCcessful login to the local
username specified in "guest_username". Then, use PAM and (e.g.) its pam_userdb
module to provide authentication against an external (i.e. non-/etc/passwd)
repository of users.
Note - currently there is a restriction that with guest_enable enabled, local
users also get mapped to guest_username.
There is an example of virtual users setup in the "EXAMPLE" directory.
Q) Help! Does vsftpd support different settings for different users?
A) Yes - in a very powerful way. Look at the setting "user_config_dir" in the
manual page.
Q) Help! Can I restrict vsftpd data connections to a specific range of ports?
A) Yes. See the config settings "pasv_min_port" and "pasv_max_port".
Q) Help! I'm getting the message "OOPS: chdir".
A) If this is for an anonymous login,
check that the home directory for the
user "ftp" is correct. If you are using the config setting "anon_root", check
that is correct too
