I'm using an Ubuntu 8.04 (x86_64) machine to connect to my employer's Cisco VPN. (The client didn't compile out of the box, but I found patches to update the client to compile on kernels released in the last two years.) This all works great, until my DHCP client decides to renew its lease and updates /etc/resolv.conf, replacing the VPN-specific name servers with my general network servers.
Is there a good way to prevent my DHCP client from updating /etc/resolv.conf while my VPN is active?
If you are running without NetworkManager handling the connections, use the resolvconf package to act as an intermediary to programs tweaking /etc/resolv.conf: sudo apt-get install resolvconf
If you are using NetworkManager it will handle this for you, so get rid of the resolvconf package: sudo apt-get remove resolvconf
I found out about this when setting up vpnc on Ubuntu last week. A search for vpn resolv.conf on ubuntuforums.org has 250 results, many of which are very related!
If you are using the Ubuntu default with NetworkManager, try removing the CiscoVPN client and use the NetworkManager vpnc plugin to connect to the Cisco VPN. This should avoid all problems, since NetworkManager then knows about your VPN connection.
I would advice following the advice from #Sean, but if that fails for whatever reason, it should be possible to configure dhclient to not request DNS servers in /etc/dhcp3/dhclient.conf
chattr +i /etc/resolv.conf should work. ( -i to undo )
But the better thing is to configure your dhclient.conf:
https://calomel.org/dhclient.html
Look at superceding domain-name-servers, and domain-name.
Also look at "send hostname;"
If it works at your work place, you will have a cool hostname for your PC and not some weird name that DHCP servers assign.
vpnc seems to be doing the right thing for my employer's cisco concentrator. I jump on and off the vpn, and it seems to update everything smoothly.
The DHCPclient daemon can be told not to update resolv.conf with a command line switch. (-r I think, depending on the client)
That's less dynamic, because you'd have to restart/reconfigure DHCP when you connect, but not too hard. Similarly, you could just stop the service, but you might lose your IP in the meantime, so I wouldn't really recommend that.
Alternatively, you could run the dhcpclient from within a cron job, adding the appropriate process checks.
This problem is much more noticeable on networks with low DHCP lease ages. There is a bug filed in Ubuntu's dhcp3 package launchpad:
https://bugs.launchpad.net/ubuntu/+source/dhcp3/+bug/90681
Which includes this patch in the description:
--- /sbin/dhclient-script.orig 2007-03-08 19:19:56.000000000 +0000
+++ /sbin/dhclient-script 2007-03-08 19:19:46.000000000 +0000
## -13,6 +13,10 ##
# The alias handling in here probably still sucks. -mdz
make_resolv_conf() {
+ # don't overwrite resolv.conf at RENEW time, since a VPN/PPTP tunnel may
+ # have updated it with remote DNS servers
+ [ "$reason" = "RENEW" ] && return
+
if [ -n "$new_domain_name" -o -n "$new_domain_name_servers" ]; then
# Find out whether we are going to mount / rw
exec 9>&0 </etc/fstab
This change to /sbin/dhcp-script stops DHCP client from overwriting /etc/resolv.conf when it renews its lease.
Related
I am trying to configure the headless VPN only FortiClient on an AWS ubuntu 20.04 ec2 instance, and though I am able to connect to the target, I am then disconnected from the instance and cannot progress.
Setup:
wget http://cdn.software-mirrors.com/forticlientsslvpn_linux_4.4.2328.tar.gz
tar -xzvf forticlientsslvpn_linux_4.4.2328.tar.gz
cd ./forticlientsslvpn/64bit/helper
sudo ./setup.linux.sh
# Accept license
cd ..
./forticlientsslvpn_cli --server serveraddress:port --vpnuser username
# Enter password
##Connected!
At this stage, I am booted out of the instance and cannot reconnect (requiring a soft restart of the instance to gain access again)
I can see that there is a configuration file at forticlientsslvpn/64bit/helper/config but I cannot find any documentation describing what can be configured there or whether it is something I should be concerned with.
The CLI itself doesn't take any other options other than:
forticlientsslvpn_cli [--proxy proxyaddress:proxyport] --server vpnserveraddress:vpnport [--proxyuser proxyuser] [--vpnuser vpnuser] [--pkcs12 pkcs12path] [--keepalive]
I would like to either:
Preserve my original SSH connection (and any future connections) so I can develop within the VPN or;
Limit the VPN to only package traffic that is going to a specific IP range (CIDR block)
I have found three different methods for installing the client (sudo apt install forticlient, sudo apt install -y openfortivpn, see above) and cannot navigate through them. I have looked into FortiClientLinuxGuide and installed that tool but couldn't find out how to configure it as a VPN instead (or where to add the configuration). Similar experience with the second one.
This seems to be the only documentation about how to configure the CLI and its just the bear minimum How to setup and install SSLVPN.
This post seems to be having the same problem ssh-telnet-disconnects and the solution looks like it would work if only I knew how to set that configuration.
alternatively, I have looked up split tunnel configuration which looks like it would be ideal but cannot work out how I would set that up. The documentation is only via the GUI Enable-split-tunnel-feature
I'm using WSL2 on Windows 10.
My dev stack is using a local webserver (localwp or wamp) on the host OS.
I use WSL2 as the main terminal (SSH, Git, SASS, automation tools, ...).
What I need is a way to connect to my host services (MySql) from the WSL2 system using a server name instead of a random IP address.
It is already possible for the Windows host to connect to WSL2 services with "localhost". Is there a solution to do it the other way?
You should use hostname.local to access Windows from WSL2 because that will use the correct IP. Note that hostname should be replaced with the result of the hostname command run in WSL2.
You can check the IP by running ping $(hostname).local from WSL2.
You also need to add a firewall rule to allow traffic from WSL2 to Windows. In an elevated PowerShell prompt run this:
New-NetFirewallRule -DisplayName "WSL" -Direction Inbound -InterfaceAlias "vEthernet (WSL)" -Action Allow
The command above should allow you to access anything exposed by Windows from WSL, no matter what port, however bear in mind that any apps you've launched get an automated rule created for them when you first launch them, blocking access from public networks (this is when you get a prompt from Windows Firewall, asking whether the app should be allowed to accept connections from public networks).
If you don't explicitly allow, they will be blocked by default, which also blocks connections from WSL. So you might need to find that inbound rule, and change it from block to allow (or just delete it).
See info here:
https://github.com/microsoft/WSL/issues/4585#issuecomment-610061194
Well, your title and your question body don't seem quite aligned.
The question title says "use localhost", but then in the body you say "using a server name."
Accessing the Windows 10 service via the name "localhost" from WSL2? Let's just go with "no". I can think of a possibility of how to make it work, but it would be complicated.
But I think the second is really what you are looking for, so a couple of options that I can think of for accessing the Windows host services by hostname in WSL2:
First, and hopefully the easiest, WSL2 supports mDNS (WSL1 did not), so you should be able to access the Windows host as {hostname}.local (where {hostname} is the name of the Windows host (literally, in bash, ping $(hostname).local, since the assigned WSL2 hostname is that of the host Windows 10 computer). That works for me. While I don't recall having to do anything special to enable this, this Super User answer seems to indicate that you have to turn it on manually.
The second option would be to add your Windows host IP to /etc/hosts. If your Windows IP is static, then you could just add it manually to /etc/hosts and be done. If it's dynamic, then you might want to script it. You can retrieve it from inside WSL2 via:
powershell.exe "(Test-Connection -ComputerName (hostname) -Count 1).IPV4Address.IPAddressToString" (and other methods) and then use something like sed to change /etc/hosts.
Add the following code to ~/.bashrc or ~/.zshrc, and then use winhost to access the host ip。
sed -i -e '/winhost/d' /etc/hosts
win_ip=$(cat /etc/resolv.conf | grep nameserver | awk '{ print $2 }')
win_host="$win_ip winhost"
echo $win_host >> /etc/hosts
The last time I was facing this issue,
I downgraded to WSL1, and all the connections started working perfectly.
You can use:
wsl --set-version Ubuntu 1
This is the easiest approach to fix all connection related issues in WSL2.
This seems to be a new issue with network-manager-openconect-gnome in Ubuntu 18.04+
I install sudo apt install network-manager-openconnect-gnome to get gnome integration with opeconnect and Cisco AnyConnect Compatible VPN (openconnect)
As an aside (which may actually be relevant) I do this to get *.local addresses to resolve:
sudo ln -sf /run/systemd/resolve/resolv.conf /etc/resolv.conf as per systemd docs
Move dns before mdns4_minimal in /etc/nsswitch.conf
If I connect to the VPN with openconnect through the gnome network manager, VPN addresses (sites for work) do not resolve. Regular sites continue to work as expected.
If I connect to the VPN with openconnect on the command line with sudo openconnect vpn.mycompany.com, VPN addresses (sites for work) do resolve. Regular sites continue to work as expected.
I thought I would check to see if there were any differences between /etc/resolv.conf with each of these VPN connection methods and sure enough, there is one:
openconnect on the command line (working):
##VPNC_GENERATED# -- this file is generated by vpnc
# and will be overwritten by vpnc
# as long as the above mark is intact
# This file is managed by man:systemd-resolved(8). Do not edit.
#
# This is a dynamic resolv.conf file for connecting local clients directly to
# all known uplink DNS servers. This file lists all configured search domains.
#
# Third party programs must not access this file directly, but only through the
# symlink at /etc/resolv.conf. To manage man:resolv.conf(5) in a different way,
# replace this symlink by a static file or a different symlink.
#
# See man:systemd-resolved.service(8) for details about the supported modes of
# operation for /etc/resolv.conf.
nameserver 10.10.10.10
nameserver 10.10.10.11
search broadband mycompany.com
openconnect gnome integration (not working):
# This file is managed by man:systemd-resolved(8). Do not edit.
#
# This is a dynamic resolv.conf file for connecting local clients directly to
# all known uplink DNS servers. This file lists all configured search domains.
#
# Third party programs must not access this file directly, but only through the
# symlink at /etc/resolv.conf. To manage man:resolv.conf(5) in a different way,
# replace this symlink by a static file or a different symlink.
#
# See man:systemd-resolved.service(8) for details about the supported modes of
# operation for /etc/resolv.conf.
nameserver 192.168.1.1
nameserver 10.10.10.10
nameserver 10.10.10.11
search broadband mycompany.com
If I remove (or comment out) the nameserver 192.168.1.1, which is the difference in content between the working and not working files... everything works as expected. I can resolve addresses within the company and regular sites work as expected.
This does not happen with Fedora. Everything works out of the box. I'm not sure why the network-manager-openconnect-gnome package works differently or if there's a way I can make it work without either
Editing the file by hand.
Using the openconnect tool from the command line and keeping a terminal open running that command.
In a linux system, I suppose you can configure hostname to IP address mapping in /etc/hosts, but I guess if you change the mapping for a particular hostname, you would have to restart for the change to take effect.
Is there a way to dynamically (without restarting) change the mapping of a hostname to a different IP address?
In linux, administrators can specify the order of the source that an application will ask domain name information.
This file is
/etc/nsswitch.conf
and the default setting for dns is:
hosts: files dns
so yes you can add your sites in /etc/hosts and your application will follow that order. You dont need to restart and yes you can do it dynamically.
For more info type:
man nsswitch.conf
although there is a way for your application to bypass this feature. And that is when the application can "ask for dns" through a remote point or if the application havent built to use the operating system gethostbyname/gethostbyaddr system calls.
You just need to change the IP address in the /etc/hosts. Most of the time this change will propagate into the NS cache automatically. However, sometimes you just need to flush the name-server cache on your system. Depending on what you've got running the actual steps may vary. I'll list a few popular ones:
NSCD
$ sudo /etc/init.d/nscd restart
OR
$ sudo service nscd restart
OR
$ sudo systemctl restart nscd
dnsmasq
$ sudo /etc/init.d/dnsmasq restart
OR
$ sudo service dnsmasq restart
OR
$ sudo systemctl restart dnsmasq
BIND server dns cache
unrelated to OP question but in case someone ends up here
$ sudo rndc restart
OR
$ sudo rndc flushname foo.local
Where foo.local is the particular hostname you wish to r
So, I tried to set up a public SMB share with Samba on CentOS 7. Now, I have it set up, and I have a headache. But, sweet victory. I'm posting this here for all y'all so that you don't need to waste your time. It's actually easy, you just need to know the hoops you need to jump through. I'll also edit the Samba wiki.
The first problem was that it wouldn't connect at all, except locally:
Remote Connection (my Linux desktop):
-------
[root#my-desktop ~]# smbclient //sambaserver/PublicDocs -N
Error connecting to 192.168.100.97 (No route to host)
Connection to cgybkp01 failed (Error NT_STATUS_HOST_UNREACHABLE)
On Windows 8, using Windows Explorer, after typing "\\sambaserver" into the address bar, the progress bar would wait, wait, wait, then time out. The error message was:
Remote Connection (my Windows 8 desktop):
Windows cannot access \\sambaserver
Check the spelling of the name. Otherwise, there might be a problem with your network. To
try to identify and resolve network problems, click Diagnose.
This ended up being a problem with firewalld. To unblock Samba, I needed to add this line to /etc/firewalld/zones/public.xml :
<service name="samba"/>
Perfect, now I can connect!
But, I was actually mounting an NFS share, so I had one more issue, with SELinux. Now, when I attempt to connect with smbclient...
smbclient //sambaserver/PublicDocs -N
I can connect, but when I try to ls, I get the error: "NT_STATUS_ACCESS_DENIED" in CentOS 7. So, how do I connect?
The first thing everyone recommended that I try was file permissions. If you're not familiar with file permissions in Linux, I'd recommend trying those first. But for me, that didn't work, because SELinux was blocking me.
To see all of the SELinux options for Samba, type:
getsebool -a | grep samba
getsebool -a | grep smb
The one I needed to change was samba_share_nfs, because I was sharing an NFS mounted directory:
setsebool -P samba_share_nfs on
CentOS maintains a list of these booleans here.