You can create and mount a ram based disk as follows:

1. Create a disk:

   $ hdiutil attach -nomount ram://$((2 * 1024 * SIZE_IN_MB))

   hdiutil will return the name of the ramdisk.
2. Format and mount the disk diskutil eraseVolume HFS+ RAMDisk NAME_OF_DISK Creating a 100MB ramdisk:

   $ hdiutil attach -nomount ram://$((2 * 1024 * 100)) /dev/disk3

3. Started erase on disk3 Unmounting disk Erasing Initialized /dev/rdisk3 as a 100 MB case-insensitive HFS Plus volume Mounting disk Finished erase on disk3 RAMDisk:

   $ diskutil eraseVolume HFS+ RAMDisk /dev/disk3

Source: linux – Does OS X have an equivalent to /dev/shm? – Stack Overflow

The substitute command (:s) applies to whole lines, however the \%V atom will restrict a pattern so that it matches only inside the visual selection. This works with characterwise and blockwise selection (and is not needed with linewise selection). For example, put the cursor on this line:

music amuse fuse refuse

In normal mode, type ^wvee to visually select “amuse fuse” (^ goes to first nonblank character, w moves forward a word, v enters visual mode, e moves forward to end of next word). Then press Escape and enter the following command to change all “us” to “az” in the last-selected area within the current line:

:s/\%Vus/az/g

The result is:

music amaze faze refuse

Source: Search and replace in a visual selection – Vim Tips Wiki – Wikia

Problem solved ! Here is a pure sql solution, how to get all sql from all tables in Postgres:

--
--
-- NB 27.02.16
-- List sql tables
-- show_create_table()
--
--
SELECT
  'CREATE TABLE '||sql.table||'('
    ||array_to_string(array_agg(sql),', ')
  ||')' as sql
FROM (
  (
    SELECT -- FIELDS
      c.oid AS id
      ,c.relname as table
      ,9 as prio
      ,''
        || f.attname
        || ' ' || pg_catalog.format_type(f.atttypid,f.atttypmod)
        ||CASE WHEN f.attnotnull THEN ' NOT NULL' ELSE '' END
        ||CASE WHEN f.atthasdef = 't' AND d.adsrc !=''THEN ' DEFAULT '||d.adsrc ELSE '' END
      AS sql
    FROM pg_attribute f
        JOIN pg_class c ON c.oid = f.attrelid
        LEFT JOIN pg_attrdef d ON d.adrelid = c.oid AND d.adnum = f.attnum
    WHERE c.relkind = 'r'::char
        AND f.attnum > 0
    ORDER BY f.attnum
  )  UNION (
    SELECT -- CONSTRAINTS
        c.oid as id
        ,c.relname as table
        ,0 as prio
        ,CASE
          WHEN p.contype = 'p' THEN 'PRIMARY KEY'
          WHEN p.contype = 'u' THEN 'UNIQ'
          ELSE '' END
        ||'('||array_to_string(array_agg(f.attname),', ')||')' AS sql
    FROM pg_attribute f
        JOIN pg_class c ON c.oid = f.attrelid
        LEFT JOIN pg_constraint p ON p.conrelid = c.oid AND f.attnum = ANY (p.conkey)
    WHERE c.relkind = 'r'::char
        AND f.attnum > 0
        AND p.contype IN ('u','p')
    GROUP BY c.oid,p.contype,f.attrelid,c.relname
    ORDER BY c.oid,f.attrelid
  )
ORDER BY prio DESC) sql
GROUP BY sql.id,sql.table
;

If you want to copy or clone packages from one Debian or Ubuntu server to another, here is how to to it:

ssh server1 ssh server2 ‘dpkg –get-selections’| dpkg –set-selections apt-get -u dselect-upgrade

• Redirect video with VLC:

  raspivid -o – -t 99999 -hf -w 400 -h 300 -fps 25|sudo -u nico — cvlc -v – –noaudio –no-sout-audio –sout ‘#standard{access=http,mux=ts,dst=:8090}’ :demux=h264

• Redirect video with netcat:

  while true; do raspivid -w 640 -h 480 -fps 25 -t 99999 -o – | nc -l -p 5001; sleep 1 ; done

Test your disk speed:

fio –randrepeat=1 –ioengine=libaio –direct=1 –gtod_reduce=1 –name=test –filename=test –bs=4k –iodepth=64 –size=4G –readwrite=randrw –rwmixread=75

hdparm -tT /dev/root

$> telnet localhost smtp

Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
220 mailtest ESMTP Postfix (Debian/GNU)

$> ehlo example.com

250-my-new-mailserver
250-PIPELINING
250-SIZE 10240000
250-VRFY
250-ETRN
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN

$> mail from:<nico@example.com>

250 2.1.0 Ok

$> rcpt to:<admin@example.com>

250 2.1.5 Ok

$> data

354 End data with <CR><LF>.<CR><LF>

$> Hi Admin,
$> 
$> What's up ?
$> .

250 2.0.0 Ok: queued as A9D64379C4

$> quit

Few tips about fail2ban:

• How to delete or free a blocked ip: fail2ban-client get jail actionunban ipaddress

Anoying things about ruby:

1. i++ does not work!
2. backward version compatibility
3. Regexp not as powerfull than perl
4. Handling types