The following is a great memo for a lot of bash shortcuts.
Original link : HowToGeek
CTRL Key Bound
Ctrl + a – Jump to the start of the line
Ctrl + b – Move back a char
Ctrl + c – Terminate the command
Ctrl + d – Exit the current shell
Ctrl + e – Jump to the end of the line
Ctrl + f – Move forward a char
Ctrl + h – Same as backspace
Ctrl + k – Delete to EOL
Ctrl + l – Clear the screen
Ctrl + r – Search the history backwards
Ctrl + R – Search the history backwards with multi occurrence
Ctrl + t : Swap the last two characters before the cursor
Ctrl + u – Delete backward from cursor
Ctrl + w : Delete the word before the cursor
Ctrl + xx – Move between EOL and current cursor position
Ctrl + x @ – Show possible hostname completions
Ctrl + z – Suspend/ Stop the command. “fg” restores the suspended command.
ALT Key Bound
Alt + < – Move to the first line in the history
Alt + > – Move to the last line in the history
Alt + ? – Show current completion list
Alt + * – Insert all possible completions
Alt + / – Attempt to complete filename
Alt + . – Yank last argument to previous command
Alt + b – Move backward
Alt + c – Capitalize the word
Alt + d – Delete word
Alt + f – Move forward
Alt + l – Make word lowercase
Alt + n – Search the history forwards non-incremental
Alt + p – Search the history backwards non-incremental
Alt + r – Recall command
Alt + t – Move words around
Alt + u – Make word uppercase
Alt + back-space – Delete backward from cursor
More Special Keybindings
$ 2T – All available commands(common) (2T means press the TAB twice)
$ (string)2T – All available commands starting with (string)
$ /2T – Entire directory structure including Hidden one
$ 2T – Only Sub Dirs inside including Hidden one
$ *2T – Only Sub Dirs inside without Hidden one
$ ~2T – All Present Users on system from “/etc/passwd”
$ $2T – All Sys variables
$ @2T – Entries from “/etc/hosts”
$ =2T – Output like ls or dir
Hope this help
Bye
Riccardo
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The following is a simple memo on how to use the three powerful tools above.
It will not be a complete guide, and you should find only a small part of the possible use, but this would be a review only for the most common use (for me) and would not go a deep dive.
Grep
grep : print lines matching a pattern (equals “grep -G” which is the default)
egrep : equals grep -E (interpret extended regexp)
grep -n : line numbered
grep -i : ignore case
grep -c : count matches
grep -v : print non-matching lines
grep -r : recursivity, read all files under each directory
grep pattern file.txt
Will display the lines containing the pattern
grep -c pattern file.txt
Will display how many lines contain the pattern
grep -i pattern file.txt
Will display the lines containing the pattern regardless of the case
grep -A 1 -B 1 pattern output.txt
Will print the one line before (-B) and one line after (-A) the matching pattern
Awk
August 28th, 2009 | 
Author: 
awk '{ print $0 }' file
Output the content of the file
awk '{ print $2 }' file
Output the second field of data of the file, space is the default separator
awk -F ':' '{ print $2 }' file
Same but separator is “:”
Sed
cat file | sed -e 's/old_pattern/new_pattern/g'
sed would replace old_pattern by new_pattern in the output
cat file | sed -e '4,10s/old_pattern/new_pattern/g'
sed would replace old_pattern by new_pattern in the output between line 4 and 10
cat file | sed '/pattern/d'
Delete a pattern
cat file | sed '/pattern/!d'
Delete everything but the pattern (this equals grep “string_to_remove”)
Hope this help
Bye
Riccardo
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This would be another little memo of all the most used (by me) Input/output redirections and pipes.
As other times this would not be a complete guide, and would not go into the deep.
The base :
Standard input (stdin) : 0
Standard output (stdout) : 1
Error output (stderr) : 2
> : output redirection
< : input redirection
>> : append output
| : pass the output to the next utility
|| : execute the next command if the previous failed
&& : execute the next command only if the previous has succeded
Examples :
cat file.txt > /tmp/file.txt
If file.txt exists, the output will be written in /tmp/file.txt
If file.txt doesn’t exist, the error message will be output to the screen while nothing will be written to /tmp/file.txt (but the file will be created if not existing)
cat file.txt 2> /tmp/error_file.txt > /tmp/file.txt
In this case the error message would be written to /tmp/error_file.txt if the file doesn’t exist
cat file.txt 2> /tmp/error_file.txt >> /tmp/file.txt
The error output would still go in error_file.txt while the standard output would be APPENDED to file.txt
cat file1 > file2
Will copy the content of file1 to file2
cat > file3 Hello world
Will write “Hello world” to file3
[/bash]wc < file.txt > count_file.txt[/bash]
This would count the number of lines, words and bytes in file.txt (”wc < file.txt”) and output the result to count_file.txt
Several ways of counting lines etc. :
$ wc file.txt
7 2 17 file.txt
$ wc < file.txt
7 2 17
$ cat file.txt | wc
7 2 17
ls -l test10 > file.txt 2>&1
This would output anything under file.txt
<code>ls -l test10 2>&1 | mail -s “output in a mail” address@domain.com
Any output in a mail
Hope this help
Bye
Riccardo
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This post is not for a sort of “religion war” between Microsoft and VMware.
I’m using daily both Microsoft products with satisfaction (not every time) and VMware.
I love VMware products, and this is not a secret, but before today, I’ve read everything about Microsoft Hyper-V, so I’ve decided to download it and test it.
The following is my opinion about VMware ESXi and Hyper-V comparison, this because Microsoft trying to tell us that his Hypervisor is similar (or better) than VMware one, and because I don’t think so, you can read here the main reasons.
I started using VMware Update Manager almost immediately after its release.
In my opinion another patching software for Microsoft Windows wasn’t needed when WSUS already existed and does a great job at Windows patching.
For the above reason I’m using VMware Update Manager only for patching esx hosts.
One of the most important feauture of Update Manager is that is fully integrated with VMware DRS, so patching an ESX host cause zero-downtime because the host will be put into Maintenance Mode for patching and than become available again.
This process details the Patching of an ESX host. The remediation process involves Migrating Virtual Machines off the host using vMotion, patching and then redistributing workloads via DRS.
1) First of all connect to Virtualcenter and you must enable the Update Manager plugin.
2) Download and install the Plug-in, and enabled it.
3) When you have the plugin enables, you should see another task button and another Tab at cluster level and at host level.
4) The next step is to attach a baseline to cluster (best practice) or to host. It would be better to attach the baseline to cluster because with thi solution you will have all the hosts at the same patchlevel.
A baseline is a collection of patch, defined by some policy, baselines could be “fixed” or “dynamic”, the first one are a manually selected update lists, the second one is an update lists defined by some dynamic choice. Every baseline should be divided “Non Critical” and “Critical” classifications.
5) When you attach a baseline to an object (a cluster or an host) you should select “SCAN FOR UPDATES” and UpdateManager will check the object patchlevel do define which update should be applied to it.
6) When the task has been finished, you should choose “REMEDIATE”, and consider to run this on one host at a time.
7) Choose from the defined baselines which ones you want to apply to the selected host, and define all options requested.
After the above operations, the host will go into “Maintenance Mode” and all running Virtual Machines will be evacuated to other hosts, Update Manager will apply all needed patches rebooting the host if necessary and at the end the host will exit from “Maintenance Mode”.
Hope this help
Bye
Riccardo
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Recently I was trying to move VMware VirtualCenter database from one server to another and found that for 250MB database I have about more than 30GB of transaction log (LDF) files. I wanted to get rid of this file. There are 2-3 methods but the method I’ve used was thew following :
1) Open SQL Management Studio Express
2) Detach the database from the SQL Server Management Studio.
3) Go to the location of transaction log and rename it (don’t delete the file yet!!)
4) Attach the database without the log file. When you do this step make sure you highlight the log file entry in the wizard and remove it. (Final attach would happen only with one file i.e. with the MDF file).
At this point there would be a new log file created by the SQL Server.
5) Edit the database properties, and select the preferred increment policy of your newly created log file, enabling automtic grow, define increment step and also define maximum dimension to avoid the problem above.
4) Delete the log file once the database is attached and you have verified it.
You can save a lot of space with above steps.
I’ve tested this procedure with VMware VirtualCenter 2.5 Update4, Microsoft SQL 2005 Express with the latest service pack, Microsoft Management Studio Express, and all works fine.
If i remeber well, this would work even with SQL 2000.
Hope this help
Bye
Riccardo
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Which Linux distribution is more suitable for you regarding your experience and preferences ?
find it at :
http://www.zegeniestudios.net/ldc/index.php?lang=en
Mine was 100% Debian / 100% Ubuntu
No surprises on that !
Bye
Riccardo
This post will explain how to disable IPv6 in a system running Debian GNU/Linux or Ubuntu Linux.
You should want to disable IPv6 for compatibility reason or if you not plan to use it for speed up your system and/or to avoid loading of unuseful modules on system start up.
For disable the protocol you have to edit
/etc/modprobe.d/aliases
file and change two lines as follow :
#alias net-pf-10 ipv6 net-pf-10 off
You should also tell to your kernel to not load IPv6 module by blacklisting it at the boot, for doing so edit
/etc/modprobe.d/blacklist
file adding the following line :
blacklist ipv6
Reboot your system and check with the following command if the module ipv6 is not present :
lsmod |grep ipv6
You’ve done
Hope this help
Bye
Riccardo
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This is a VERY CLEAR reference from Massimo Re Ferrè (not so strange ….) about Storage Configuration in a VMware Site Recovery Manager Installation.
You could find it here.
Thank you Massimo for the great job
Bye
Riccardo
The following is a list of MySQL useful commands.
# To setup root password (first execution) mysqladmin -u root password 'new_password' # To login to MySQL mysql -u root -p # To create a database create database dbname; # To change database use dbname; # To create a user and assign to it permission to database # Grant permission only from localhost connections GRANT ALL PRIVILEGES ON *.* TO 'username'@'localhost' IDENTIFIED BY 'some_pass' WITH GRANT OPTION; # Grant permission on all connections GRANT ALL PRIVILEGES ON *.* TO 'username'@'%' IDENTIFIED BY 'some_pass' WITH GRANT OPTION; # Manage MySQL export # Copy all db1 content to /backup-db/db1 folder mysqlhotcopy db1 /backup-db/db1 # Create a DB dump to a file mysqldump db1 > db1_dump_db.sql -u root -p
Hope this help
Bye
Riccardo
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Ok, it wuold not be a so important news, but it’s been long time since I said that I need an USB hub that would let you switch each port on or off.
This could save energy, avoid peripherals to be wakened up whenever your computer starts or simply because you won’t be needing one USB peripheral
Buffalo seems to have donevery good job, with what look to be decent switches and an external power supply in case you need to connect devices that need the full 500 mW of power that an USB connection can supply.
Buffalo USB Hub
Bye
Riccardo
This pot will show some useful example on how to use the “grep” command to find an occurency in a Linux system.
Grep searches the input file (or files) for lines containing a match to a given pattern. Whe an occurency math it copies to standard input the line with the occurrency or you should rediret the output whatever you want.
You should simpy invoke grep with the following :
grep 'STRING' filename
The above is a very simple use f grep, infact it check only in a single file searching all the occurency for ‘STRING’.
You should also use it to find ‘STRING1 STRING2′ in all files in your current location, running ::
grep 'STRING1 STRING2' *
or if you want to make the same research on a given path (i.e. all files in /etc) you should use :
grep 'STRING1 STRING2' /etc/*
Notice the use of single quotes; This are not essential but in this example it was required since the name contains a space. Double quotes could also have been used in this example.
In case of too much occurency you should redirect the output o a file to make more comfortable the research, for example using :
grep 'STRING 1 STRING2" /etc/* > /tmp/grepresults.txt
The following is a simple list for Grep Regular Expression
grep can search for complicated pattern to find what you need using some special characters used to create a regular expression:
`.’ The period `.’ matches any single character.
`?’ The preceding item is optional and will be matched at most once.
`*’ The preceding item will be matched zero or more times.
`+’ The preceding item will be matched one or more times.
for example, a regular expression search would be :
grep "\<[A-Za-z].*" file
The search above will search for any word which begins with a letter upper or lower case.
For more details check :
man grep
Hope this help
Bye
Riccardo
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Very often it happens that I must give support to a colleague or a customer on a Linux machine.
It’s very difficult to spell all bash command I will use to check which could be the problem, especially by phone.
When I discover “screen” it was a revelation.
With screen http://www.gnu.org/software/screen/screen.html you should share a linux session with other people.
You should use screen by simply ask to the user you want to assist to type on the console the following command :
screen
So if you can connect to the machine (even with ssh) you should run the following command :
screen -x
to share the same bash session.
Hope this help
Bye
Riccardo
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Taken from Duncan Epping – Yellow Bricks Blog
this is the complete list of VMware HA Advanced Options that you should use configuring a VMware Cluster :
Virtual Machine Monitoring HA advanced options
Hope this help
Bye
Riccardo
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Since this blog creation, early last year, I have published 99 posts — this post is number 100.
If you are a newer reader, the following are the top three posts of all time:
I’d like to take this opportunity to thank all the subscribers and readers.
Riccardo
This should be an example on how to configure a simple HA (High Availability) without VMware Virtual Center in a two hosts configuration. It requires shared storage between the two hosts, and it works great letting save you a lot of money. Obviously it not provide all Virtual Center features, but it works great. When I have some time to waste, I will add also email notification capabilities. The script will check the “other hosts” with some ICMP packet, and if the host don’t answer for 14 times, it will register all the other host’s VMs and power it on automatically, then wait for 16 seconds and execute all tasks again for paranoid sysadmin. I’ll schedule the job execution every minutes, so it will run twice every minute. I think the script is just pretty commented, but if you have any questions, feel free to ask. The only thing you should do will be export in a file all the VMs registered on the two hosts, and put it on both hosts, for doing this you should simply run :
vmware-cmd -l
and copy and paste the output on a text file, or if you are a script addicted, you should execute on the first host :
vmware-cmd -l | sed 's/\ /\\ /g' > /root/esx01
and on the second host :
vmware-cmd -l | sed 's/\ /\\ /g' > /root/esx02
then you should copy the VMs list between the host, using for example scp, with the following syntax :
usage: scp [-pqrvBC1246] [-F config] [-S program] [-P port] [-c cipher] [-i identity] [-l limit] [-o option] [[user@]host1:]file1 [...] [[user@]host2:]file2
And finally here’s the script :
#!/bin/bash
#
# Manual VMware HA script for two host configuration
# You should keep updated the /root/esx0X file on both hosts if you add or remove VMs
#
# Script created by Riccardo Riva
# Script created 2009/06/29
#
# ESX01 – 10.10.10.11 (VMs list on /root/esx01 on both hosts)
# ESX02 – 10.10.10.12 (VMs list on /root/esx02 on both hosts)
#
# Schedule this script to be executed every minutes by executing ‘crontab -e’ and add the following
# * * * * * /somewhere/this_script.sh
#
# Remeber to assign executable permissions to this script by running ‘chmod +x this_script.sh’
# Modify only the following variables according to your installation
HOSTtoCHECK=10.10.10.11
HOSTtoCHECK_VMs=/root/esx01
# Do not change nothing below this line
if ! ping -c 14 $HOSTtoCHECK > /dev/null; then
while read line
do
vmware-cmd -s register “${line}” && vmware-cmd “${line}” start ;
done < $HOSTtoCHECK_VMs
fi
sleep 16
if ! ping -c 14 $HOSTtoCHECK > /dev/null; then
while read line
do
vmware-cmd -s register “${line}” && vmware-cmd “${line}” start ;
done < $HOSTtoCHECK_VMs
fi
Hope this help
Bye
Riccardo
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The following is a simple script to monitor a Software Raid configuration on a Linux System.
It execute a /proc/mdstat check to search a ‘blocks_’ occurency which indicates problems on the Raid system and in case of match it notify the system administrator with a mail message.
It should be very useful for non-presidiated system, even if I always prefer Hardware Raid.
#!/bin/bash # # Script created by Riccardo Riva # http://www.riccardoriva.com # # It check a Software Raid subsystem and notify by mail any occurency problem # Define variable LOG_FILE=/tmp/raid-check.log SYSTEM=`uname --nodename` MAILTO='systemadmin@mail.exp' # Checking /proc/mdstat cat /proc/mdstat | grep 'blocks.*_' > $LOG_FILE # Define function in case of problems detected if [ $? -eq 0 ] then echo "The $SYSTEM system has RAID failures on it." >> $LOG_FILE echo "Below is the output from /proc/mdstat" >> $LOG_FILE echo "===========================================" >> $LOG_FILE cat /proc/mdstat >> $LOG_FILE echo "===========================================" >> $LOG_FILE cat $LOG_FILE | mail -s 'URGENT: RAID disk failure detected' $MAILTO fi # Deleting log file rm -f >> $LOG_FILE # Exit exit 0
Save the file above as /usr/local/bin/raidcheck.sh and assign to it correct permission and ownership with the folowing :
chmod 700 /usr/local/bin/raidcheck.sh chown root:nobody /usr/local/bin/raidcheck.sh
Change the email address variable with a real email address who will receive the notification.
You should now schedule the script execution at every time interval you want (i.e. twice a day, or hourly if you are paranoic).
Remember that is better to be paranoic that have a degraded system with unrecoverable data.
Hope this help
Bye
Riccardo
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Hi all, the following will be a quick and dirt list of commands for use “dd” in a linux system for various task.
First of all you should create an Hard Disk Image, for example if you want to create an image of your /dev/sda device, you should have another disk (with a writable partition) (i.e. /dev/sdb) with a directory (i.e. /home mounted on it) and simply type :
dd if=/dev/sda of=/home/sda.bin
Or even a partition backup using the same disk device for source and destination like the following (if for example you have /home mounted on /dev/sda2) :
dd if=/dev/sda1 of=/home/sda1.bin
You should even create a compress image of the same disk above, using GZIP, simply type the following :
dd if=/dev/sda1 | gzip > /home/sda1.bin.gz
One of the most useful use of dd (it’s saved my life a lot of time) will be :
dd if=/dev/sda of=sda.boot.mbr bs=512 count=1
With the above command, you have backuped up your MBR (Master Boot Record) of your /dev/sda device and in case of disaster you should restore it, for example booting with a live CD using the following :
dd if=sda.boot.mbr of=/dev/sda bs=512 count=1
You should also create a manual RAID1 between two disk by executing the followinf script with a cron job :
#!/bin/sh # LOG="/var/log/mirror.log" ADMIN="yourmail@yourprovider.ext" ERROR=0 echo `/bin/date` >$LOG 2>&1 /bin/dd if=/dev/sda of=/dev/sdb bs=1M >>$LOG 2>&1 ERROR=$? echo `/bin/date` >>$LOG 2>&1 if [ $ERROR -ne 0 ]; then cat $LOG | /bin/mail -s "Report mirror `uname -n`" $ADMIN fi
The above sript will copy the entire /dev/sda to /dev/sdb logging the process and send an email to your email address at the end for debug and monitoring purpose.
If the first hard disk (/dev/sda) fail, you should phisicaly umount it, and subsitute it with /dev/sdb then reboot the system.
Hope this help
Bye
Riccardo
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This simple post will show how to configure Ethernet Bonding on two (or more) network interfaces on RHEL 5 or CentOS 5.
I’ve tested this configuration on a CentOS 5.2 with kernel 2.6.18-92.1.22.el5 as you could see below :
uname -a Linux serverlab.riccardoriva.local 2.6.18-92.1.22.el5 #1 SMP Tue Dec 16 11:57:43 EST 2008 x86_64 x86_64 x86_64 GNU/Linux cat /etc/redhat-release CentOS release 5.2 (Final)
If you want to create a bonding on two interface (i.e. eth0 and eth1) you should do the following :
Edit /etc/sysconfig/network-scripts/ifcfg-eth0
# Bonding eth0 to bond0 DEVICE=eth0 BOOTPROTO=none ONBOOT=yes MASTER=bond0 SLAVE=yes USERCTL=NO
Edit /etc/sysconfig/network-scripts/ifcfg-eth1
# Bonding eth1 to bond0 BOOTPROTO=none ONBOOT=yes MASTER=bond0 SLAVE=yes USERCTL=NO
Copy /etc/sysconfig/network-scripts/ifcfg-eth1 to /etc/sysconfig/network-scripts/ifcfg-bond0 to keep the same file permission by executing the following commands :
cd /etc/sysconfig/network-scripts copy ifcfg-eth1 ifcfg-bond0
Edit /etc/sysconfig/network-scripts/ifcfg-bond0
ifcfg-bond0 DEVICE=bond0 BOOTPROTO=none ONBOOT=yes NETWORK=10.100.100.0 NETMASK=255.255.255.0 IPADDR=10.100.100.1 USERCTL=NO
Edit /etc/modprobe.conf adding the following line :
alias bond0 bonding
Reboot your system to let modules be loaded or load it manually with the following command :
insmod bond0 bonding
If you haven’t rebooted your system, restart your network with the following command :
/etc/init.d/network restart
You should check if bonding is working you should look at /proc/net/bonding/bond0 with the following command :
cat /proc/net/bonding/bond0
and you should see something similar to the following :
Ethernet Channel Bonding Driver: v3.2.4 (January 28, 2008) Bonding Mode: load balancing (round-robin) MII Status: up MII Polling Interval (ms): 0 Up Delay (ms): 0 Down Delay (ms): 0 Slave Interface: eth0 MII Status: up Link Failure Count: 0 Permanent HW addr: 00:15:17:88:5a:3c Slave Interface: eth1 MII Status: up Link Failure Count: 0 Permanent HW addr: 00:15:17:88:5a:3d
You’ve done
Hope this help
Bye
Riccardo
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I’m using this script in a lot of Linux Server, especially some file server with a little ERP software written in COBOL with all files in /home/erp.
I’m saving all /home and /etc to have a full backup for disaster recovery purpose.
This scrit will do the following :
- Define variables
- Define DATE
- Create a compress archive of /home and /etc
- Rewind the TAPE
- Write all the data on TAPE
- Verify the TAPE
- Eject the TAPE
Obviously all the output of the above operations will be redirected to a log file fr diagnostic purpose.
- Mail all logged operations to the Server admin
The only prerequisites for let all works is “mail” packages installed on your system and a local mail server configured for routing mail to your “Server Admin” email address, I’m using Postfix, but you coul’d use whatever you want (eg. QMail or EXIM).
Read the rest of this entry »
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