How-to...

File: /etc/mail/aliases

root:               root@example.org

and then run :

localhost ~ # newaliases

localhost ~ # du -sh
65G     .

localhost ~ # du -sh *
756K    cache
24M     db
4.0K    empty
65G     lib
8.0K    lock
5.4M    log
0       mail
68K     run

localhost ~ # whereis sendmail

localhost ~ # grep -R -n1 "/usr/lib/sendmail" /etc
/etc/nail.rc-63-
/etc/nail.rc:64:# Use the local sendmail (/usr/lib/sendmail) binary by default.
/etc/nail.rc-65-# (Uncomment the following line to use a SMTP server)

localhost ~ # sysctl -a

as root :

localhost ~ # sysctl -w net.ipv4.tcp_keepalive_time=15
localhost ~ # sysctl -w net.ipv4.tcp_keepalive_probes=2
localhost ~ # sysctl -w net.ipv4.tcp_keepalive_intvl=10

to persist, edit /etc/sysctl.conf and reload file :

localhost ~ # sudo sysctl -p /etc/sysctl.conf

dump for an encrypted fs :

localhost ~ # hexdump -n 256 -C /dev/sda1
00000000  4c 55 4b 53 ba be 00 01  61 65 73 00 00 00 00 00  |LUKS....aes.....|

localhost ~ # mdadm --auto-detect
localhost ~ # cat /proc/mdstat

localhost ~ # netstat -apn | grep :4445
tcp        0      0 10.40.0.32:34251            10.40.0.33:4445             ESTABLISHED 31798/java
tcp        0      0 10.40.0.32:34252            10.40.0.33:4445             ESTABLISHED 31885/java
tcp        0      0 10.40.0.32:34253            10.40.0.33:4445             ESTABLISHED 31966/java
tcp        0      0 10.40.0.32:34260            10.40.0.33:4445             ESTABLISHED 32044/java

# Xvnc -alwaysshared -localhost -desktop MyName -geometry 4000x3000 -once securitytypes=none :2 &