The following code allows e-mail to be sent to realtouser+rewriteuser+rewritedomain@smtp-rewrite.realdomain, and it will change the from address to rewritefrom@rewritedomain and send the mail to realtouser@realdomain

If requires the follwing postfix config in /etc/postfix/master.cf:

The following powershell can be used to renew an exchange certificate using the enterprise CA:

I have just finished troubleshooting an issue where DRBD was causing a bottleneck for an application (ddumbfs) that has an open mmaped file. The issue was that ddumbfs issues fsync() calls periodically on its mmaped files, and when these were happening I/O would pause while the data was being replicated.

The issue is partially fixed by increasing the max-buffers and max-epoch to the maximum values, to allow the maximum number of operations to be in-flight at any given point in time:

I have had issues for a while with upload speed to our samba server. I was able to download at ~70MB/s, but upload at only 7MB/s. From memory, I fixed the download speed by setting a bunch of settings, but uploads remained slow.

Tracing the issue led me to do a strace on the smbd process, which showed 1460 bytes being written every 0.2ms, with the read() and write() system calls using all the time. The end solution was to set the following option in /setc/samba/smb.conf

socket options = TCP_NODELAY


I have been re-configuring my home system to try and optimise the performance of the RAID volumes. I have just finished setting up a 6 disk RAID6 with a 64k stripe size (based on these benchmarks http://louwrentius.com/linux-raid-level-and-chunk-size-the-benchmarks.h…) and an external write-intent bitmap on an ext2 filesystem (to avoid any journal overheads).

I have had a look at a few SSD caching solutions, and had previously settled on enhanceio as the "best" option because it works on entire block devices and is easily added/removed. I have had some issues where the presence of enhanceio actually reduces performance because it caches every read/write, so backups, single file copies, etc are all cached even though they will never be looked at again.

I was recently involved in troubleshooting an issue where an on-premis exchange deployment was bouncing e-mails with an error that the user did not have an MDB assigned. This was a multi-tenant exchange deployment, so we could not use the official hybrid mode, but we were using one of the sync tools to keep usernames and passwords for the local users in sync with the office 365 users.

I have just got ipcomp working between 2 hosts as follows:

• Install the ipsec-tools program
• Add the following config to /etc/ipsec-tools.d/peername.conf
  
  spdadd MY_IP PEER_IP any -P out ipsec ipcomp/transport//use;
  add MY_IP PEER_IP ipcomp 1000 -m transport -C deflate;

  spdadd PEER_IP MY_IP any -P in ipsec ipcomp/transport//use;
  add PEER_IP MY_IP ipcomp 1000 -m transport -C deflate;
  

Use the quser command to find the session ID, then logoff to log the user off as follows:

To list all WMI performance counter sources, the following powershell command can be used:

Get-WmiObject -List


You can also have a look at the counters available using

Get-WmiObject -Class _ClassName_