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I have a VPS Server running with openVZ and CentOs 6 and I want to install openVPN on it. I followed this tutorial: https://www.digitalocean.com/community/tutorials/how-to-setup-and-configure-an-openvpn-server-on-centos-6 but I'm not able to start the openVPN service:

Starting openvpn:                                          [FAILED]

Thats is whats inside my /var/log/messages/ file:

Mar  9 10:50:50 s18194633 openvpn[19715]: event_wait : Interrupted system call (code=4)
Mar  9 10:50:50 s18194633 openvpn[19715]: /sbin/ip route del 10.8.0.0/24
Mar  9 10:50:50 s18194633 openvpn[19715]: ERROR: Linux route delete command failed: external program exited with error status: 2
Mar  9 10:50:50 s18194633 openvpn[19715]: Closing TUN/TAP interface
Mar  9 10:50:50 s18194633 openvpn[19715]: /sbin/ip addr del dev tun0 local 10.8.0.1 peer 10.8.0.2
Mar  9 10:50:50 s18194633 openvpn[19715]: Linux ip addr del failed: external program exited with error status: 2
Mar  9 10:50:50 s18194633 openvpn[19715]: SIGTERM[hard,] received, process exiting
Mar  9 10:50:52 s18194633 openvpn[19753]: Options error: --cert fails with 'client.crt': No such file or directory
Mar  9 10:50:52 s18194633 openvpn[19753]: Options error: --key fails with 'client.key': No such file or directory
Mar  9 10:50:52 s18194633 openvpn[19753]: Options error: Please correct these errors.
Mar  9 10:50:52 s18194633 openvpn[19753]: Use --help for more information.
Mar  9 10:50:52 s18194633 openvpn[19756]: OpenVPN 2.3.6 x86_64-redhat-linux-gnu [SSL (OpenSSL)] [LZO] [EPOLL] [PKCS11] [MH] [IPv6] built on Dec  2 2014
Mar  9 10:50:52 s18194633 openvpn[19756]: library versions: OpenSSL 1.0.1e-fips 11 Feb 2013, LZO 2.03
Mar  9 10:50:52 s18194633 openvpn[19756]: Diffie-Hellman initialized with 2048 bit key
Mar  9 10:50:52 s18194633 openvpn[19756]: Socket Buffers: R=[133120->131072] S=[133120->131072]
Mar  9 10:50:52 s18194633 openvpn[19756]: ROUTE_GATEWAY ON_LINK IFACE=venet0 HWADDR=00:00:00:00:00:00
Mar  9 10:50:52 s18194633 openvpn[19756]: TUN/TAP device tun0 opened
Mar  9 10:50:52 s18194633 openvpn[19756]: TUN/TAP TX queue length set to 100
Mar  9 10:50:52 s18194633 openvpn[19756]: do_ifconfig, tt->ipv6=0, tt->did_ifconfig_ipv6_setup=0
Mar  9 10:50:52 s18194633 openvpn[19756]: /sbin/ip link set dev tun0 up mtu 1500
Mar  9 10:50:52 s18194633 openvpn[19756]: /sbin/ip addr add dev tun0 local 10.8.0.1 peer 10.8.0.2
Mar  9 10:50:52 s18194633 openvpn[19756]: /sbin/ip route add 10.8.0.0/24 via 10.8.0.2
Mar  9 10:50:52 s18194633 openvpn[19764]: GID set to nobody
Mar  9 10:50:52 s18194633 openvpn[19764]: UID set to nobody
Mar  9 10:50:52 s18194633 openvpn[19764]: UDPv4 link local (bound): [undef]
Mar  9 10:50:52 s18194633 openvpn[19764]: UDPv4 link remote: [undef]
Mar  9 10:50:52 s18194633 openvpn[19764]: MULTI: multi_init called, r=256 v=256
Mar  9 10:50:52 s18194633 openvpn[19764]: IFCONFIG POOL: base=10.8.0.4 size=62, ipv6=0
Mar  9 10:50:52 s18194633 openvpn[19764]: IFCONFIG POOL LIST
Mar  9 10:50:52 s18194633 openvpn[19764]: Initialization Sequence Completed

Do I have forgotten to do something?

The log says that it can't find client.crt and client.key but they are in the /etc/openvpn/easy-rsa/keys/folder

Also, if I do sysctl -p I get this error:

net.ipv4.ip_forward = 1
net.ipv4.tcp_syncookies = 1
error: "net.bridge.bridge-nf-call-ip6tables" is an unknown key
error: "net.bridge.bridge-nf-call-iptables" is an unknown key
error: "net.bridge.bridge-nf-call-arptables" is an unknown key

Doing sysctl -e -p seems to work, but I don't know if this fixes these errors. Can this have something to do with the error when I want to start openVPN?

Didn't this should create those missing files? Or am I missing something else?

This is my /etc/openvpn/server.conf:

#################################################
# Sample OpenVPN 2.0 config file for            #
# multi-client server.                          #
#                                               #
# This file is for the server side              #
# of a many-clients <-> one-server              #
# OpenVPN configuration.                        #
#                                               #
# OpenVPN also supports                         #
# single-machine <-> single-machine             #
# configurations (See the Examples page         #
# on the web site for more info).               #
#                                               #
# This config should work on Windows            #
# or Linux/BSD systems.  Remember on            #
# Windows to quote pathnames and use            #
# double backslashes, e.g.:                     #
# "C:\\Program Files\\OpenVPN\\config\\foo.key" #
#                                               #
# Comments are preceded with '#' or ';'         #
#################################################

# Which local IP address should OpenVPN
# listen on? (optional)
;local a.b.c.d

# Which TCP/UDP port should OpenVPN listen on?
# If you want to run multiple OpenVPN instances
# on the same machine, use a different port
# number for each one.  You will need to
# open up this port on your firewall.
port 1194

# TCP or UDP server?
;proto tcp
proto udp

# "dev tun" will create a routed IP tunnel,
# "dev tap" will create an ethernet tunnel.
# Use "dev tap0" if you are ethernet bridging
# and have precreated a tap0 virtual interface
# and bridged it with your ethernet interface.
# If you want to control access policies
# over the VPN, you must create firewall
# rules for the the TUN/TAP interface.
# On non-Windows systems, you can give
# an explicit unit number, such as tun0.
# On Windows, use "dev-node" for this.
# On most systems, the VPN will not function
# unless you partially or fully disable
# the firewall for the TUN/TAP interface.
;dev tap
dev tun

# Windows needs the TAP-Win32 adapter name
# from the Network Connections panel if you
# have more than one.  On XP SP2 or higher,
# you may need to selectively disable the
# Windows firewall for the TAP adapter.
# Non-Windows systems usually don't need this.
;dev-node MyTap

# SSL/TLS root certificate (ca), certificate
# (cert), and private key (key).  Each client
# and the server must have their own cert and
# key file.  The server and all clients will
# use the same ca file.
#
# See the "easy-rsa" directory for a series
# of scripts for generating RSA certificates
# and private keys.  Remember to use
# a unique Common Name for the server
# and each of the client certificates.
#
# Any X509 key management system can be used.
# OpenVPN can also use a PKCS #12 formatted key file
# (see "pkcs12" directive in man page).
ca ca.crt
cert server.crt
key server.key  # This file should be kept secret

# Diffie hellman parameters.
# Generate your own with:
#   openssl dhparam -out dh2048.pem 2048
dh dh2048.pem

# Network topology
# Should be subnet (addressing via IP)
# unless Windows clients v2.0.9 and lower have to
# be supported (then net30, i.e. a /30 per client)
# Defaults to net30 (not recommended)
;topology subnet

# Configure server mode and supply a VPN subnet
# for OpenVPN to draw client addresses from.
# The server will take 10.8.0.1 for itself,
# the rest will be made available to clients.
# Each client will be able to reach the server
# on 10.8.0.1. Comment this line out if you are
# ethernet bridging. See the man page for more info.
server 10.8.0.0 255.255.255.0

# Maintain a record of client <-> virtual IP address
# associations in this file.  If OpenVPN goes down or
# is restarted, reconnecting clients can be assigned
# the same virtual IP address from the pool that was
# previously assigned.
ifconfig-pool-persist ipp.txt

# Configure server mode for ethernet bridging.
# You must first use your OS's bridging capability
# to bridge the TAP interface with the ethernet
# NIC interface.  Then you must manually set the
# IP/netmask on the bridge interface, here we
# assume 10.8.0.4/255.255.255.0.  Finally we
# must set aside an IP range in this subnet
# (start=10.8.0.50 end=10.8.0.100) to allocate
# to connecting clients.  Leave this line commented
# out unless you are ethernet bridging.
;server-bridge 10.8.0.4 255.255.255.0 10.8.0.50 10.8.0.100

# Configure server mode for ethernet bridging
# using a DHCP-proxy, where clients talk
# to the OpenVPN server-side DHCP server
# to receive their IP address allocation
# and DNS server addresses.  You must first use
# your OS's bridging capability to bridge the TAP
# interface with the ethernet NIC interface.
# Note: this mode only works on clients (such as
# Windows), where the client-side TAP adapter is
# bound to a DHCP client.
;server-bridge

# Push routes to the client to allow it
# to reach other private subnets behind
# the server.  Remember that these
# private subnets will also need
# to know to route the OpenVPN client
# address pool (10.8.0.0/255.255.255.0)
# back to the OpenVPN server.
;push "route 192.168.10.0 255.255.255.0"
;push "route 192.168.20.0 255.255.255.0"
push "redirect-gateway def1 bypass-dhcp"
push "dhcp-option DNS 8.8.8.8"
push "dhcp-option DNS 8.8.4.4"

# To assign specific IP addresses to specific
# clients or if a connecting client has a private
# subnet behind it that should also have VPN access,
# use the subdirectory "ccd" for client-specific
# configuration files (see man page for more info).

# EXAMPLE: Suppose the client
# having the certificate common name "Thelonious"
# also has a small subnet behind his connecting
# machine, such as 192.168.40.128/255.255.255.248.
# First, uncomment out these lines:
;client-config-dir ccd
;route 192.168.40.128 255.255.255.248
# Then create a file ccd/Thelonious with this line:
#   iroute 192.168.40.128 255.255.255.248
# This will allow Thelonious' private subnet to
# access the VPN.  This example will only work
# if you are routing, not bridging, i.e. you are
# using "dev tun" and "server" directives.

# EXAMPLE: Suppose you want to give
# Thelonious a fixed VPN IP address of 10.9.0.1.
# First uncomment out these lines:
;client-config-dir ccd
;route 10.9.0.0 255.255.255.252
# Then add this line to ccd/Thelonious:
#   ifconfig-push 10.9.0.1 10.9.0.2

# Suppose that you want to enable different
# firewall access policies for different groups
# of clients.  There are two methods:
# (1) Run multiple OpenVPN daemons, one for each
#     group, and firewall the TUN/TAP interface
#     for each group/daemon appropriately.
# (2) (Advanced) Create a script to dynamically
#     modify the firewall in response to access
#     from different clients.  See man
#     page for more info on learn-address script.
;learn-address ./script

# If enabled, this directive will configure
# all clients to redirect their default
# network gateway through the VPN, causing
# all IP traffic such as web browsing and
# and DNS lookups to go through the VPN
# (The OpenVPN server machine may need to NAT
# or bridge the TUN/TAP interface to the internet
# in order for this to work properly).
;push "redirect-gateway def1 bypass-dhcp"

# Certain Windows-specific network settings
# can be pushed to clients, such as DNS
# or WINS server addresses.  CAVEAT:
# http://openvpn.net/faq.html#dhcpcaveats
# The addresses below refer to the public
# DNS servers provided by opendns.com.
;push "dhcp-option DNS 208.67.222.222"
;push "dhcp-option DNS 208.67.220.220"

# Uncomment this directive to allow different
# clients to be able to "see" each other.
# By default, clients will only see the server.
# To force clients to only see the server, you
# will also need to appropriately firewall the
# server's TUN/TAP interface.
;client-to-client

# Uncomment this directive if multiple clients
# might connect with the same certificate/key
# files or common names.  This is recommended
# only for testing purposes.  For production use,
# each client should have its own certificate/key
# pair.
#
# IF YOU HAVE NOT GENERATED INDIVIDUAL
# CERTIFICATE/KEY PAIRS FOR EACH CLIENT,
# EACH HAVING ITS OWN UNIQUE "COMMON NAME",
# UNCOMMENT THIS LINE OUT.
;duplicate-cn

# The keepalive directive causes ping-like
# messages to be sent back and forth over
# the link so that each side knows when
# the other side has gone down.
# Ping every 10 seconds, assume that remote
# peer is down if no ping received during
# a 120 second time period.
keepalive 10 120

# For extra security beyond that provided
# by SSL/TLS, create an "HMAC firewall"
# to help block DoS attacks and UDP port flooding.
#
# Generate with:
#   openvpn --genkey --secret ta.key
#
# The server and each client must have
# a copy of this key.
# The second parameter should be '0'
# on the server and '1' on the clients.
;tls-auth ta.key 0 # This file is secret

# Select a cryptographic cipher.
# This config item must be copied to
# the client config file as well.
;cipher BF-CBC        # Blowfish (default)
;cipher AES-128-CBC   # AES
;cipher DES-EDE3-CBC  # Triple-DES

# Enable compression on the VPN link.
# If you enable it here, you must also
# enable it in the client config file.
comp-lzo

# The maximum number of concurrently connected
# clients we want to allow.
;max-clients 100

# It's a good idea to reduce the OpenVPN
# daemon's privileges after initialization.
#
# You can uncomment this out on
# non-Windows systems.
user nobody
group nobody

# The persist options will try to avoid
# accessing certain resources on restart
# that may no longer be accessible because
# of the privilege downgrade.
persist-key
persist-tun

# Output a short status file showing
# current connections, truncated
# and rewritten every minute.
status openvpn-status.log

# By default, log messages will go to the syslog (or
# on Windows, if running as a service, they will go to
# the "\Program Files\OpenVPN\log" directory).
# Use log or log-append to override this default.
# "log" will truncate the log file on OpenVPN startup,
# while "log-append" will append to it.  Use one
# or the other (but not both).
;log         openvpn.log
;log-append  openvpn.log

# Set the appropriate level of log
# file verbosity.
#
# 0 is silent, except for fatal errors
# 4 is reasonable for general usage
# 5 and 6 can help to debug connection problems
# 9 is extremely verbose
verb 3

# Silence repeating messages.  At most 20
# sequential messages of the same message
# category will be output to the log.
;mute 20

Thats the output from ls -la /etc/openvpn:

drwxr-xr-x  4 root    root   4096  9. Mär 10:50 .
drwxr-xr-x 80 root    root   4096  9. Mär 12:44 ..
-rw-r--r--  1 root    root   1781  9. Mär 10:10 ca.crt
-rw-r--r--  1 root    root   3441 17. Feb 21:55 client.conf
-rw-r--r--  1 root    root   3441 17. Feb 21:55 client.ovpn
-rw-r--r--  1 root    root    424  9. Mär 10:10 dh2048.pem
drwxr-xr-x  3 root    root   4096  9. Mär 10:33 easy-rsa
drwxrwxr-x  3 openvpn games  4096 17. Feb 21:48 EasyRSA-2.2.2
-rw-r--r--  1 root    root  10492 11. Nov 2013  EasyRSA-2.2.2.tgz
-rw-------  1 root    root      0 17. Feb 22:02 ipp.txt
-rw-------  1 root    root    232  9. Mär 13:01 openvpn-status.log
-rw-r--r--  1 root    root  10542  9. Mär 09:32 server.conf
-rw-r--r--  1 root    root   5576  9. Mär 10:10 server.crt
-rw-------  1 root    root   1708  9. Mär 10:10 server.key
-rw-------  1 root    root    636  9. Mär 10:50 static.key
  • build-key creates the certificates. Have you followed all the steps in that document under the section "Configuring OpenVPN Client"? – roaima Mar 9 '15 at 11:02
  • No, I stopped after service openvpn start failed. Does it makes sense to start configuration of the client if the server can't even start? – Peter Mar 9 '15 at 11:10
  • I also added another error I get to my description. – Peter Mar 9 '15 at 11:16
  • There should be no reference to the client certificates on the server. – roaima Mar 9 '15 at 11:20
  • Okay, so I need to move the files client.crt, client.csr and client.key to the client and delete them from the server? But how do I delete the reference? – Peter Mar 9 '15 at 11:24
2

Your problem is that the service startup file for CentOS will try to run any config file that's in /etc/openvpn - after all, it has no way of knowing which was the intended config file.

Delete the client.conf file that's hanging around in that directory, or as raoima suggests move it to one side, and the openvpn startup script will stop trying to invoke it.

4

Use absolute path to point where each certificate/key is:

ca /etc/openvpn/easy-rsa/keys/ca.crt
cert /etc/openvpn/easy-rsa/keys/server.crt
key /etc/openvpn/easy-rsa/keys/server.key
dh /etc/openvpn/easy-rsa/keys/dh2048.pem

You can also start the OpenVPN server invoking it's own binary.

openvpn --config /etc/openvpn/server.conf --daemon

As roaima said, you must change the extension of your "client.conf" and any other "*.conf" file before using the CentOS startup script.

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