Command privileges
sudo command - run command as root
sudo su – root shell open
sudo su user – open shell as a user
sudo -k – forget your password sudo
gksudo command – sudo visual dialog (GNOME)
kdesudo command – sudo visual dialog (KDE)
sudo visudo – edit / etc / sudoers
gksudo nautilus – root file manager (GNOME)
kdesudo konqueror – root file manager (KDE)
passwd – change your password
Command Network
ifconfig – displays information network
iwconfig – displays information from wireless
sudo iwlist scan – scan wireless networks
sudo /etc/init.d/networking restart – reset the network
(file) /etc/network/interfaces – manual configuration
ifup interface – bring online interface
ifdown interface – disable interface
Commands Display
sudo /etc/init.d/gdm restart – reset X (Gnome)
sudo /etc/init.d/kdm restart – reset X (KDE)
(file) /etc/X11/xorg.conf – show Configuration
sudo dpkg-reconfigure - reconfigure xserver-xorg-phigh - reset configuration X
Ctrl+Alt+Bksp – X display reset if frozen
Ctrl+Alt+FN – switch to tty N
Ctrl+Alt+F7 – switch back to X display
Commands Service System
start service – service to start work (Upstart)
stop service – service to stop working (Upstart)
status service – check if service is running (Upstart)
/etc/init.d/service start – start service (SysV)
/etc/init.d/service stop – stop service (SysV)
/etc/init.d/service status – check service (SysV)
/etc/init.d/service restart – reset service (SysV)
runlevel – get current runlevel
Commands for Firewall
ufw enable – turn on the firewall
ufw disable – turn off the firewall
ufw default allow – allow all connections by default
ufw default deny – drop all connections by default
ufw status – current rules and
ufw allow port – to allow traffic on port
ufw deny port – port block
ufw deny from ip – ip block
Command System
lsb_release -a – get the version of Ubuntu
uname -r – get kernel version
uname -a – get all the information kernel
Commands for Package Manager
apt-get update – refresh updates available
apt-get upgrade – update all packages
apt-get dist-upgrade – version update
apt-get install pkg – installing pkg
apt-get remove pkg – uninstall pkg
apt-get autoremove – removing packages obsotletos
apt-get -f install – try to fix packages
dpkg –configure -a – try to fix a broken package
dpkg -i pkg.deb – install file pkg.deb
(file) /etc/apt/sources.list – list of repositories APT
Special Packages For commands
ubuntu-desktop – Setting the standard Ubuntu
kubuntu-desktop – KDE Desktop
xubuntu-desktop – desktop XFCE
ubuntu-minimal – core earnings Ubuntu
ubuntu-standard – the standard utilities Ubuntu
ubuntu-restricted-extras – not free, but useful
kubuntu-restricted-extras – ditto KDE
xubuntu-restricted-extras – ditto XFCE
build-essential – packages used to compile
linux-image-generic – latest generic kernel image
linux-headers-generic – latest headlines
Applications commands
nautilus – File Manager (GNOME)
dolphin – File Manager (KDE)
konqueror – Web browser (KDE)
kate – text editor (KDE)
gedit – text editor (GNOME)
Installing GRUB using grub-install
In order to install GRUB under a UNIX-like OS (such as gnu), invoke the program grub-install as the superuser (root).
The usage is basically very simple. You only need to specify one argument to the program, namely, where to install the boot loader. The argument has to be either a device file (like ‘/dev/hda’). For example, under Linux the following will install GRUB into the MBR of the first IDE disk:
# grub-install /dev/hda
Likewise, under GNU/Hurd, this has the same effect:
# grub-install /dev/hd0
But all the above examples assume that GRUB should put images under the /boot directory. If you want GRUB to put images under a directory other than /boot, you need to specify the option --boot-directory. The typical usage is that you create a GRUB boot floppy with a filesystem. Here is an example:
# mke2fs /dev/fd0
# mount -t ext2 /dev/fd0 /mnt
# mkdir /mnt/boot
# grub-install --boot-directory=/mnt/boot /dev/fd0
# umount /mnt
Some BIOSes have a bug of exposing the first partition of a USB drive as a floppy instead of exposing the USB drive as a hard disk (they call it “USB-FDD” boot). In such cases, you need to install like this:
# losetup /dev/loop0 /dev/sdb1
# mount /dev/loop0 /mnt/usb
# grub-install --boot-directory=/mnt/usb/bugbios --force --allow-floppy /dev/loop0
This install doesn't conflict with standard install as long as they are in separate directories.
Note that grub-install is actually just a shell script and the real task is done by grub-mkimage and grub-setup. Therefore, you may run those commands directly to install GRUB, without using grub-install. Don't do that, however, unless you are very familiar with the internals of GRUB. Installing a boot loader on a running OS may be extremely dangerous.
Windows: control panel shortcuts
Accessibility Options........................access.cpl
Add New Hardware ........................sysdm.cpl
Add/Remove Programs ........................appwiz.cpl
Date/Time Properties ........................timedate.cpl
Display Properties ........................desk.cpl
FindFast ........................findfast.cpl
Fonts Folder ........................fonts
Internet Properties ........................inetcpl.cpl
Joystick Properties ........................joy.cpl
Keyboard Properties ........................main.cpl keyboard
Microsoft Exchange ........................mlcfg32.cpl
Microsoft Mail Post Office...................wgpocpl.cpl
Modem Properties ........................modem.cpl
Mouse Properties ........................main.cpl
Multimedia Properties........................mmsys.cpl
Network Properties ........................netcpl.cpl
Password Properties ........................password.cpl
PC Card ........................main.cpl pc card (PCMCIA)
Power Management.............................main.cpl power
Power Management.............................powercfg.cpl
Printers Folder ........................printers
Regional Settings ........................intl.cpl
Scanners and Cameras ........................sticpl.cpl
Sound Properties ........................mmsys.cpl sounds
System Properties ........................sysdm.cpl
Add New Hardware ........................sysdm.cpl
Add/Remove Programs ........................appwiz.cpl
Date/Time Properties ........................timedate.cpl
Display Properties ........................desk.cpl
FindFast ........................findfast.cpl
Fonts Folder ........................fonts
Internet Properties ........................inetcpl.cpl
Joystick Properties ........................joy.cpl
Keyboard Properties ........................main.cpl keyboard
Microsoft Exchange ........................mlcfg32.cpl
Microsoft Mail Post Office...................wgpocpl.cpl
Modem Properties ........................modem.cpl
Mouse Properties ........................main.cpl
Multimedia Properties........................mmsys.cpl
Network Properties ........................netcpl.cpl
Password Properties ........................password.cpl
PC Card ........................main.cpl pc card (PCMCIA)
Power Management.............................main.cpl power
Power Management.............................powercfg.cpl
Printers Folder ........................printers
Regional Settings ........................intl.cpl
Scanners and Cameras ........................sticpl.cpl
Sound Properties ........................mmsys.cpl sounds
System Properties ........................sysdm.cpl
Exim Mail Commands in Details
Print a count of the messages in the queue:
[root@localhost]# exim -bpc
Print a listing of the messages in the queue (time queued, size, message-id, sender, recipient):
[root@localhost]# exim -bp
Print a summary of messages in the queue (count, volume, oldest, newest, domain, and totals):
[root@localhost]# exim -bp | exiqsumm
Print what Exim is doing right now:
[root@localhost]# exiwhat
Test how exim will route a given address:
[root@localhost]# exim -bt alias@localdomain.com
#user@thishost.com
<-- alias@localdomain.com
router = localuser, transport = local_delivery
[root@localhost]# exim -bt user@thishost.com
user@thishost.com
router = localuser, transport = local_delivery
[root@localhost]# exim -bt user@remotehost.com
router = lookuphost, transport = remote_smtp
host mail.remotehost.com [1.2.3.4] MX=0
Run a pretend SMTP transaction from the command line, as if it were coming from the given IP address. This will display Exim's checks, ACLs, and filters as they are applied. The message will NOT actually be delivered.
[root@localhost]# exim -bh 192.168.11.22
Display all of Exim's configuration settings:
[root@localhost]# exim -bP
Searching the queue with exiqgrep
Exim includes a utility that is quite nice for grepping through the queue, called exiqgrep. Learn it. Know it. Live it. If you're not using this, and if you're not familiar with the various flags it uses, you're probably doing things the hard way, like piping `exim -bp` into awk, grep, cut, or `wc -l`. Don't make life harder than it already is.
First, various flags that control what messages are matched. These can be combined to come up with a very particular search.
Use -f to search the queue for messages from a specific sender:
[root@localhost]# exiqgrep -f [luser]@domain
Use -r to search the queue for messages for a specific recipient/domain:
[root@localhost]# exiqgrep -r [luser]@domain
Use -o to print messages older than the specified number of seconds. For example, messages older than 1 day:
[root@localhost]# exiqgrep -o 86400 [...]
Use -y to print messages that are younger than the specified number of seconds. For example, messages less than an hour old:
[root@localhost]# exiqgrep -y 3600 [...]
Use -s to match the size of a message with a regex. For example, 700-799 bytes:
[root@localhost]# exiqgrep -s '^7..$' [...]
Use -z to match only frozen messages, or -x to match only unfrozen messages.
There are also a few flags that control the display of the output.
Use -i to print just the message-id as a result of one of the above two searches:
[root@localhost]# exiqgrep -i [ -r | -f ] ...
Use -c to print a count of messages matching one of the above searches:
[root@localhost]# exiqgrep -c ...
Print just the message-id of the entire queue:
[root@localhost]# exiqgrep -i
Managing the queue
The main exim binary (/usr/sbin/exim) is used with various flags to make things happen to messages in the queue. Most of these require one or more message-IDs to be specified in the command line, which is where `exiqgrep -i` as described above really comes in handy.
Start a queue run:
[root@localhost]# exim -q -v
Start a queue run for just local deliveries:
[root@localhost]# exim -ql -v
Remove a message from the queue:
[root@localhost]# exim -Mrm <message-id> [ <message-id> ... ]
Freeze a message:
[root@localhost]# exim -Mf <message-id> [ <message-id> ... ]
Thaw a message:
[root@localhost]# exim -Mt <message-id> [ <message-id> ... ]
Deliver a message, whether it's frozen or not, whether the retry time has been reached or not:
[root@localhost]# exim -M <message-id> [ <message-id> ... ]
Deliver a message, but only if the retry time has been reached:
[root@localhost]# exim -Mc <message-id> [ <message-id> ... ]
Force a message to fail and bounce as "cancelled by administrator":
[root@localhost]# exim -Mg <message-id> [ <message-id> ... ]
Remove all frozen messages:
[root@localhost]# exiqgrep -z -i | xargs exim -Mrm
Remove all messages older than five days (86400 * 5 = 432000 seconds):
[root@localhost]# exiqgrep -o 432000 -i | xargs exim -Mrm
Freeze all queued mail from a given sender:
[root@localhost]# exiqgrep -i -f luser@example.tld | xargs exim -Mf
View a message's headers:
[root@localhost]# exim -Mvh <message-id>
View a message's body:
[root@localhost]# exim -Mvb <message-id>
View a message's logs:
[root@localhost]# exim -Mvl <message-id>
Add a recipient to a message:
[root@localhost]# exim -Mar <message-id> <address> [ <address> ... ]
Edit the sender of a message:
[root@localhost]# exim -Mes <message-id> <address>
Searching the logs with exigrep
The exigrep utility (not to be confused with exiqgrep) is used to search an exim log for a string or pattern. It will print all log entries with the same internal message-id as those that matched the pattern, which is very handy since any message will take up at least three lines in the log. exigrep will search the entire content of a log entry, not just particular fields.
One can search for messages sent from a particular IP address:
[root@localhost]# exigrep '<= .* \[12.34.56.78\] ' /path/to/exim_log
Search for messages sent to a particular IP address:
[root@localhost]# exigrep '=> .* \[12.34.56.78\]' /path/to/exim_log
This example searches for outgoing messages, which have the "=>" symbol, sent to "user@domain.tld". The pipe to grep for the "<=" symbol will match only the lines with information on the sender - the From address, the sender's IP address, the message size, the message ID, and the subject line if you have enabled logging the subject. The purpose of doing such a search is that the desired information is not on the same log line as the string being searched for.
[root@localhost]# exigrep '=> .*user@domain.tld' /path/to/exim_log | fgrep '<='
Generate and display Exim stats from a logfile:
[root@localhost]# eximstats /path/to/exim_mainlog
Same as above, with less verbose output:
[root@localhost]# eximstats -ne -nr -nt /path/to/exim_mainlog
Same as above, for one particular day:
[root@localhost]# fgrep YYYY-MM-DD /path/to/exim_mainlog | eximstats
To delete all queued messages containing a certain string in the body:
[root@localhost]# grep -lr 'a certain string' /var/spool/exim/input/ | \
sed -e 's/^.*\/\([a-zA-Z0-9-]*\)-[DH]$/\1/g' | xargs exim -Mrm
Note that the above only delves into /var/spool/exim in order to grep for queue files with the given string, and that's just because exiqgrep doesn't have a feature to grep the actual bodies of messages. If you are deleting these files directly, YOU ARE DOING IT WRONG! Use the appropriate exim command to properly deal with the queue.
If you have to feed many, many message-ids (such as the output of an `exiqgrep -i` command that returns a lot of matches) to an exim command, you may exhaust the limit of your shell's command line arguments. In that case, pipe the listing of message-ids into xargs to run only a limited number of them at once. For example, to remove thousands of messages sent from hero@linux-geek.com:
[root@localhost]# exiqgrep -i -f '<hero@linux-geek.com>' | xargs exim -Mrm
[root@localhost]# exim -bpc
Print a listing of the messages in the queue (time queued, size, message-id, sender, recipient):
[root@localhost]# exim -bp
Print a summary of messages in the queue (count, volume, oldest, newest, domain, and totals):
[root@localhost]# exim -bp | exiqsumm
Print what Exim is doing right now:
[root@localhost]# exiwhat
Test how exim will route a given address:
[root@localhost]# exim -bt alias@localdomain.com
#user@thishost.com
<-- alias@localdomain.com
router = localuser, transport = local_delivery
[root@localhost]# exim -bt user@thishost.com
user@thishost.com
router = localuser, transport = local_delivery
[root@localhost]# exim -bt user@remotehost.com
router = lookuphost, transport = remote_smtp
host mail.remotehost.com [1.2.3.4] MX=0
Run a pretend SMTP transaction from the command line, as if it were coming from the given IP address. This will display Exim's checks, ACLs, and filters as they are applied. The message will NOT actually be delivered.
[root@localhost]# exim -bh 192.168.11.22
Display all of Exim's configuration settings:
[root@localhost]# exim -bP
Searching the queue with exiqgrep
Exim includes a utility that is quite nice for grepping through the queue, called exiqgrep. Learn it. Know it. Live it. If you're not using this, and if you're not familiar with the various flags it uses, you're probably doing things the hard way, like piping `exim -bp` into awk, grep, cut, or `wc -l`. Don't make life harder than it already is.
First, various flags that control what messages are matched. These can be combined to come up with a very particular search.
Use -f to search the queue for messages from a specific sender:
[root@localhost]# exiqgrep -f [luser]@domain
Use -r to search the queue for messages for a specific recipient/domain:
[root@localhost]# exiqgrep -r [luser]@domain
Use -o to print messages older than the specified number of seconds. For example, messages older than 1 day:
[root@localhost]# exiqgrep -o 86400 [...]
Use -y to print messages that are younger than the specified number of seconds. For example, messages less than an hour old:
[root@localhost]# exiqgrep -y 3600 [...]
Use -s to match the size of a message with a regex. For example, 700-799 bytes:
[root@localhost]# exiqgrep -s '^7..$' [...]
Use -z to match only frozen messages, or -x to match only unfrozen messages.
There are also a few flags that control the display of the output.
Use -i to print just the message-id as a result of one of the above two searches:
[root@localhost]# exiqgrep -i [ -r | -f ] ...
Use -c to print a count of messages matching one of the above searches:
[root@localhost]# exiqgrep -c ...
Print just the message-id of the entire queue:
[root@localhost]# exiqgrep -i
Managing the queue
The main exim binary (/usr/sbin/exim) is used with various flags to make things happen to messages in the queue. Most of these require one or more message-IDs to be specified in the command line, which is where `exiqgrep -i` as described above really comes in handy.
Start a queue run:
[root@localhost]# exim -q -v
Start a queue run for just local deliveries:
[root@localhost]# exim -ql -v
Remove a message from the queue:
[root@localhost]# exim -Mrm <message-id> [ <message-id> ... ]
Freeze a message:
[root@localhost]# exim -Mf <message-id> [ <message-id> ... ]
Thaw a message:
[root@localhost]# exim -Mt <message-id> [ <message-id> ... ]
Deliver a message, whether it's frozen or not, whether the retry time has been reached or not:
[root@localhost]# exim -M <message-id> [ <message-id> ... ]
Deliver a message, but only if the retry time has been reached:
[root@localhost]# exim -Mc <message-id> [ <message-id> ... ]
Force a message to fail and bounce as "cancelled by administrator":
[root@localhost]# exim -Mg <message-id> [ <message-id> ... ]
Remove all frozen messages:
[root@localhost]# exiqgrep -z -i | xargs exim -Mrm
Remove all messages older than five days (86400 * 5 = 432000 seconds):
[root@localhost]# exiqgrep -o 432000 -i | xargs exim -Mrm
Freeze all queued mail from a given sender:
[root@localhost]# exiqgrep -i -f luser@example.tld | xargs exim -Mf
View a message's headers:
[root@localhost]# exim -Mvh <message-id>
View a message's body:
[root@localhost]# exim -Mvb <message-id>
View a message's logs:
[root@localhost]# exim -Mvl <message-id>
Add a recipient to a message:
[root@localhost]# exim -Mar <message-id> <address> [ <address> ... ]
Edit the sender of a message:
[root@localhost]# exim -Mes <message-id> <address>
Searching the logs with exigrep
The exigrep utility (not to be confused with exiqgrep) is used to search an exim log for a string or pattern. It will print all log entries with the same internal message-id as those that matched the pattern, which is very handy since any message will take up at least three lines in the log. exigrep will search the entire content of a log entry, not just particular fields.
One can search for messages sent from a particular IP address:
[root@localhost]# exigrep '<= .* \[12.34.56.78\] ' /path/to/exim_log
Search for messages sent to a particular IP address:
[root@localhost]# exigrep '=> .* \[12.34.56.78\]' /path/to/exim_log
This example searches for outgoing messages, which have the "=>" symbol, sent to "user@domain.tld". The pipe to grep for the "<=" symbol will match only the lines with information on the sender - the From address, the sender's IP address, the message size, the message ID, and the subject line if you have enabled logging the subject. The purpose of doing such a search is that the desired information is not on the same log line as the string being searched for.
[root@localhost]# exigrep '=> .*user@domain.tld' /path/to/exim_log | fgrep '<='
Generate and display Exim stats from a logfile:
[root@localhost]# eximstats /path/to/exim_mainlog
Same as above, with less verbose output:
[root@localhost]# eximstats -ne -nr -nt /path/to/exim_mainlog
Same as above, for one particular day:
[root@localhost]# fgrep YYYY-MM-DD /path/to/exim_mainlog | eximstats
To delete all queued messages containing a certain string in the body:
[root@localhost]# grep -lr 'a certain string' /var/spool/exim/input/ | \
sed -e 's/^.*\/\([a-zA-Z0-9-]*\)-[DH]$/\1/g' | xargs exim -Mrm
Note that the above only delves into /var/spool/exim in order to grep for queue files with the given string, and that's just because exiqgrep doesn't have a feature to grep the actual bodies of messages. If you are deleting these files directly, YOU ARE DOING IT WRONG! Use the appropriate exim command to properly deal with the queue.
If you have to feed many, many message-ids (such as the output of an `exiqgrep -i` command that returns a lot of matches) to an exim command, you may exhaust the limit of your shell's command line arguments. In that case, pipe the listing of message-ids into xargs to run only a limited number of them at once. For example, to remove thousands of messages sent from hero@linux-geek.com:
[root@localhost]# exiqgrep -i -f '<hero@linux-geek.com>' | xargs exim -Mrm
Deleting mail from the mail queue in sendmail
Sendmail does not provide a command-line argument to remove messages from the mail queue. It may be necessary to manually remove messages from the mail queue rather than allowing Sendmail to attempt redelivery of messages for Timeout.queureturn days (5, by default).
The proper way to remove messages from the mail queue is to use the qtool.pl program included in the contrib subdirectory of the Sendmail source code distribution. qtool.pl uses the same file locking mechanism as Sendmail.
Removing "double bounce" messages
The following is a Perl script that calls /usr/local/bin/qtool.pl to remove "double bounce" messages. A "double bounce" is a message that is addressed to a non-existent user and that is sent from an invalid return address. Busy mail relays often have hundreds to thousands of these messages.
The script below will delete a queued message if it is (1) "deferred" (unable to be returned to the sender), (2) being sent from our postmaster email address, and (3) the subject is unique to delivery failure notifications.
#!/usr/bin/perl
use strict;
my $qtool = "/usr/local/bin/qtool.pl";
my $mqueue_directory = "/var/spool/mqueue";
my $messages_removed = 0;
use File::Find;
# Recursively find all files and directories in $mqueue_directory
find(\&wanted, $mqueue_directory);
sub wanted {
# Is this a qf* file?
if ( /^qf(\w{14})/ ) {
my $qf_file = $_;
my $queue_id = $1;
my $deferred = 0;
my $from_postmaster = 0;
my $delivery_failure = 0;
my $double_bounce = 0;
open (QF_FILE, $_);
while(<QF_FILE>) {
$deferred = 1 if ( /^MDeferred/ );
$from_postmaster = 1 if ( /^S<>$/ );
$delivery_failure = 1 if \
( /^H\?\?Subject: DELIVERY FAILURE: (User|Recipient)/ );
if ( $deferred && $from_postmaster && $delivery_failure ) {
$double_bounce = 1;
last;
}
}
close (QF_FILE);
if ($double_bounce) {
print "Removing $queue_id...\n";
system "$qtool", "-d", $qf_file;
$messages_removed++;
}
}
}
print "\n$messages_removed total \"double bounce\" message(s) removed from ";
print "mail queue.\n";
Queued mail by domain
The following Perl script will show all queued mail by domain. A message may be counted more than once if it has multiple envelope recipients from different domains.
#!/usr/bin/perl
use strict;
my $mqueue_directory = "/var/spool/mqueue";
my %occurrences;
use File::Find;
# Recursively find all files and directories in $mqueue_directory
find(\&wanted, $mqueue_directory);
sub wanted {
# Is this a qf* file?
if ( /^qf\w{14}/ ) {
open (QF_FILE, $_);
while(<QF_FILE>) {
# Lines beginning with R contain an envelope recipient
if ( /^R.*:<.*\@(.*)>$/ ) {
my $domain = lc($1);
# Add 1 to the %occurrences hash
$occurrences{$domain}++;
}
}
}
}
# Subroutine to sort hash by ascending value
sub hashValueAscendingNum {
$occurrences{$a} <=> $occurrences{$b};
}
# Print sorted results
foreach my $key (sort hashValueAscendingNum (keys(%occurrences))) {
print "$occurrences{$key} $key\n";
}
Removing mail by domain
The following Perl script will remove all mail in the mail queue addressed to domain. Messages with multiple envelope recipients to different domains will not be deleted.
#!/usr/bin/perl
use strict;
# Exit immediately if domain was not specified as command-line argument
if (!(defined($ARGV[0]))) {
(my $basename = $0) =~ s!^.*/!!;
print "Usage: $basename domain\n";
exit 1;
}
# Convert domain supplied as command-line argument to lowercase
my $domain_to_remove = lc($ARGV[0]);
my $qtool = "/usr/local/bin/qtool.pl";
my $mqueue_directory = "/var/spool/mqueue";
my $messages_removed = 0;
use File::Find;
# Recursively find all files and directories in $mqueue_directory
find(\&wanted, $mqueue_directory);
sub wanted {
# Is this a qf* file?
if ( /^qf\w{14}/ ) {
my $QF_FILE = $_;
my $envelope_recipients = 0;
my $match = 1;
open (QF_FILE, $_);
while(<QF_FILE>) {
# If any of the envelope recipients contain a domain other than
# $domain_to_remove, do not match the message
if ( /^R.*:<.*\@(.*)>$/ ) {
my $recipient_domain = lc($1);
$envelope_recipients++;
if ($recipient_domain ne $domain_to_remove) {
$match = 0;
last;
}
}
}
close (QF_FILE);
# $QF_FILE may not contain an envelope recipient at the time it is opened
# and read. Do not match $QF_FILE in that case.
if ($match == 1 && $envelope_recipients != 0) {
print "Removing $QF_FILE...\n";
system "$qtool", "-d", $QF_FILE;
$messages_removed++;
}
}
}
print "$messages_removed total message(s) removed from mail queue.\n";
Queued mail by email address
The following Perl script will show all queued mail by email address. A message may be counted more than once if it has multiple envelope recipients.
#!/usr/bin/perl
use strict;
my $mqueue_directory = "/var/spool/mqueue";
my %occurrences;
use File::Find;
# Recursively find all files and directories in $mqueue_directory
find(\&wanted, $mqueue_directory);
sub wanted {
# Is this a qf* file?
if ( /^qf\w{14}/ ) {
open (QF_FILE, $_);
while(<QF_FILE>) {
# Lines beginning with R contain an envelope recipient
if ( /^R.*:<(.*)>$/ ) {
my $domain = lc($1);
# Add 1 to the %occurrences hash
$occurrences{$domain}++;
}
}
}
}
# Subroutine to sort hash by ascending value
sub hashValueAscendingNum {
$occurrences{$a} <=> $occurrences{$b};
}
# Print sorted results
foreach my $key (sort hashValueAscendingNum (keys(%occurrences))) {
print "$occurrences{$key} $key\n";
}
Removing mail by email address
The following Perl script will remove all mail in the mail queue addressed to email_address. Messages with multiple envelope recipients will not be deleted.
#!/usr/bin/perl
use strict;
# Exit immediately if email_address was not specified as command-line argument
if (!(defined($ARGV[0]))) {
(my $basename = $0) =~ s!^.*/!!;
print "Usage: $basename email_address\n";
exit 1;
}
# Convert email address supplied as command-line argument to lowercase
my $address_to_remove = lc($ARGV[0]);
my $qtool = "/usr/local/bin/qtool.pl";
my $mqueue_directory = "/var/spool/mqueue";
my $messages_removed = 0;
use File::Find;
# Recursively find all files and directories in $mqueue_directory
find(\&wanted, $mqueue_directory);
sub wanted {
# Is this a qf* file?
if ( /^qf\w{14}/ ) {
my $QF_FILE = $_;
my $envelope_recipients = 0;
my $match = 1;
open (QF_FILE, $_);
while(<QF_FILE>) {
# If any of the envelope recipients contain an email address other than
# $address_to_remove, do not match the message
if ( /^R.*:<(.*)>$/ ) {
my $recipient_address = lc($1);
$envelope_recipients++;
if ($recipient_address ne $address_to_remove) {
$match = 0;
last;
}
}
}
close (QF_FILE);
# $QF_FILE may not contain an envelope recipient at the time it is opened
# and read. Do not match $QF_FILE in that case.
if ($match == 1 && $envelope_recipients != 0) {
print "Removing $QF_FILE...\n";
system "$qtool", "-d", $QF_FILE;
$messages_removed++;
}
}
}
print "$messages_removed total message(s) removed from mail queue.\n";
Older notes
Note: the preferred method of queue removal is to use qtool.pl as illustrated above.
In order to remove mail from the queue, you have to delete the df* and qf* files from your mail queue directory, generally /var/spool/mqueue. The qf* file is the header of the message and the control file, and the df* file is the body of the message.
script to move undeliverable email in our /var/spool/mqueue mail queue to an alternate /tmp/mqueue directory.
#!/bin/sh
if [ -z $@ ] ; then
echo "Usage: $0 email_address"
exit 1
fi
for i in `(cd /var/spool/mqueue; grep -l "To:.*$1" qf* | cut -c3-)`
do
mv /var/spool/mqueue/*$i /tmp/mqueue
done
If you have multiple mail queues, such as q1, q2, q3, q4, and q5, you can use the following script:
#!/bin/sh
if [ -z $@ ] ; then
echo "Usage: $0 email_address"
exit 1
fi
for i in q1 q2 q3 q4 q5
do
for j in `(cd /var/spool/mqueue/$i; grep -l "To:.*$1" qf* | cut -c3-)`
do
mv /var/spool/mqueue/$i/*$j /tmp/mqueue
done
done
For example, running the script while passing the command-line argument badsender@baddomain.com will look for each qf* file in the mail queue containing To:.*badsender@baddomain.com. The regular
expression .* will match zero or more occurrences of any characters, numbers, or whitespace. For example, it would match:
To: badsender@baddomain.com
To: Bad Sender <badsender@baddomain.com>
The script then moves any other files (i.e. the body of the message) in the mail queue with the same Sendmail message ID to the alternate directory. It does this with the cut -c3- command, as the Sendmail message ID is the 3rd through the last character.
The mail is moved to /tmp/mqueue. If you are confident that you do not want the messages, you can delete them from this directory, or you could change the script to remove the files.
The proper way to remove messages from the mail queue is to use the qtool.pl program included in the contrib subdirectory of the Sendmail source code distribution. qtool.pl uses the same file locking mechanism as Sendmail.
Removing "double bounce" messages
The following is a Perl script that calls /usr/local/bin/qtool.pl to remove "double bounce" messages. A "double bounce" is a message that is addressed to a non-existent user and that is sent from an invalid return address. Busy mail relays often have hundreds to thousands of these messages.
The script below will delete a queued message if it is (1) "deferred" (unable to be returned to the sender), (2) being sent from our postmaster email address, and (3) the subject is unique to delivery failure notifications.
#!/usr/bin/perl
use strict;
my $qtool = "/usr/local/bin/qtool.pl";
my $mqueue_directory = "/var/spool/mqueue";
my $messages_removed = 0;
use File::Find;
# Recursively find all files and directories in $mqueue_directory
find(\&wanted, $mqueue_directory);
sub wanted {
# Is this a qf* file?
if ( /^qf(\w{14})/ ) {
my $qf_file = $_;
my $queue_id = $1;
my $deferred = 0;
my $from_postmaster = 0;
my $delivery_failure = 0;
my $double_bounce = 0;
open (QF_FILE, $_);
while(<QF_FILE>) {
$deferred = 1 if ( /^MDeferred/ );
$from_postmaster = 1 if ( /^S<>$/ );
$delivery_failure = 1 if \
( /^H\?\?Subject: DELIVERY FAILURE: (User|Recipient)/ );
if ( $deferred && $from_postmaster && $delivery_failure ) {
$double_bounce = 1;
last;
}
}
close (QF_FILE);
if ($double_bounce) {
print "Removing $queue_id...\n";
system "$qtool", "-d", $qf_file;
$messages_removed++;
}
}
}
print "\n$messages_removed total \"double bounce\" message(s) removed from ";
print "mail queue.\n";
Queued mail by domain
The following Perl script will show all queued mail by domain. A message may be counted more than once if it has multiple envelope recipients from different domains.
#!/usr/bin/perl
use strict;
my $mqueue_directory = "/var/spool/mqueue";
my %occurrences;
use File::Find;
# Recursively find all files and directories in $mqueue_directory
find(\&wanted, $mqueue_directory);
sub wanted {
# Is this a qf* file?
if ( /^qf\w{14}/ ) {
open (QF_FILE, $_);
while(<QF_FILE>) {
# Lines beginning with R contain an envelope recipient
if ( /^R.*:<.*\@(.*)>$/ ) {
my $domain = lc($1);
# Add 1 to the %occurrences hash
$occurrences{$domain}++;
}
}
}
}
# Subroutine to sort hash by ascending value
sub hashValueAscendingNum {
$occurrences{$a} <=> $occurrences{$b};
}
# Print sorted results
foreach my $key (sort hashValueAscendingNum (keys(%occurrences))) {
print "$occurrences{$key} $key\n";
}
Removing mail by domain
The following Perl script will remove all mail in the mail queue addressed to domain. Messages with multiple envelope recipients to different domains will not be deleted.
#!/usr/bin/perl
use strict;
# Exit immediately if domain was not specified as command-line argument
if (!(defined($ARGV[0]))) {
(my $basename = $0) =~ s!^.*/!!;
print "Usage: $basename domain\n";
exit 1;
}
# Convert domain supplied as command-line argument to lowercase
my $domain_to_remove = lc($ARGV[0]);
my $qtool = "/usr/local/bin/qtool.pl";
my $mqueue_directory = "/var/spool/mqueue";
my $messages_removed = 0;
use File::Find;
# Recursively find all files and directories in $mqueue_directory
find(\&wanted, $mqueue_directory);
sub wanted {
# Is this a qf* file?
if ( /^qf\w{14}/ ) {
my $QF_FILE = $_;
my $envelope_recipients = 0;
my $match = 1;
open (QF_FILE, $_);
while(<QF_FILE>) {
# If any of the envelope recipients contain a domain other than
# $domain_to_remove, do not match the message
if ( /^R.*:<.*\@(.*)>$/ ) {
my $recipient_domain = lc($1);
$envelope_recipients++;
if ($recipient_domain ne $domain_to_remove) {
$match = 0;
last;
}
}
}
close (QF_FILE);
# $QF_FILE may not contain an envelope recipient at the time it is opened
# and read. Do not match $QF_FILE in that case.
if ($match == 1 && $envelope_recipients != 0) {
print "Removing $QF_FILE...\n";
system "$qtool", "-d", $QF_FILE;
$messages_removed++;
}
}
}
print "$messages_removed total message(s) removed from mail queue.\n";
Queued mail by email address
The following Perl script will show all queued mail by email address. A message may be counted more than once if it has multiple envelope recipients.
#!/usr/bin/perl
use strict;
my $mqueue_directory = "/var/spool/mqueue";
my %occurrences;
use File::Find;
# Recursively find all files and directories in $mqueue_directory
find(\&wanted, $mqueue_directory);
sub wanted {
# Is this a qf* file?
if ( /^qf\w{14}/ ) {
open (QF_FILE, $_);
while(<QF_FILE>) {
# Lines beginning with R contain an envelope recipient
if ( /^R.*:<(.*)>$/ ) {
my $domain = lc($1);
# Add 1 to the %occurrences hash
$occurrences{$domain}++;
}
}
}
}
# Subroutine to sort hash by ascending value
sub hashValueAscendingNum {
$occurrences{$a} <=> $occurrences{$b};
}
# Print sorted results
foreach my $key (sort hashValueAscendingNum (keys(%occurrences))) {
print "$occurrences{$key} $key\n";
}
Removing mail by email address
The following Perl script will remove all mail in the mail queue addressed to email_address. Messages with multiple envelope recipients will not be deleted.
#!/usr/bin/perl
use strict;
# Exit immediately if email_address was not specified as command-line argument
if (!(defined($ARGV[0]))) {
(my $basename = $0) =~ s!^.*/!!;
print "Usage: $basename email_address\n";
exit 1;
}
# Convert email address supplied as command-line argument to lowercase
my $address_to_remove = lc($ARGV[0]);
my $qtool = "/usr/local/bin/qtool.pl";
my $mqueue_directory = "/var/spool/mqueue";
my $messages_removed = 0;
use File::Find;
# Recursively find all files and directories in $mqueue_directory
find(\&wanted, $mqueue_directory);
sub wanted {
# Is this a qf* file?
if ( /^qf\w{14}/ ) {
my $QF_FILE = $_;
my $envelope_recipients = 0;
my $match = 1;
open (QF_FILE, $_);
while(<QF_FILE>) {
# If any of the envelope recipients contain an email address other than
# $address_to_remove, do not match the message
if ( /^R.*:<(.*)>$/ ) {
my $recipient_address = lc($1);
$envelope_recipients++;
if ($recipient_address ne $address_to_remove) {
$match = 0;
last;
}
}
}
close (QF_FILE);
# $QF_FILE may not contain an envelope recipient at the time it is opened
# and read. Do not match $QF_FILE in that case.
if ($match == 1 && $envelope_recipients != 0) {
print "Removing $QF_FILE...\n";
system "$qtool", "-d", $QF_FILE;
$messages_removed++;
}
}
}
print "$messages_removed total message(s) removed from mail queue.\n";
Older notes
Note: the preferred method of queue removal is to use qtool.pl as illustrated above.
In order to remove mail from the queue, you have to delete the df* and qf* files from your mail queue directory, generally /var/spool/mqueue. The qf* file is the header of the message and the control file, and the df* file is the body of the message.
script to move undeliverable email in our /var/spool/mqueue mail queue to an alternate /tmp/mqueue directory.
#!/bin/sh
if [ -z $@ ] ; then
echo "Usage: $0 email_address"
exit 1
fi
for i in `(cd /var/spool/mqueue; grep -l "To:.*$1" qf* | cut -c3-)`
do
mv /var/spool/mqueue/*$i /tmp/mqueue
done
If you have multiple mail queues, such as q1, q2, q3, q4, and q5, you can use the following script:
#!/bin/sh
if [ -z $@ ] ; then
echo "Usage: $0 email_address"
exit 1
fi
for i in q1 q2 q3 q4 q5
do
for j in `(cd /var/spool/mqueue/$i; grep -l "To:.*$1" qf* | cut -c3-)`
do
mv /var/spool/mqueue/$i/*$j /tmp/mqueue
done
done
For example, running the script while passing the command-line argument badsender@baddomain.com will look for each qf* file in the mail queue containing To:.*badsender@baddomain.com. The regular
expression .* will match zero or more occurrences of any characters, numbers, or whitespace. For example, it would match:
To: badsender@baddomain.com
To: Bad Sender <badsender@baddomain.com>
The script then moves any other files (i.e. the body of the message) in the mail queue with the same Sendmail message ID to the alternate directory. It does this with the cut -c3- command, as the Sendmail message ID is the 3rd through the last character.
The mail is moved to /tmp/mqueue. If you are confident that you do not want the messages, you can delete them from this directory, or you could change the script to remove the files.
MRTG: Install and Configure in centOS
The Multi Router Traffic Grapher MRTG is a tool to monitor the traffic load on network-links.
MRTG generates HTML pages containing PNG images which provide a LIVE visual representation of this traffic. You need the following packages:
Requirements:
mrtg : Multi Router Traffic Grapher
net-snmp and net-snmp-utils : SNMP (Simple Network Management Protocol) is a protocol used for network management. The NET-SNMP project includes various SNMP tools. net-snmp package contains the snmpd and snmptrapd daemons, documentation, etc. Net-snmp-utils package
1:Install MRTG
Type the following command to install packages using yum command under CentOS / Fedora Linux:
# yum install mrtg net-snmp net-snmp-utils
2:Configure snmpd
If you need to monitor localhost including interface and other stuff such as CPU, memory etc, configure snmpd. Open /etc/snmp/snmpd.conf, enter:
# vi /etc/snmp/snmpd.conf
Update it as follows to only allow access from localhost:
com2sec local localhost public
group MyRWGroup v1 local
group MyRWGroup v2c local
group MyRWGroup usm local
view all included .1 80
access MyRWGroup "" any noauth exact all all none
syslocation Your_Location
syscontact Root <your@emailaddress.com>
Save and close the file.
# chkconfig snmpd on
# service snmpd restart
Make sure you see interface IP, by running the following command:
# snmpwalk -v 1 -c public localhost IP-MIB::ipAdEntIfIndex
Sample Outputs:
IP-MIB::ipAdEntIfIndex.123.xx.yy.zzz = INTEGER: 2
IP-MIB::ipAdEntIfIndex.127.0.0.1 = INTEGER: 1
3:Configure MRTG
Use cfgmaker command to creates /etc/mrtg/mrtg.cfg file.
# cfgmaker --global 'WorkDir: /var/www/mrtg' --output /etc/mrtg/mrtg.cfg public@localhost
--global 'WorkDir: /var/www/mrtg' : add global config entries i.e. set workdir to store MRTG graphs.
--output /etc/mrtg/mrtg.cfg: configr output filename
public@localhost: public is the community name and it is by default. Using the wrong community name you will give no response from the device. localhost is the DNS name or the IP number of an SNMP-managable device.
Finally, run indexmaker to create web pages which display the status of an array of mrtg interface status pages
# indexmaker --output=/var/www/mrtg/index.html /etc/mrtg/mrtg.cfg
4: Verify Cron Job
/etc/cron.d/mrtg runs mrtg command to monitor the traffic load on network links
# cat /etc/cron.d/mrtg
Sample Output
*/5 * * * * root LANG=C LC_ALL=C /usr/bin/mrtg /etc/mrtg/mrtg.cfg --lock-file /var/lock/mrtg/mrtg_l --confcache-file
/var/lib/mrtg/mrtg.ok
# chkconfig --list crond
If it is off in run level # 3, run the following to turn on crond service:
# chkconfig crond on
# service crond on
View mrtg graphs:
You need Apache web server to view graphs:
# yum install httpd
# chkconfig httpd on
# service httpd on
Go to a web browser and type
http://your-ip.add.ress/mrtg/
Mount partitions with ntfs file system with read/write access
If the rpmforge repo is disabled by default,
# yum --enablerepo=rpmforge install fuse fuse-ntfs-3g
For CentOS 6,
# yum install ntfs-3g
if you prefer to leave EPEL disabled by default
# yum --enablerepo epel install ntfs-3g
For Additional Functionality
# yum install ntfsprogs ntfsprogs-gnomevfs
Mounting NTFS Drives
# mkdir /mnt/drv1
# mkdir /mnt/drv2
# mkdir /mnt/drv3
Mounting with Read Only Access, add the line in /etc/fstab
/dev/sda1 /mnt/drv1 ntfs-3g ro,umask=0222,defaults 0 0
Mounting with Read Write Access, add the line in /etc/fstab
/dev/sda1 /mnt/drv1 ntfs-3g ro,umask=0222,defaults 0 0
/dev/sda1 /mnt/drv2 ntfs-3g ro,umask=0222,defaults 0 0
/dev/sda1 /mnt/drv3 ntfs-3g ro,umask=0222,defaults 0 0
# mount /mnt/drv1
# mount /mnt/drv2
# mount /mnt/drv3
Thats All, Enjoy Linux
# yum --enablerepo=rpmforge install fuse fuse-ntfs-3g
For CentOS 6,
# yum install ntfs-3g
if you prefer to leave EPEL disabled by default
# yum --enablerepo epel install ntfs-3g
For Additional Functionality
# yum install ntfsprogs ntfsprogs-gnomevfs
Mounting NTFS Drives
# mkdir /mnt/drv1
# mkdir /mnt/drv2
# mkdir /mnt/drv3
Mounting with Read Only Access, add the line in /etc/fstab
/dev/sda1 /mnt/drv1 ntfs-3g ro,umask=0222,defaults 0 0
Mounting with Read Write Access, add the line in /etc/fstab
/dev/sda1 /mnt/drv1 ntfs-3g ro,umask=0222,defaults 0 0
/dev/sda1 /mnt/drv2 ntfs-3g ro,umask=0222,defaults 0 0
/dev/sda1 /mnt/drv3 ntfs-3g ro,umask=0222,defaults 0 0
# mount /mnt/drv1
# mount /mnt/drv2
# mount /mnt/drv3
Thats All, Enjoy Linux
System Information Related Commands
Show architecture of machine
# arch
Show the timetable of 2007
# cal 2007
Show information CPU info
# cat /proc/cpuinfo
Show interrupts
# cat /proc/interrupts
Verify memory use
# cat /proc/meminfo
Show file(s) swap
# cat /proc/swaps
Show version of the kernel
# cat /proc/version
Show network adpters and statistics
# cat /proc/net/dev
Show mounted file system(s)
# cat /proc/mounts
Save date changes on BIOS
# clock -w
Show system date
# date
set date and time - MonthDayhoursMinutesYear.Seconds
# date 041217002007.00
Show hardware system components - (SMBIOS / DMI)
# dmidecode -q
Displays the characteristics of a hard-disk
# hdparm -i /dev/hda
Perform test reading on a hard-disk
# hdparm -tT /dev/sda
Display PCI devices
# lspci -tv
Show USB devices
# lsusb -tv
Show architecture of machine
# uname -m
Show used kernel version
# uname -r
# arch
Show the timetable of 2007
# cal 2007
Show information CPU info
# cat /proc/cpuinfo
Show interrupts
# cat /proc/interrupts
Verify memory use
# cat /proc/meminfo
Show file(s) swap
# cat /proc/swaps
Show version of the kernel
# cat /proc/version
Show network adpters and statistics
# cat /proc/net/dev
Show mounted file system(s)
# cat /proc/mounts
Save date changes on BIOS
# clock -w
Show system date
# date
set date and time - MonthDayhoursMinutesYear.Seconds
# date 041217002007.00
Show hardware system components - (SMBIOS / DMI)
# dmidecode -q
Displays the characteristics of a hard-disk
# hdparm -i /dev/hda
Perform test reading on a hard-disk
# hdparm -tT /dev/sda
Display PCI devices
# lspci -tv
Show USB devices
# lsusb -tv
Show architecture of machine
# uname -m
Show used kernel version
# uname -r
Archiving and Backup related commands
Decompress a file called 'file1.bz2'
# bunzip2 file1.bz2
Compress a file called 'file1'
# bzip2 file1
Decompress a file called 'file1.gz'
# gunzip file1.gz
Compress a file called 'file1'
# gzip file1
Compress with maximum compression
# gzip -9 file1
Create an archive rar called 'file1.rar'
# rar a file1.rar test_file
Compress 'file1', 'file2' and 'dir1' simultaneously
# rar a file1.rar file1 file2 dir1
Decompress rar archive
# rar x file1.rar
Create a uncompressed tarball
# tar -cvf archive.tar file1
Create an archive containing 'file1', 'file2' and 'dir1'
# tar -cvf archive.tar file1 file2 dir1
Show contents of an archive
# tar -tf archive.tar
Extract a tarball
# tar -xvf archive.tar
Extract a tarball into / tmp
# tar -xvf archive.tar -C /tmp
Create a tarball compressed into bzip2
# tar -cvfj archive.tar.bz2 dir1
Decompress a compressed tar archive in bzip2
# tar -xvfj archive.tar.bz2
Create a tarball compressed into gzip
# tar -cvfz archive.tar.gz dir1
Decompress a compressed tar archive in gzip
# tar -xvfz archive.tar.gz
Decompress rar archive
# unrar x file1.rar
Decompress a zip archive
# unzip file1.zip
Create an archive compressed in zip
# zip file1.zip file1
Compress in zip several files and directories simultaneously
# zip -r file1.zip file1 file2 dir1
Hard Disk related commands in Linux
Checking Disk capacity, Partition tables, etc.
[root@server ~]# fdisk -l
Get Detailed/current information directly from hard drive
[root@server ~]# hdparm -I /dev/sda
Check available/used/free spaces in each partitions
[root@server ~]# df -h
Check Hard drive speeds
[root@server ~]# hdparm -Tt /dev/sda
To list the partition tables for the specified devices
#fdisk -l
Pass print option to displays the partition table
#parted /dev/sda print
To display all disks and storage controllers in the system
#lshw -class disk -class storage
Find Out Disks Name Only
#lshw -short -C disk
The smartctl command act as a control and monitor Utility for SMART disks under Linux and Unix like operating systems
#smartctl -d ata -a -i /dev/sda
Partition the new disk using fdisk command
#fdisk -l | grep '^Disk'
Format the new disk using mkfs.ext3 command
#mkfs.ext3 /dev/sdb1
Mount the new disk using mount command
#mkdir /disk1
#mount /dev/sdb1 /disk1
#df -H
Label the partition
#e2label /dev/sdb1 /backup
Checking the Hard Disk for errors
#fsck.file_system_type, E.g #fsck.ext3
Show list of partitions mounted
# df -h [man]
show the used space by installed deb packages, sorting by size
#dpkg-query -W -f='${Installed-Size;10}t${Package}n' | sort -k1,1n
Estimate space used by directory 'dir1'
#du -sh dir1
Show size of the files and directories sorted by size
#du -sk * | sort -rn
Show size of the files and directories ordered by size
#ls -lSr |more
Show space used by rpm packages installed sorted by size
# rpm -q -a --qf '%10{SIZE}t%{NAME}n' | sort -k1,1n
Format a floppy disk
# fdformat -n /dev/fd0
Create a filesystem type linux ext2 on hda1 partition
# mke2fs /dev/hda1
Create a filesystem type linux ext3 on hda1 partition
# mke2fs -j /dev/hda1
Create a filesystem type linux on hda1 partition
# mkfs /dev/hda1
Create a FAT32 filesystem
# mkfs -t vfat 32 -F /dev/hda1
Create a swap filesystem
# mkswap /dev/hda3
Force umount when the device is busy
# fuser -km /mnt/hda2
Mount disk called hda2 - verify existence of the directory '/ mnt/hda2'
# mount /dev/hda2 /mnt/hda2
Mount a floppy disk
# mount /dev/fd0 /mnt/floppy
Mount a cdrom / dvdrom
# mount /dev/cdrom /mnt/cdrom
Mount a cdrw / dvdrom
# mount /dev/hdc /mnt/cdrecorder
Mount a cdrw / dvdrom [man]
# mount /dev/hdb /mnt/cdrecorder
Mount a file or iso image
# mount -o loop file.iso /mnt/cdrom
Mount a Windows FAT32 file system
# mount -t vfat /dev/hda5 /mnt/hda5
Mount a usb pen-drive or flash-drive
# mount /dev/sda1 /mnt/usbdisk
Mount a windows network share
# mount -t smbfs -o username=user,password=pass //WinClient/share /mnt/share
Unmount disk called hda2 - exit from mount point '/ mnt/hda2' first
# umount /dev/hda2
Run umount without writing the file /etc/mtab - useful when the file is read-only or the hard disk is full
# umount -n /mnt/hda2
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