--- unixtoolbox.xhtml   28 Feb 2008 23:41:29 -0000   1.11
+++ unixtoolbox.xhtml   9 Apr 2008 19:36:05 -0000   1.22
@@ -10,7 +10,7 @@
   <meta name="copyright" content="Copyright © 2007-2008 Colin Barschel. Some rights reserved under Creative Commons [Attribution - Share Alike]" />
   <meta name="description" content="A collection of Unix/Linux/BSD commands and tasks which are useful for IT work or for advanced users, a compact and practical reference." />
   <meta name="abstract" content="Unix Toolbox a compact and practical reference for sysadmins and advanced users." />
-  <meta name="subject" content="Unix Toolbox revision 11" />
+  <meta name="subject" content="Unix Toolbox revision 12" />
   <meta name="keywords" content="Unix Toolbox, Unix tools, Unix, FreeBSD, Linux, commands list, sysadmin, practical guide, advanced reference, common Linux tasks, syntax reminder, howtos, ssh tunnels, rsync, ssl certificates" />
   <style type="text/css" >
 /* basic CSS common to all media */
@@ -112,7 +112,7 @@
     ol.toc, ol.toc li  {
         margin: 0;
         list-style-type: none;
-        padding: 0.27em 0;
+        padding: 0.13em 0;
         text-indent: 0;
         text-align: left;
     }
@@ -126,9 +126,10 @@
 }
 
 @media print {
+/* layout */
 /* Menu as TOC for print */
     body {
-        font-size: 89%;
+        font-size: 88%;
     }   
     div.title {
         padding: 0.5em 0 2em 0;
@@ -238,7 +239,7 @@
         padding: 0 0 5mm 0;
         content: counter(page);
         font-family: verdana, sans-serif;
-        font-size: 89%;
+        font-size: 88%;
     }
     @top {
         padding-top: 5mm;
@@ -288,6 +289,16 @@
     color:#0000FF;
 }
 }
+@media print {
+/* print only colors */
+pre, code { 
+    color: #000;
+}
+a:link, a:visited, .cmt {
+    background-color: transparent;
+    color: #000060;
+}
+}
 </style>
 <style type="text/css" title="inverse" >
 @media screen, handheld {
@@ -386,8 +397,8 @@
 This document is a collection of Unix/Linux/BSD commands and tasks which are useful for IT work or for advanced users. This is a practical guide with concise explanations, however the reader is supposed to know what s/he is doing.<br /><br />
 </div>
 <div class="footerfirst">
-Unix Toolbox revision 11<br />
-The latest version of this document can be found at <a href="http://cb.vu/unixtoolbox.xhtml">http://cb.vu/unixtoolbox.xhtml</a>. Replace .xhtml on the link with <a href="http://cb.vu/unixtoolbox.pdf">.pdf</a> for the PDF version and with <a href="http://cb.vu/unixtoolbox.book.pdf">.book.pdf</a> for the booklet version. On a duplex printer the booklet will create a small book ready to bind. <span class="web">This XHTML page can be converted into a nice PDF document with a CSS3 compliant application (see the <a class="xref" href="#bourneexample">script example</a>).</span><br />
+Unix Toolbox revision 12<br />
+The latest version of this document can be found at <a href="http://cb.vu/unixtoolbox.xhtml">http://cb.vu/unixtoolbox.xhtml</a>. Replace .xhtml on the link with <a href="http://cb.vu/unixtoolbox.pdf">.pdf</a> for the PDF version and with <a href="http://cb.vu/unixtoolbox.book.pdf">.book.pdf</a> for the booklet version. On a duplex printer the booklet will create a small book ready to bind. <span class="web">This XHTML page can be converted into a nice PDF document with a CSS3 compliant application (see the <a class="xref" href="#bourneexample">script example</a>).</span> See also the <a href="http://cb.vu/unixtoolbox">about page</a>.<br />
 Error reports and comments are most welcome - <a href="mailto:c\at\cb.vu">c@cb.vu</a> Colin Barschel.
 <p class="copyright">&#169; <a href="mailto:c_at_cb.vu">Colin Barschel</a> 2007-2008. <a rel="license" href="http://creativecommons.org/licenses/by-sa/3.0/">Some rights reserved under Creative Commons</a>.
 </p>
@@ -445,6 +456,7 @@
 <p class="xrefp"><a class="xrefp" href="#hardwareinfo">Hardware</a> | <a class="xrefp" href="#loadstats">Statistics</a> | <a class="xrefp" href="#users">Users</a> | <a class="xrefp" href="#limits">Limits</a> | <a class="xrefp" href="#runlevels">Runlevels</a> | <a class="xrefp" href="#resetpasswd">root password</a> | <a class="xrefp" href="#compilekernel">Compile kernel</a></p>
 Running kernel and system information
 <pre># uname -a                           <span class="cmt"># Get the kernel version (and BSD version)</span>
+# lsb_release -a                     <span class="cmt"># Full release info of any LSB distribution</span>
 # cat /etc/SuSE-release              <span class="cmt"># Get SuSE version</span>
 # cat /etc/debian_version            <span class="cmt"># Get Debian version</span>
 </pre>
@@ -513,7 +525,7 @@
 # pw userdel colin; pw groupdel admin
 </pre>
 Encrypted passwords are stored in /etc/shadow for Linux and Solaris and /etc/master.passwd on FreeBSD. If the master.passwd is modified manually (say to delete a password), run <code># pwd_mkdb -p master.passwd</code> to rebuild the database.<br /><br />
-To temporarily prevent logins system wide (for all users but root) use nologin. The message in nologin will be displayed.
+To temporarily prevent logins system wide (for all users but root) use nologin. The message in nologin will be displayed (might not work with ssh pre-shared keys).
 <pre># echo "Sorry no login now" > /etc/nologin       <span class="cmt"># (Linux)</span>
 # echo "Sorry no login now" > /var/run/nologin   <span class="cmt"># (FreeBSD)</span>
 </pre>
@@ -541,6 +553,7 @@
 <pre># sysctl -a                          <span class="cmt"># View all system limits</span>
 # sysctl fs.file-max                 <span class="cmt"># View max open files limit</span>
 # sysctl fs.file-max=102400          <span class="cmt"># Change max open files limit</span>
+# echo "1024 50000" > /proc/sys/net/ipv4/ip_local_port_range  <span class="cmt"># port range</span>
 # cat /etc/sysctl.conf
 fs.file-max=102400                   <span class="cmt"># Permanent entry in sysctl.conf</span>
 # cat /proc/sys/fs/file-nr           <span class="cmt"># How many file descriptors are in use</span>
@@ -561,6 +574,7 @@
 kern.ipc.somaxconn=8192              <span class="cmt"># TCP queue. Better for apache/sendmail</span>
 # sysctl kern.openfiles              <span class="cmt"># How many file descriptors are in use</span>
 # sysctl kern.ipc.numopensockets     <span class="cmt"># How many open sockets are in use</span>
+# sysctl -w net.inet.ip.portrange.last=50000 <span class="cmt"># Default is 1024-5000</span>
 </pre>
 See The <a href="http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/configtuning-kernel-limits.html">FreeBSD handbook Chapter 11</a><span class="fn">http://www.freebsd.org/handbook/configtuning-kernel-limits.html</span> for details.
 
@@ -630,9 +644,15 @@
 # sync; mount -o remount,ro /        <span class="cmt"># sync before to remount read only</span>
 # reboot
 </pre> 
+<h3>FreeBSD method 1</h3>
+On FreeBSD, boot in single user mode, remount / rw and use passwd. You can select the single user mode on the boot menu (option 4) which is displayed for 10 seconds at startup. The single user mode will give you a root shell on the / partition.
+<pre># mount -u /; mount -a               <span class="cmt"># will mount / rw</span>
+# passwd
+# reboot
+</pre>
 
-<h3>FreeBSD and Linux method 2</h3>
-FreeBSD won't let you go away with the simple init trick. The solution is to mount the root partition from an other OS (like a rescue CD) and change the password on the disk.
+<h3>Unixes and FreeBSD and Linux method 2</h3>
+Other Unixes might not let you go away with the simple init trick. The solution is to mount the root partition from an other OS (like a rescue CD) and change the password on the disk.
 <ul>
   <li>Boot a live CD or installation CD into a rescue mode which will give you a shell.</li>
   <li>Find the root partition with fdisk e.g. fdisk /dev/sda</li>
@@ -643,11 +663,7 @@
 # passwd
 # reboot
 </pre>
-Alternatively on FreeBSD, boot in single user mode, remount / rw and use passwd.
-<pre># mount -u /; mount -a               <span class="cmt"># will mount / rw</span>
-# passwd
-# reboot
-</pre>
+
 
 <h2 id="kernelmodules">Kernel modules</h2>
 <h3>Linux</h3>
@@ -662,7 +678,7 @@
 <h3>Linux</h3>
 <pre># cd /usr/src/linux
 # make mrproper                      <span class="cmt"># Clean everything, including config files</span>
-# make oldconfig                     <span class="cmt"># Create a new config file from the current kernel</span>
+# make oldconfig                     <span class="cmt"># Reuse the old .config if existent</span>
 # make menuconfig                    <span class="cmt"># or xconfig (Qt) or gconfig (GTK)</span>
 # make                               <span class="cmt"># Create a compressed kernel image</span>
 # make modules                       <span class="cmt"># Compile the modules</span>
@@ -689,7 +705,7 @@
 # reboot
 </pre>
 For small changes in the source, sometimes the short version is enough:
-<pre># make kernel world                  <span class="cmt"># Compile and install both kernel and OS</span>
+<pre># make kernel world                  <span class="cmt"># Compile/install all (for the brave only)</span>
 # mergemaster
 # reboot
 </pre>
@@ -703,8 +719,10 @@
 However more typical usage is with a pipe or with <code>pgrep</code>:
 <pre># ps axww | grep cron
   586  ??  Is     0:01.48 /usr/sbin/cron -s
+# ps aux | grep 'ss[h]'              <span class="cmt"># Find all ssh pids without the grep pid</span>
 # pgrep -l sshd                      <span class="cmt"># Find the PIDs of processes by (part of) name</span>
-# fuser -va 22/tcp                   <span class="cmt"># List processes using port 22</span>
+# echo $$                            <span class="cmt"># The PID of your shell</span>
+# fuser -va 22/tcp                   <span class="cmt"># List processes using port 22 (Linux)</span>
 # fuser -va /home                    <span class="cmt"># List processes accessing the /home partiton</span>
 # strace df                          <span class="cmt"># Trace system calls and signals</span>
 # truss df                           <span class="cmt"># same as above on FreeBSD/Solaris/Unixware</span>
@@ -721,6 +739,12 @@
 # nice -n 5 top                      <span class="cmt"># Weaker priority (/usr/bin/nice)</span>
 # nice +5 top                        <span class="cmt"># tcsh builtin nice (same as above!)</span>
 </pre>
+While nice changes the CPU scheduler, an other useful command <code>ionice</code> will schedule the disk IO. This is very useful for intensive IO application which can bring a machine to its knees while still in a lower priority. The command is only available on Linux (AFAIK). You can select a class (idle - best effort - real time), the man page is short and well explained.
+<pre># ionice c3 -p123                    <span class="cmt"># set idle class for pid 123</span>
+# ionice -c2 -n0 firefox             <span class="cmt"># Run firefox with best effort and high priority</span>
+# ionice -c3 -p$$                    <span class="cmt"># Set the actual shell to idle priority</span>
+</pre>
+For example last command is very useful to compile (or debug) a large project. Every command launched from this shell will have a lover priority and will not disturb the system. $$ is your shell pid (try echo $$).
 
 <h2 id="bgfg">Background/Foreground</h2>
 When started from a shell, processes can be brought in the background and back to the foreground with [Ctrl]-[Z] (^Z), <code>bg</code> and <code>fg</code>. For example start two processes, bring them in the background, list the processes with <code>jobs</code> and bring one in the foreground.
@@ -737,7 +761,7 @@
 </pre>
 
 <h2 id="top">Top</h2>
-The program <code>top</code> displays running information of processes.
+The program <code>top</code> displays running information of processes. The program <code>htop</code> from htop.sourceforge.net is a very nice alternative and a more powerful version of top. Runs on Linux and FreeBSD (<code>ports/sysutils/htop/</code>).
 <pre># top</pre>
 While top is running press the key h for a help overview. Useful keys are:
 <ul>
@@ -770,7 +794,7 @@
 <div id="filesystem"><h1><a>File System</a></h1>
 <p class="xrefp"><a class="xrefp" href="#diskinfo">Disk info</a> | <a class="xrefp" href="#fsboot">Boot</a> | <a class="xrefp" href="#mountpoints">Disk usage</a> | <a class="xrefp" href="#filesstat">Opened files</a> | <a class="xrefp" href="#mountcd">Mount/remount</a> | <a class="xrefp" href="#mountsmb">Mount SMB</a> | <a class="xrefp" href="#mountimg">Mount image</a> | <a class="xrefp" href="#burniso">Burn ISO</a> | <a class="xrefp" href="#createimg">Create image</a> | <a class="xrefp" href="#creatememdisk">Memory disk</a> | <a class="xrefp" href="#diskperf">Disk performance</a></p>
 <h2 id="permissions">Permissions</h2>
-Change permission and ownership with <code>chmod</code> and <code>chown</code>. The default umask can be changed for all users in /etc/profile for Linux or /etc/login.conf for FreeBSD. The default umask is usually 022. The umsak is subtracted from 777, thus umask 022 results in a permission 0f 755.
+Change permission and ownership with <code>chmod</code> and <code>chown</code>. The default umask can be changed for all users in /etc/profile for Linux or /etc/login.conf for FreeBSD. The default umask is usually 022. The umask is subtracted from 777, thus umask 022 results in a permission 0f 755.
 <pre>1 --x execute                        <span class="cmt"># Mode 764 = exec/read/write | read/write | read</span>
 2 -w- write                          <span class="cmt"># For:       |--  Owner  --|   |- Group-|   |Oth|</span>
 4 r-- read
@@ -784,6 +808,8 @@
 # find / -perm -u+s -print           <span class="cmt"># Find all programs with the SUID bit</span>
 # chown user:group /path/to/file     <span class="cmt"># Change the user and group ownership of a file</span>
 # chgrp group /path/to/file          <span class="cmt"># Change the group ownership of a file</span>
+# chmod 640 `find ./ -type f -print` <span class="cmt"># Change permissions to 640 for all files</span>
+# chmod 751 `find ./ -type d -print` <span class="cmt"># Change permissions to 751 for all directories</span>
 </pre>
 <h2 id="diskinfo">Disk information</h2>
 <pre># diskinfo -v /dev/ad2               <span class="cmt"># information about disk (sector/size) FreeBSD</span>
@@ -880,7 +906,8 @@
 <h3>Linux</h3>
 <pre># mount -t auto /dev/cdrom /mnt/cdrom   <span class="cmt"># typical cdrom mount command</span>
 # mount /dev/hdc -t iso9660 -r /cdrom   <span class="cmt"># typical IDE</span>
-# mount /dev/sdc0 -t iso9660 -r /cdrom  <span class="cmt"># typical SCSI</span>
+# mount /dev/scd0 -t iso9660 -r /cdrom  <span class="cmt"># typical SCSI cdrom</span>
+# mount /dev/sdc0 -t ntfs-3g /windows   <span class="cmt"># typical SCSI</span>
 </pre>
 Entry in /etc/fstab:
 <pre>/dev/cdrom   /media/cdrom  subfs noauto,fs=cdfss,ro,procuid,nosuid,nodev,exec 0 0</pre>
@@ -899,6 +926,15 @@
 Copy the raw data from a cdrom into an iso image:
 <pre># dd if=/dev/cd0c of=file.iso</pre>
 
+<h2 id="addswap">Add swap on-the-fly</h2>
+Suppose you need more swap (right now), say a 2GB file /swap2gb (Linux only).
+<pre># dd if=/dev/zero of=/swap2gb bs=1024k count=2000
+# mkswap /swap2gb                    <span class="cmt"># create the swap area</span>
+# swapon /swap2gb                    <span class="cmt"># activate the swap. It now in use</span>
+# swapoff /swap2gb                   <span class="cmt"># when done deactivate the swap</span>
+# rm /swap2gb
+</pre>
+
 <h2 id="mountsmb">Mount an SMB share</h2>
 Suppose we want to access the SMB share myshare on the computer smbserver, the address as typed on a Windows PC is \\smbserver\myshare\. We mount on /mnt/smbshare. Warning> cifs wants an IP or DNS name, not a Windows name.
 <h3>Linux</h3>
@@ -963,6 +999,13 @@
 Also use <code>cdrecord</code> with Linux as described above. Additionally it is possible to use the native ATAPI interface which is found with:
 <pre># cdrecord dev=ATAPI -scanbus</pre>
 And burn the CD/DVD as above.
+<h4>dvd+rw-tools</h4>
+The <a href="http://fy.chalmers.se/~appro/linux/DVD+RW/">dvd+rw-tools</a> package (FreeBSD: ports/sysutils/dvd+rw-tools) can do it all and includes <code>growisofs</code> to burn CDs or DVDs. The examples refere to the dvd device as <code>/dev/dvd</code> which could be a symlink to <code>/dev/scd0</code> (typical scsi on Linux) or <code>/dev/cd0</code> (typical FreeBSD) or <code>/dev/rcd0c</code> (typical NetBSD/OpenBSD character SCSI) or <code>/dev/rdsk/c0t1d0s2</code> (Solaris example of a character SCSI/ATAPI CD-ROM device). There is a nice documentation with examples on the <a href="http://www.freebsd.org/handbook/creating-dvds.html">FreeBSD handbook chapter 18.7</a><span class="fn">http://www.freebsd.org/handbook/creating-dvds.html</span>.
+<pre>                       <span class="cmt"># -dvd-compat closes the disk</span>
+# growisofs -dvd-compat -Z /dev/dvd=imagefile.iso     <span class="cmt"># Burn existing iso image</span>
+# growisofs -dvd-compat -Z /dev/dvd -J -R /p/to/data  <span class="cmt"># Burn directly</span>
+</pre>
+
 <h3>Convert a Nero .nrg file to .iso</h3>
 Nero simply adds a 300Kb header to a normal iso image. This can be trimmed with dd.
 <pre># dd bs=1k if=imagefile.nrg of=imagefile.iso skip=300</pre>
@@ -972,15 +1015,31 @@
 </pre>
 
 <h2 id="createimg">Create a file based image</h2>
-For example a partition of 1GB using the file /usr/vdisk.img.
+For example a partition of 1GB using the file /usr/vdisk.img. Here we use the vnode 0, but it could also be 1.
 <h3>FreeBSD</h3>
 <pre># dd if=/dev/random of=/usr/vdisk.img bs=1K count=1M
-# mdconfig -a -t vnode -f /usr/vdisk.img -u 1         <span class="cmt"># Creates device /dev/md1</span>
-# bsdlabel -w /dev/md1
-# newfs /dev/md1c
-# mount /dev/md1c /mnt
-# umount /mnt; mdconfig -d -u 1; rm /usr/vdisk.img    <span class="cmt"># Cleanup the md device</span>
+# mdconfig -a -t vnode -f /usr/vdisk.img -u 0         <span class="cmt"># Creates device /dev/md1</span>
+# bsdlabel -w /dev/md0
+# newfs /dev/md0c
+# mount /dev/md0c /mnt
+# umount /mnt; mdconfig -d -u 0; rm /usr/vdisk.img    <span class="cmt"># Cleanup the md device</span>
+</pre>
+The file based image can be automatically mounted during boot with an entry in /etc/rc.conf and /etc/fstab. Test your setup with <code># /etc/rc.d/mdconfig start</code> (first delete the md0 device with <code># mdconfig -d -u 0</code>).<br />
+Note however that this automatic setup will only work if the file image is NOT on the root partition. The reason is that the /etc/rc.d/mdconfig script is executed very early buring boot and the root partition is still read-only. Images located outside the root partition will be mounted later with the script /etc/rc.d/mdconfig2.<br />
+/boot/loader.conf:
+<pre>md_load="YES"</pre>
+/etc/rc.conf:
+<pre># mdconfig_md0="-t vnode -f /usr/vdisk.img"          <span class="cmt"># /usr is not on the root partition</span></pre>
+/etc/fstab: (The 0 0 at the end is important, it tell fsck to ignore this device, as is does not exist yet)
+<pre>/dev/md0                /usr/vdisk      ufs     rw              0       0</pre>
+It is also possible to increase the size of the image afterward, say for example 300 MB larger.
+<pre># umount /mnt; mdconfig -d -u 0
+# dd if=/dev/zero bs=1m count=300 >> /usr/vdisk.img
+# mdconfig -a -t vnode -f /usr/vdisk.img -u 0
+# growfs /dev/md0
+# mount /dev/md0c /mnt                                <span class="cmt"># File partition is now 300 MB larger</span>
 </pre>
+
 <h3>Linux</h3>
 
 <pre># dd if=/dev/zero of=/usr/vdisk.img bs=1024k count=1024
@@ -1022,21 +1081,34 @@
 <div id="network"><h1><a>Network</a></h1>
 <p class="xrefp"><a class="xrefp" href="#routing">Routing</a> | <a class="xrefp" href="#secondip">Additional IP</a> | <a class="xrefp" href="#changemac">Change MAC</a> | <a class="xrefp" href="#ports">Ports</a> | <a class="xrefp" href="#firewall">Firewall</a> | <a class="xrefp" href="#ipforward">IP Forward</a> | <a class="xrefp" href="#nat">NAT</a> | <a class="xrefp" href="#dns">DNS</a> | <a class="xrefp" href="#dhcp">DHCP</a> | <a class="xrefp" href="#traffic">Traffic</a> | <a class="xrefp" href="#trafficctrl">QoS</a> | <a class="xrefp" href="#nis">NIS</a></p>
 <h2 id="netdebug">Debugging (See also <a class="xref" href="#traffic">Traffic analysis)</a></h2>
-<pre># mii-diag eth0             <span class="cmt"># Show the link status (Linux)</span>
-# ifconfig fxp0             <span class="cmt"># Check the "media" field on FreeBSD</span>
+<h3>Linux</h3>
+<pre># ethtool eth0              <span class="cmt"># Show the ethernet status (replaces mii-diag)</span>
+# ethtool -s eth0 speed 100 duplex full <span class="cmt"># Force 100Mbit Full duplex</span>
+# ethtool -s eth0 autoneg off <span class="cmt"># Disable auto negotiation</span>
+# ethtool -p eth1           <span class="cmt"># Blink the ethernet led - very useful when supported</span>
+# ip link show              <span class="cmt"># Display all interfaces on Linux (similar to ifconfig)</span>
+# ip link set eth0 up       <span class="cmt"># Bring device up (or down). Same as "ifconfig eth0 up"</span>
+# ip addr show              <span class="cmt"># Display all IP addresses on Linux (similar to ifconfig)</span>
+# ip neigh show             <span class="cmt"># Similar to arp -a</span>
+</pre>
+<h3>Other OSes</h3>
+<pre># ifconfig fxp0             <span class="cmt"># Check the "media" field on FreeBSD</span>
 # arp -a                    <span class="cmt"># Check the router (or host) ARP entry (all OS)</span>
 # ping cb.vu                <span class="cmt"># The first thing to try...</span>
 # traceroute cb.vu          <span class="cmt"># Print the route path to destination</span>
-# mii-diag -F 100baseTx-FD eth0  <span class="cmt"># Force 100Mbit Full duplex (Linux)</span>
-# ifconfig fxp0 media 100baseTX mediaopt full-duplex  <span class="cmt"># Same for FreeBSD</span>
+# ifconfig fxp0 media 100baseTX mediaopt full-duplex <span class="cmt"># 100Mbit full duplex (FreeBSD)</span>
 # netstat -s                <span class="cmt"># System-wide statistics for each network protocol</span>
 </pre>
+Additional commands which are not always installed per default but easy to find:
+<pre># arping 192.168.16.254     <span class="cmt"># Ping on ethernet layer</span>
+# tcptraceroute -f 5 cb.vu  <span class="cmt"># uses tcp instead of icmp to trace throught firewalls</span>
+</pre>
 
 <h2 id="routing">Routing</h2>
 <h3>Print routing table</h3>
-<pre># route -n                 <span class="cmt"># Linux</span>
-# netstat -rn              <span class="cmt"># Linux, BSD and UNIX</span>
-# route print              <span class="cmt"># Windows</span>
+<pre># route -n                  <span class="cmt"># Linux or use "ip route"</span>
+# netstat -rn               <span class="cmt"># Linux, BSD and UNIX</span>
+# route print               <span class="cmt"># Windows</span>
 </pre>
 <h3 id="addroute">Add and delete a route</h3>
 <h4>FreeBSD</h4>
@@ -1053,9 +1125,15 @@
 # ip route add 192.168.20.0/24 via 192.168.16.254       <span class="cmt"># same as above with ip route</span>
 # route add -net 192.168.20.0 netmask 255.255.255.0 dev eth0
 # route add default gw 192.168.51.254
-# ip route add default via 192.168.51.254               <span class="cmt"># same as above with ip route</span>
+# ip route add default via 192.168.51.254 dev eth0      <span class="cmt"># same as above with ip route</span>
 # route delete -net 192.168.20.0 netmask 255.255.255.0
 </pre>
+<h4>Solaris</h4>
+<pre># route add -net 192.168.20.0 -netmask 255.255.255.0 192.168.16.254
+# route add default 192.168.51.254 1                    <span class="cmt"># 1 = hops to the next gateway</span>
+# route change default 192.168.50.254 1
+</pre>
+Permanent entries are set in entry in <code>/etc/defaultrouter</code>.
 <h4>Windows</h4>
 <pre># Route add 192.168.50.0 mask 255.255.255.0 192.168.51.253
 # Route add 0.0.0.0 mask 0.0.0.0 192.168.51.254</pre>
@@ -1065,6 +1143,8 @@
 <h3>Linux</h3>
 <pre># ifconfig eth0 192.168.50.254 netmask 255.255.255.0       <span class="cmt"># First IP</span>
 # ifconfig eth0:0 192.168.51.254 netmask 255.255.255.0     <span class="cmt"># Second IP</span>
+# ip addr add 192.168.50.254/24 dev eth0                   <span class="cmt"># Equivalent ip commands</span>
+# ip addr add 192.168.51.254/24 dev eth0 label eth0:1
 </pre>
 <h3>FreeBSD</h3>
 <pre># ifconfig fxp0 inet 192.168.50.254/24                     <span class="cmt"># First IP</span>
@@ -1073,10 +1153,23 @@
 <pre>ifconfig_fxp0="inet 192.168.50.254  netmask 255.255.255.0"
 ifconfig_fxp0_alias0="192.168.51.254 netmask 255.255.255.0"
 </pre>
+<h3>Solaris</h3>
+Check the settings with <code>ifconfig -a</code>
+<pre># ifconfig hme0 plumb                                      <span class="cmt"># Enable the network card</span>
+# ifconfig hme0 192.168.50.254 netmask 255.255.255.0 up    <span class="cmt"># First IP</span>
+# ifconfig hme0:1 192.168.51.254 netmask 255.255.255.0 up  <span class="cmt"># Second IP</span>
+</pre>
+
 <h2 id="changemac">Change MAC address</h2>
-<pre># ifconfig eth0 hw ether 00:01:02:03:04:05      <span class="cmt"># Linux</span>
+Normally you have to bring the interface down before the change. Don't tell me why you want to change the MAC address...
+<pre># ifconfig eth0 down
+# ifconfig eth0 hw ether 00:01:02:03:04:05      <span class="cmt"># Linux</span>
 # ifconfig fxp0 link 00:01:02:03:04:05          <span class="cmt"># FreeBSD</span>
+# ifconfig hme0 ether 00:01:02:03:04:05         <span class="cmt"># Solaris</span>
+# sudo ifconfig en0 ether 00:01:02:03:04:05     <span class="cmt"># Mac OS X Tiger</span>
+# sudo ifconfig en0 lladdr 00:01:02:03:04:05    <span class="cmt"># Mac OS X Leopard</span>
 </pre>
+Many tools exist for Windows. For example <a href="http://ntsecurity.nu/toolbox/etherchange/">etherchange</a><span class="fn">http://ntsecurity.nu/toolbox/etherchange</span>. Or look for "Mac Makeup", "smac".
 
 <h2 id="ports">Ports in use</h2>
 Listening open ports:
@@ -1095,12 +1188,12 @@
 <h3>Linux</h3>
 <pre># iptables -L -n -v                  <span class="cmt"># For status</span>
 Open the iptables firewall
-# iptables -Z                        <span class="cmt"># Zero the packet and byte counters in all chains</span>
-# iptables -F                        <span class="cmt"># Flush all chains</span>
-# iptables -X                        <span class="cmt"># Delete all chains</span>
 # iptables -P INPUT       ACCEPT     <span class="cmt"># Open everything</span>
 # iptables -P FORWARD     ACCEPT
 # iptables -P OUTPUT      ACCEPT
+# iptables -Z                        <span class="cmt"># Zero the packet and byte counters in all chains</span>
+# iptables -F                        <span class="cmt"># Flush all chains</span>
+# iptables -X                        <span class="cmt"># Delete all chains</span>
 </pre>
 <h3>FreeBSD</h3>
 <pre># ipfw show                          <span class="cmt"># For status</span>
@@ -1125,6 +1218,11 @@
 Permanent with entry in /etc/rc.conf:
 gateway_enable="YES"                 <span class="cmt"># Set to YES if this host will be a gateway.</span>
 </pre>
+
+<h3>Solaris</h3>
+<pre># ndd -set /dev/ip ip_forwarding 1   <span class="cmt"># Set IP forward 0=off, 1=on</span>
+</pre>
+
 <h2 id="nat">NAT Network Address Translation</h2>
 <h3>Linux</h3>
 <pre># iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE   <span class="cmt"># to activate NAT</span>
@@ -1204,7 +1302,7 @@
 <h2 id="dhcp">DHCP</h2>
 <h3>Linux</h3>
 Some distributions (SuSE) use dhcpcd as client. The default interface is eth0.
-<pre># dhcpcd -n eth0           <span class="cmt"># Trigger a renew</span>
+<pre># dhcpcd -n eth0           <span class="cmt"># Trigger a renew (does not always work)</span>
 # dhcpcd -k eth0           <span class="cmt"># release and shutdown</span>
 </pre>
 The lease with the full information is stored in:
@@ -1268,6 +1366,7 @@
 Running: FreeBSD 5.X
 Uptime 33.120 days (since Fri Aug 31 11:41:04 2007)
 </pre>
+Other non standard but useful tools are <code>hping</code> (www.hping.org) an IP packet assembler/analyzer and <code>fping</code> (fping.sourceforge.net). fping can check multiple hosts in a round-robin fashion.
 
 <h2 id="trafficctrl">Traffic control (QoS)</h2>
 Traffic control manages the queuing, policing, scheduling, and other traffic parameters for a network. The following examples are simple practical uses of the Linux and FreeBSD capabilities to better use the available bandwidth.
@@ -1651,19 +1750,20 @@
 </div>
 
 <div id="crypt"><h1><a>Encrypt Files</a></h1>
-<h2>A single file</h2>
+<h2>OpenSSL</h2>
+<h3>A single file</h3>
 Encrypt and decrypt:
 <pre># openssl des -salt -in file -out file.des
 # openssl des -d -salt -in file.des -out file
 </pre>
 Note that the file can of course be a tar archive.
     
-<h2>tar and encrypt a whole directory</h2>
+<h3>tar and encrypt a whole directory</h3>
 <pre># tar -cf - directory | openssl des -salt -out directory.tar.des      <span class="cmt"># Encrypt</span>
 # openssl des -d -salt -in directory.tar.des | tar -x                 <span class="cmt"># Decrypt</span>
 </pre>
     
-<h2>tar zip and encrypt a whole directory</h2>
+<h3>tar zip and encrypt a whole directory</h3>
 <pre># tar -zcf - directory | openssl des -salt -out directory.tar.gz.des  <span class="cmt"># Encrypt</span>
 # openssl des -d -salt -in directory.tar.gz.des | tar -xz             <span class="cmt"># Decrypt</span>
 </pre>
@@ -1672,6 +1772,65 @@
 <li>Use -k mysecretpassword after des to avoid the interactive password request. However note that this is highly insecure.</li>
 <li>Use <strong>des3</strong> instead of <strong>des</strong> to get even stronger encryption (Triple-DES Cipher). This uses also more CPU.</li>
 </ul>
+
+<h2>GPG</h2>
+<a href="http://gnupg.org/">GnuPG</a> is well known to encrypt and sign emails or any data. Furthermore gpg and also provides an advanced key management system. This section only covers files encryption, not email usage, signing or the Web-Of-Trust.<br />
+The simplest encryption is with a symmetric cipher. In this case the file is encrypted with a password and anyone who knows the password can decrypt it, thus the keys are not needed. Gpg adds an extention ".gpg" to the encrypted file names.
+<pre># gpg -c file                        <span class="cmt"># Encrypt file with password</span>
+# gpg file.gpg                       <span class="cmt"># Decrypt file (optionally -o otherfile)</span>
+</pre>
+<h3>Using keys</h3>
+For more details see <a href="http://www.madboa.com/geek/gpg-quickstart">GPG Quick Start</a><span class="fn">http://www.madboa.com/geek/gpg-quickstart</span> and <a href="http://aplawrence.com/Basics/gpg.html">GPG/PGP Basics</a><span class="fn">http://aplawrence.com/Basics/gpg.html</span> and the <a href="http://gnupg.org/documentation">gnupg documentation</a><span class="fn">http://gnupg.org/documentation</span> among others.<br />
+The private and public keys are the heart of asymmetric cryptography. What is important to remember:
+<ul>
+<li>Your public key is used by <i>others</i> to encrypt files that only you as the receiver can decrypt (not even the one who encrypted the file can decrypt it). The public key is thus meant to be distributed.</li>
+<li>Your private key is encrypted with your passphrase and is used to decrypt files which where encrypted with <i>your</i> public key. The private key must be kept <b>secure</b>. Also if the key or passphrase is lost, so are all the files encrypted with your public key.</li>
+<li>The key files are called keyrings as they can contain more than one key.</li>
+</ul>
+First generate a key pair. The defaults are fine, however you will have to enter at least your full name and email and optionally a comment. The comment is useful to create more than one key with the same name and email. Also you should use a "passphrase", not a simple password.
+<pre># gpg --gen-key                      <span class="cmt"># This can take a long time</span></pre>
+The keys are stored in ~/.gnupg/ on Unix, on Windows they are typically stored in<br />
+C:/Documents and Settings/%USERNAME%/Application Data/gnupg/.
+<pre>~/.gnupg/pubring.gpg                 <span class="cmt"># Contains your public keys and all others imported</span>
+~/.gnupg/secring.gpg                 <span class="cmt"># Can contain more than one private key</span>
+</pre>
+Short reminder on most used options:
+<ul style="list-style-type:none; page-break-inside:avoid;">
+  <li><b>-e</b> encrypt data</li>
+  <li><b>-d</b> decrypt data</li>
+  <li><b>-r</b> NAME encrypt for recipient NAME (or 'Full Name' or 'email@domain')</li>
+  <li><b>-a</b> create ascii armored output of a key</li>
+  <li><b>-o</b> use as output file</li>
+</ul>
+The examples use 'Your Name' and 'Alice' as the keys are referred to by the email or full name or partial name. For example I can use 'Colin' or 'c@cb.vu' for my key [Colin Barschel (cb.vu) &lt;c@cb.vu&gt;].
+<h3>Encrypt for personal use only</h3>
+No need to export/import any key for this. You have both already.
+<pre># gpg -e -r 'Your Name' file                  <span class="cmt"># Encrypt with your public key</span>
+# gpg -o file -d file.gpg                     <span class="cmt"># Decrypt. Use -o or it goes to stdout</span>
+</pre>
+<h3>Encrypt - Decrypt with keys</h3>
+First you need to export your public key for someone else to use it. And you need to import the public say from Alice to encrypt a file for her. You can either handle the keys in simple ascii files or use a public key server.<br />
+For example Alice export her public key and you import it, you can then encrypt a file for her. That is only Alice will be able to decrypt it.
+<pre># gpg -a -o alicekey.asc --export 'Alice'     <span class="cmt"># Alice exported her key in ascii file.</span>
+# gpg --send-keys --keyserver subkeys.pgp.net KEYID   <span class="cmt"># Alice put her key on a server.</span>
+# gpg --import alicekey.asc                   <span class="cmt"># You import her key into your pubring.</span>
+# gpg --search-keys --keyserver subkeys.pgp.net 'Alice' <span class="cmt"># or get her key from a server.</span>
+</pre>
+Once the keys are imported it is very easy to encrypt or decrypt a file:
+<pre># gpg -e -r 'Alice' file                      <span class="cmt"># Encrypt the file for Alice.</span>
+# gpg -d file.gpg -o file                     <span class="cmt"># Decrypt a file encrypted by Alice for you.</span>
+</pre>
+<h3>Key administration</h3>
+<pre># gpg --list-keys                             <span class="cmt"># list public keys and see the KEYIDS</span>
+    <span class="cmt">The KEYID follows the '/' e.g. for: pub   1024D/D12B77CE the KEYID is D12B77CE</span>
+# gpg --gen-revoke 'Your Name'                <span class="cmt"># generate revocation certificate</span>
+# gpg --list-secret-keys                      <span class="cmt"># list private keys</span>
+# gpg --delete-keys NAME                      <span class="cmt"># delete a public key from local key ring</span>
+# gpg --delete-secret-key NAME                <span class="cmt"># delete a secret key from local key ring</span>
+# gpg --fingerprint KEYID                     <span class="cmt"># Show the fingerprint of the key</span>
+# gpg --edit-key KEYID                        <span class="cmt"># Edit key (e.g sign or add/del email)</span>
+</pre>
+
 </div>
 
 <div id="cryptpart"><h1><a>Encrypt Partitions</a></h1>
@@ -1837,6 +1996,7 @@
 To view the certificate information simply do:
 <pre># openssl x509 -text -in servernamecert.pem      <span class="cmt"># View the certificate info</span>
 # openssl req -noout -text -in server.csr        <span class="cmt"># View the request info</span>
+# openssl s_client -connect cb.vu:443            <span class="cmt"># Check a web server certificate</span>
 </pre>
 </div>
 
@@ -2076,7 +2236,8 @@
 
 
 <h2 id="vi">vi</h2>
-Vi is present on ANY Linux/Unix installation and it is therefore useful to know some basic commands. There are two modes: command mode and insertion mode. The commands mode is accessed with <strong>[ESC]</strong>, the insertion mode with <strong>i</strong>.
+Vi is present on ANY Linux/Unix installation (not gentoo?) and it is therefore useful to know some basic commands. There are two modes: command mode and insertion mode. The commands mode is accessed with <strong>[ESC]</strong>, the insertion mode with <strong>i</strong>. Use <code>: help</code> if you are lost.<br />
+The editors <code>nano</code> and <code>pico</code> are usually available too and are easier (IMHO) to use.
 <h3>Quit</h3>
 <ul style="list-style-type: none;">
   <li><strong>:w</strong> newfilename &#160; &#160; &#160; save the file to newfilename</li>
@@ -2148,7 +2309,7 @@
 # tar -czf home.tgz --exclude '*.o' --exclude 'tmp/' home/
 </pre>
 <h2 id="dd">dd</h2>
-The program <code>dd</code> (disk dump) is used to copy partitions and disks and for other copy tricks. Typical usage:
+The program <code>dd</code> (disk dump or destroy disk or see <a href="http://roesler-ac.de/wolfram/acro/credits.htm">the meaning of dd</a>) is used to copy partitions and disks and for other copy tricks. Typical usage:
 <pre># dd if=&lt;source&gt; of=&lt;target&gt; bs=&lt;byte size&gt; conv=&lt;conversion&gt;</pre>
 Important conv options:
 <ul style="list-style-type: none;">
@@ -2182,12 +2343,18 @@
   <span class="cmt"># The above is useful to refresh a disk. It is perfectly safe, but must be unmounted.</span>
 </pre>
 <h3>Delete</h3>
-<pre># dd if=/dev/zero of=/dev/hdc count=1                 <span class="cmt"># Delete MBR and partiton table</span>
-# dd if=/dev/zero of=/dev/hdc                         <span class="cmt"># Delete full disk</span>
+<pre># dd if=/dev/zero of=/dev/hdc                         <span class="cmt"># Delete full disk</span>
 # dd if=/dev/urandom of=/dev/hdc                      <span class="cmt"># Delete full disk better</span>
 # kill -USR1 PID                                      <span class="cmt"># View dd progress (Linux only!)</span>
 </pre>
-
+<h3>MBR tricks</h3>
+The MBR contains the boot loader and the partition table and is 512 bytes small. The first 446 are for the boot loader, the bytes 446 to 512 are for the partition table.
+<pre># dd if=/dev/sda of=/mbr_sda.bak bs=512 count=1       <span class="cmt"># Backup the full MBR</span>
+# dd if=/dev/zero of=/dev/sda bs=512 count=1          <span class="cmt"># Delete MBR and partiton table</span>
+# dd if=/mbr_sda.bak of=/dev/sda bs=512 count=1       <span class="cmt"># Restore the full MBR</span>
+# dd if=/mbr_sda.bak of=/dev/sda bs=446 count=1       <span class="cmt"># Restore only the boot loader</span>
+# dd if=/mbr_sda.bak of=/dev/sda bs=1 count=64 skip=446 seek=446 <span class="cmt"># Restore partition table</span>
+</pre>
 
 <h2 id="screen">screen</h2>
 Screen has two main functionalities:
@@ -2235,20 +2402,23 @@
 # find . -type d ! -perm -111        <span class="cmt"># Find dirs not accessible by all</span>
 # find /home/user/ -cmin 10 -print   <span class="cmt"># Files created or modified in the last 10 min.</span>
 # find . -name '*.[ch]' | xargs grep -E 'expr' <span class="cmt"># Search 'expr' in this dir and below.</span>
-# find / -name "*.core" | xargs rm   <span class="cmt"># Find core dumps and delete them</span>
+# find / -name "*.core" | xargs rm   <span class="cmt"># Find core dumps and delete them (also try core.*)</span>
 # find / -name "*.core" -print -exec rm {} \;  <span class="cmt"># Other syntax</span>
-# find . \( -name "*.png" -o -name "*.jpg" \) -print
-                                     <span class="cmt"># iname is not case sensitive</span>
+      <span class="cmt"># Find images and create an archive, iname is not case sensitive. -r for append</span>
 # find . \( -iname "*.png" -o -iname "*.jpg" \) -print -exec tar -rf images.tar {} \;
 # find . -type f -name "*.txt" ! -name README.txt -print  <span class="cmt"># Exclude README.txt files</span>
-# find /var/ -size +1M -exec ls -lh {} \;
-# find /var/ -size +1M -ls           <span class="cmt"># This is simpler</span>
+# find /var/ -size +10M -exec ls -lh {} \;     <span class="cmt"># Find large files &gt; 10 MB</span>
+# find /var/ -size +10M -ls           <span class="cmt"># This is simpler</span>
 # find . -size +10M -size -50M -print
 # find /usr/ports/ -name work -type d -print -exec rm -rf {} \;  <span class="cmt"># Clean the ports</span>
-    Find files with SUID; those file have to be kept secure
+      <span class="cmt"># Find files with SUID; those file are vulnerable and must be kept secure</span>
 # find / -type f -user root -perm -4000 -exec ls -l {} \; 
 </pre>
-
+Be careful with xarg or exec as it might or might not honor quotings and can return wrong results when files or directories contain spaces. In doubt use "-print0 | xargs -0" instead of "| xargs". The option -print0 must be the last in the find command. See this nice <a href="http://www.hccfl.edu/pollock/Unix/FindCmd.htm">mini tutorial for find</a><span class="fn">http://www.hccfl.edu/pollock/Unix/FindCmd.htm</span>.
+<pre># find . -type f | xargs ls -l       <span class="cmt"># Will not work with spaces in names</span>
+# find . -type f -print0 | xargs -0 ls -l  <span class="cmt"># Will work with spaces in names</span>
+# find . -type f -exec ls -l '{}' \; <span class="cmt"># Or use quotes '{}' with -exec</span>
+</pre>
 <h2 id="misccmd">Miscellaneous</h2>
 <pre># which command                      <span class="cmt"># Show full path name of command</span>
 # time command                       <span class="cmt"># See how long a command takes to execute</span>
@@ -2263,10 +2433,12 @@
 # export varname="value"             <span class="cmt"># set env. variable varname to value (sh/ksh/bash)</span>
 # pwd                                <span class="cmt"># Print working directory</span>
 # mkdir -p /path/to/dir              <span class="cmt"># no error if existing, make parent dirs as needed</span>
+# mkdir -p project/{bin,src,obj,doc/{html,man,pdf},debug/some/more/dirs}
 # rmdir /path/to/dir                 <span class="cmt"># Remove directory</span>
 # rm -rf /path/to/dir                <span class="cmt"># Remove directory and its content (force)</span>
 # cp -la /dir1 /dir2                 <span class="cmt"># Archive and hard link files instead of copy</span>
 # cp -lpR /dir1 /dir2                <span class="cmt"># Same for FreeBSD</span>
+# cp unixtoolbox.xhtml{,.bak}        <span class="cmt"># Short way to copy the file with a new extension</span>
 # mv /dir1 /dir2                     <span class="cmt"># Rename a directory</span>
 </pre>
 </div>
@@ -2288,6 +2460,20 @@
 <pre># apt-get update                     <span class="cmt"># First update the package lists</span>
 # apt-get install emacs              <span class="cmt"># Install the package emacs</span>
 # dpkg --remove emacs                <span class="cmt"># Remove the package emacs</span>
+# dpkg -S file                       <span class="cmt"># find what package a file belongs to</span>
+</pre>
+<h3>Gentoo</h3>
+Gentoo uses emerge as the heart of its "Portage" package management system.
+<pre># emerge --sync                      <span class="cmt"># First sync the local portage tree</span>
+# emerge -u packagename              <span class="cmt"># Install or upgrade a package</span>
+# emerge -C packagename              <span class="cmt"># Remove the package</span>
+# revdep-rebuild                     <span class="cmt"># Repair dependencies</span>
+</pre>
+<h3>Solaris</h3>
+The &lt;cdrom&gt; path is usually <code>/cdrom/cdrom0</code>.
+<pre># pkgadd -d &lt;cdrom&gt;/Solaris_9/Product SUNWgtar
+# pkgadd -d SUNWgtar                 <span class="cmt"># Add downloaded package (bunzip2 first)</span>
+# pkgrm SUNWgtar                     <span class="cmt"># Remove the package</span>
 </pre>
 <h3>FreeBSD</h3>
 <pre># pkg_add -r rsync                   <span class="cmt"># Fetch and install rsync.</span>
@@ -2342,7 +2528,7 @@
 # convert unixtoolbox.pdf unixtoolbox-%03d.png
 # convert *.jpeg images.pdf          <span class="cmt"># Create a simple PDF with all pictures</span>
 </pre>
-Ghostscript can also concatenate multiple pdf files into a single one.
+Ghostscript can also concatenate multiple pdf files into a single one. This only works well if the PDF files are "well behaved".
 <pre># gs -q -sPAPERSIZE=a4 -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -sOutputFile=all.pdf \
 file1.pdf file2.pdf ...              <span class="cmt"># On Windows use '#' instead of '='</span>
 </pre>
@@ -2353,6 +2539,7 @@
 -channels 1 -af-adv force=1 -lameopts preset=medium -lavcopts \
 vcodec=msmpeg4v2:vbitrate=600 -mc 0 vidoein.AVI
 </pre>
+See <a href="http://sox.sourceforge.net/">sox</a> for sound processing.
 
 <h2>Copy an audio cd</h2>
 The program <a rel="nofollow" href="http://xiph.org/paranoia/"><code>cdparanoia</code></a><span class="fn">http://xiph.org/paranoia/</span> can save the audio tracks (FreeBSD port in audio/cdparanoia/), <code>oggenc</code> can encode in Ogg Vorbis format, <code>lame</code> converts to mp3.
@@ -2377,6 +2564,8 @@
 # lpc status                         <span class="cmt"># List all available printers</span>
 # lpc status hp4500                  <span class="cmt"># Check if printer is online and queue length</span>
 </pre>
+Some devices are not postscript and will print garbage when fed with a pdf file. This might be solved with:
+<pre># gs -dSAFER -dNOPAUSE -sDEVICE=deskjet -sOutputFile=\|lpr file.pdf</pre>
 </div>
 
 <div id="databases"><h1><a>Databases</a></h1>
@@ -2454,7 +2643,7 @@
 # mysql -u root -psecret &lt; full.dump
 </pre>
 Here is "secret" the mysql root password, there is no space after -p. When the -p option is used alone (w/o password), the password is asked at the command prompt.
-</div>
+
 <h2 id="sqlite">SQLite</h2>
 <a href="http://www.sqlite.org">SQLite</a><span class="fn">http://www.sqlite.org</span> is a small powerfull self-contined, serverless, zero-configuration SQL database.
 <h3>Dump and restore</h3>
@@ -2464,6 +2653,7 @@
 </pre>
 <h3>Convert 2.x to 3.x database</h3>
 <pre>sqlite database_v2.db .dump | sqlite3 database_v3.db</pre>
+</div>
 
 <div id="quota"><h1><a>Disk Quota</a></h1>
 A disk quota allows to limit the amount of disk space and/or the number of files a user or (or member of group) can use. The quotas are allocated on a per-file system basis and are enforced by the kernel.
@@ -2612,7 +2802,7 @@
 </div>
 
 <div id="scripting"><h1><a>Scripting</a></h1>
-<p class="xrefp"><a class="xrefp" href="#bournebasics">Basics</a> | <a class="xrefp" href="#bourneexample">Script example</a> | <a class="xrefp" href="#sed">sed/useful commands</a></p>
+<p class="xrefp"><a class="xrefp" href="#bournebasics">Basics</a> | <a class="xrefp" href="#bourneexample">Script example</a> | <a class="xrefp" href="#sed">sed</a> | <a class="xrefp" href="#regex">Regular Expressions</a> | <a class="xrefp" href="#shcmd">useful commands</a></p>
 The Bourne shell (/bin/sh) is present on all Unix installations and scripts written in this language are (quite) portable; <code>man 1 sh</code> is a good reference.
 
 <h2 id="bournebasics">Basics</h2>
@@ -2699,6 +2889,7 @@
 </pre>
 
 <h2 id="sed">Some sed commands</h2>
+Here is <a href="http://student.northpark.edu/pemente/sed/sed1line.txt">the one liner gold mine</a><span class="fn">http://student.northpark.edu/pemente/sed/sed1line.txt</span>. And a good <a href="http://www.grymoire.com/Unix/Sed.html">introduction and tutorial to sed</a><span class="fn">http://www.grymoire.com/Unix/Sed.html</span>.
 <pre>sed 's/string1/string2/g'                    <span class="cmt"># Replace string1 with string2</span>
 sed -i 's/wroong/wrong/g' *.txt              <span class="cmt"># Replace a recurring word with g</span>
 sed 's/\(.*\)1/\12/g'                        <span class="cmt"># Modify anystring1 to anystring2</span>
@@ -2708,8 +2899,25 @@
 sed 's/[ \t]*$//'                            <span class="cmt"># Remove trailing spaces (use tab as \t)</span>
 sed 's/^[ \t]*//;s/[ \t]*$//'                <span class="cmt"># Remove leading and trailing spaces</span>
 sed 's/[^*]/[&amp;]/'                            <span class="cmt"># Enclose first char with [] top-&gt;[t]op</span>
+sed = file | sed 'N;s/\n/\t/' > file.num     <span class="cmt"># Number lines on a file</span>
+</pre>
+
+<h2 id="regex">Regular Expressions</h2>
+Some basic regular expression useful for sed too. See <a href="http://www.regular-expressions.info/reference.html">Basic Regex Syntax</a><span class="fn">http://www.regular-expressions.info/reference.html</span> for a good primer.
+<pre>[\^$.|?*+()                          <span class="cmt"># special characters any other will match themselves</span>
+\                                    <span class="cmt"># escapes special characters and treat as literal</span>
+*                                    <span class="cmt"># repeat the previous item zero or more times</span>
+.                                    <span class="cmt"># single character except line break characters</span>
+.*                                   <span class="cmt"># match zero or more characters</span>
+^                                    <span class="cmt"># match at the start of a line/string</span>
+$                                    <span class="cmt"># match at the end of a line/string</span>
+.$                                   <span class="cmt"># match a single character at the end of line/string</span>
+^ $                                  <span class="cmt"># match line with a single space</span>
+[^A-Z]                               <span class="cmt"># match any line beginning with any char from A to Z</span>
 </pre>
+
 <h2 id="shcmd">Some useful commands</h2>
+The following commands are useful to include in a script or as one liners.
 <pre>sort -t. -k1,1n -k2,2n -k3,3n -k4,4n         <span class="cmt"># Sort IPv4 ip addresses</span>
 echo 'Test' | tr '[:lower:]' '[:upper:]'     <span class="cmt"># Case conversion</span>
 echo foo.bar | cut -d . -f 1                 <span class="cmt"># Returns foo</span>
@@ -2723,6 +2931,14 @@
 
 testuser=$(cat /usr/local/etc/apache2/passwd | grep -v \    <span class="cmt"># Check user in passwd</span>
 root | grep -v \*: | awk -F":" '{ printf("%s\n", $1) }' | grep ^user$)
+:(){ :|:&amp; };:                                <span class="cmt"># bash fork bomb. Will kill your machine</span>
+tail +2 file > file2                         <span class="cmt"># remove the first line from file</span>
+</pre>
+I use this little trick to change the file extension for many files at once. For example from .cxx to .cpp. Test it first without the <code>| sh</code> at the end. You can also do this with the command <code>rename</code> if installed. Or with bash builtins.
+<pre># ls *.cxx | awk -F. '{print "mv "$0" "$1".cpp"}' | sh
+# ls *.c | sed "s/.*/cp &amp; &amp;.$(date "+%Y%m%d")/" | sh <span class="cmt"># e.g. copy *.c to *.c.20080401</span>
+# rename .cxx .cpp *.cxx                             <span class="cmt"># Rename all .cxx to cpp</span>
+# for i in *.cxx; do mv $i ${i%%.cxx}.cpp; done      <span class="cmt"># with bash builtins</span>
 </pre>
 </div>
 
@@ -2851,18 +3067,17 @@
   <tr><td><a href="http://unixguide.net/unixguide.shtml">Unix guide cross reference</a> </td><td>unixguide.net/unixguide.shtml</td></tr>
   <tr><td><a rel="nofollow" href="http://www.linuxguide.it/linux_commands_line_en.htm">Linux commands line list</a> </td><td>www.linuxguide.it/commands_list.php</td></tr>
   <tr><td><a rel="nofollow" href="http://www.pixelbeat.org/cmdline.html">Short Linux reference</a> </td><td>www.pixelbeat.org/cmdline.html</td></tr>
+  <tr><td><a href="http://www.shell-fu.org">Little command line goodies</a> </td><td>www.shell-fu.org</td></tr>
 </table>
 </div>
 
 <p class="last">That's all folks!</p>
 
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-This document: "Unix Toolbox revision 11" is licensed under a <a rel="nofollow" href="http://creativecommons.org/licenses/by-sa/3.0/">Creative Commons Licence [Attribution - Share Alike]</a>. &#169; <a href="mailto:c_at_cb.vu">Colin Barschel</a> 2007-2008. Some rights reserved.
+This document: "Unix Toolbox revision 12" is licensed under a <a rel="nofollow" href="http://creativecommons.org/licenses/by-sa/3.0/">Creative Commons Licence [Attribution - Share Alike]</a>. &#169; <a href="mailto:c_at_cb.vu">Colin Barschel</a> 2007-2008. Some rights reserved.
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