Linux/Unix

OpenDKIM with Postfix (Centos 7)

Posted on by Andy

First install OpenDKIM: 

# yum install opendkim

Configure OpenDKIM (please read the comments inside the original config file): 

# vim /etc/opendkim.conf

PidFile /var/run/opendkim/opendkim.pid
Mode    sv
Syslog  yes
SyslogSuccess   yes
LogWhy  yes
UserID  opendkim:opendkim
Socket  inet:8891@localhost
Umask   002
SendReports     yes
SoftwareHeader  yes
Canonicalization        relaxed/simple
Selector        default
MinimumKeyBits  1024
KeyTable        /etc/opendkim/KeyTable
SigningTable    refile:/etc/opendkim/SigningTable
ExternalIgnoreList      refile:/etc/opendkim/TrustedHosts
InternalHosts   refile:/etc/opendkim/TrustedHosts
OversignHeaders From
SignatureAlgorithm      rsa-sha256

Generate a domain key + domain cert: 

# cd /etc/opendkim/keys
# opendkim-genkey -d mydomain.com
# mv default.private mydomain.private
# mv default.txt mydomain.txt
# chown opendkim:opendkim mydomain.*

Add the key to the keytable: 

# vim /etc/opendkim/KeyTable
>> default._domainkey.mydomain.com mydomain.com:default:/etc/opendkim/keys/mydomain.private

Add the cert to the SignTable 

# vim /etc/opendkim/SignTable
>> *@mydomain.com default._domainkey.mydomain.com

Edit postfix config and add OpenDKIM to the milters: 

# vim /etc/postfix/main.cf
>> smtpd_milters = inet:localhost:8891
>> non_smtpd_milters = inet:localhost:8891

Start OpenDKIM: 

# systemctl start opendkim
# systemctl enable opendkim

Restart postfix: 

# systemctl restart postfix

Add DKIM TXT record to DNS (Bind9): 

# vim /var/named/mydomain.com
>> default._domainkey.mydomain.com. 3600      TXT        "v=DKIM1; k=rsa; p=<very long string taken from /etc/opendkim/keys/mydomain.txt>"

Restart Bind: 

# systemctl restart named

Well, that should be it, wokring DKIM on your mydomain.com!

Install and mount HGFS share with open-vm-tools in Ubuntu 16.04 LTS

Posted on by Andy

First install the right open-vm-tools package: 

# sudo apt-get install open-vm-tools-dkms

then you can mount the shared folder with following command: 

# sudo mount -t fuse.vmhgfs-fuse .host:/ <mount point> -o allow_other

please make sure that the mount point exists. to make this permanent and mount at boot, edit your /etc/fstab file and add 

.host:/ /mnt/hgfs fuse.vmhgfs-fuse allow_other 0 0

Important: FUSE can only be used with kernel >4 and open-vm-tools >10, otherwise the simplest solution is to install VMware Tools

SSH tunnel

Posted on by Andy

how to open an SSH tunnel through another host: 

# ssh -l <user> -L <local_port>:<remote_host>:<remote_port> <host_to_connect>

this can be chained through multiple hosts, e.g.

# ssh -l user1 -L 80:localhost.1234 server1 (type on local machine)
# ssh -l user2 -L 1234:localhost:80 server2 (type on server1)

now server2's port can be reached through http://localhost