An average guy's IT (mis)adventures

Using the Maildir mailbox format, emails are stored in under the recipient user’s home folder /home/<username>/Maildir.

# postconf -e 'home_mailbox = Maildir/'

You might also want to add the Maildir setup to the user home directory template so that it is automatically configured when a new user account is created:

# maildirmake.dovecot /etc/skel/Maildir
# maildirmake.dovecot /etc/skel/Maildir/.Drafts
# maildirmake.dovecot /etc/skel/Maildir/.Sent
# maildirmake.dovecot /etc/skel/Maildir/.Trash
# maildirmake.dovecot /etc/skel/Maildir/.Templates

The same Maildir can be added to the current user with the commands below. Replace the $USER with any existing username:

# cp -r /etc/skel/Maildir /home/$USER/
# chown -R $USER:$USER /home/$USER/Maildir
# chmod -R 700 /home/$USER/Maildir
# adduser $USER mail

Also create a “.muttrc” file under /etc/skel and copy paste this content in it:

set mbox_type=Maildir
set folder="~/Maildir"
set mask="!^\\.[^.]"
set mbox="~/Maildir"
set record="+.Sent"
set postponed="+.Drafts"
set spoolfile="~/Maildir"

I'm going to paste my working Monit configuration file for anyone attempting to make it work under Debian

  set daemon  120
  set log /var/log/monit.log
  set idfile /var/lib/monit/id
  set statefile /var/lib/monit/state

set ssl {
     verify     : enable
 }

  SET MAILSERVER
        pandora.woodpeckersnest.space
        PORT 465
        USERNAME <username> PASSWORD <password>
        using SSL

  set eventqueue
     basedir /var/lib/monit/events
     slots 100

  set alert <username>@woodpeckersnest.space not on { instance }

  set httpd port 2812 and
   use address 0.0.0.0
   allow 0.0.0.0/0.0.0.0
   allow admin:<password>
   with ssl {
         pemchain: /etc/monit/fullchain.pem
         pemkey: /etc/monit/privkey.pem
        }

  check system PANDORA
    if cpu usage > 95% for 10 cycles then alert
    if memory usage > 85% then alert
    if swap usage > 50% then alert

  check network ens3 with interface ens3
    if link down then alert
    if changed link then alert
    if saturation > 90% then alert

  check filesystem rootfs with path /
    if space usage > 80% then alert
    if space usage > 85% then alert
    if space usage > 90% then alert
    if space usage > 95% then alert

  check host pandora.spacenest.it with address 94.143.138.27
    if failed ping then alert
    if failed port 22 protocol ssh
    then alert

Then there are files under /etc/monit/conf.d/* and/or /etc/monit/conf-enabled/*. I only have 3:

nginx:

 check process nginx with pidfile /var/run/nginx.pid
   group www-data
   start program = "/etc/init.d/nginx start"
   stop program = "/etc/init.d/nginx stop"

postfix:

 check process postfix with pidfile /var/spool/postfix/pid/master.pid
     start program = "/etc/init.d/postfix start"
     stop  program = "/etc/init.d/postfix stop"
     if failed
        port 25
        protocol smtps
        username "<your_username>"
        password "<your_password>"
     then alert

sshd:

 check process sshd with pidfile /var/run/sshd.pid
   start program  "/etc/init.d/sshd start"
   stop program  "/etc/init.d/sshd stop"
   if failed port 22 protocol ssh then restart

Monit manual is very helpful, you should check it out.

Swap File

1. To create a 2GB swap file we can use "dd" command like this:

# dd if=/dev/zero of=/mnt/swapfile bs=1024 count=2097152

bs=1024 means read and write up to 1024 bytes at a time and count it's the size of the file (1024 x 2048)MB

2. Then set the appropriate permissions on the file; make it readable only by root user:

# chmod 600 /mnt/swapfile

3. Now prepare the file for swap with the mkswap command:

# mkswap /mnt/swapfile

4. Next, enable the swap file

# swapon /mnt/swapfile

5. Afterwards, enable the swap file to be mounted at boot. Edit the /etc/fstab file and add the following new line in it:

/mnt/swapfile swap swap defaults 0 0

You can also disable the swapfile at runtime, any time you want; just make sure it doesn't exceed your available RAM:

# swapoff /mnt/swapfile

Last but not least, this is how to check your swap usage by process:

$ for file in /proc/*/status ; do awk '/VmSwap|Name/{printf $2 " " $3}END{ print ""}' $file; done | sort -k 2 -n -r | less