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Sat, Jul 25, 2015 10:49 pm

Compiling Apache from source files on a CentOS 7 system

I needed to build Apache from an SRPM file, since I needed to change options for suexec and recompile it. I downloaded the httpd source code, i.e., the "source RPM", httpd-2.4.6-19.el7.centos.src.rpm, from the CentOS Mirror site. But when I attempted to rebuild Apache, I encountered the error message "configure: error: APR not found. Please read the documentation." When I got past that error message I saw the error message "configure: error: pcre-config for libpcre not found. PCRE is required and available from http://pcre.org/". I was able to get past those issues, but the process of recompiling suexec wasn't as quick as I had hoped it would be.

[ More Info ]

[/os/unix/linux/centos] permanent link

Fri, Jul 24, 2015 10:06 pm

Using diskutil to obtain disk drive info on OS X

To obtain information on the disk drives attached to a Mac OS X system, including the Self-Monitoring, Analysis and Reporting Technology (S.M.A.R.T), aka SMART, status of drives. you can use the diskutil list command, which will show all of the disk drives attached to the system.

Pams-Computer:~ pam$ diskutil list
/dev/disk0
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *250.1 GB   disk0
   1:                        EFI                         209.7 MB   disk0s1
   2:                  Apple_HFS Macintosh HD            249.7 GB   disk0s2
/dev/disk1
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:     FDisk_partition_scheme                        *8.0 GB     disk1
   1:                 DOS_FAT_32 SI_IMPRESS              8.0 GB     disk1s1
Pams-Computer:~ pam$

[ More Info ]

[/os/os-x] permanent link

Wed, Jul 22, 2015 6:20 pm

Bopup Scanner

If you need to determine which IP address on your LAN are in use and the media access control (MAC) address associated with them, Bopup Scanner from B Labs is a handy free utility that will quickly scan a range of IP addresses and provide the MAC addresses for the systems within the specified IP address range. It can also tell you if any of the systems are functioning as web servers listening on TCP ports 80 or 8080.

[ More Info ]

[/network/tools/scanning/bopupscanner] permanent link

Sun, Jul 19, 2015 9:57 pm

Configuring a Custom Service from the CLI on a NetScreen Firewall

If you need to configure a custom service from the command line interface (CLI) you obtain by a Secure Shell (SSH) connection to a Juniper NetScreen Firewall running ScreenOS, you can use the set service command. E.g., to create a custom service for an SSH server listening on a non-standard port for SSH, you could use something like the following, if the server is listening on port 2005:

set service "Auburn SSH" protocol tcp src-port 1024-65535 dst-port 2005-2005

The text in quotation marks immediately after set service is just a descriptive name you can give to the service to make the purpose of the custom service more immediately identifiable.

If you have not yet created an address book entry for the system running the custom service, you can use the set address command to create it.

[ More Info ]

[/security/firewalls/netscreen] permanent link

Fri, Jul 17, 2015 10:52 pm

Managing database access with MariaDB or MySQL

Database access for MariaDB or MySQL database users can be controlled through the GRANT, REVOKE and DROP commands. You can see a list of the users with the select user from mysql.user; command. If you add host to that command, e.g., SELECT user, host from mysql.user;, you can also see the hosts/IP addresses from which users are allowed to connect to databases.

[ More Info ]

[/software/database/mysql] permanent link

Thu, Jul 16, 2015 11:19 pm

Speed of spinning disk drives

A hard disk drive in a computer today will normally be a 3.5 inch or 2.5 inch drive, which is the size of the platters on which data is stored inside drives. Read/write heads move over the spinning platters to read and record data. Laptops will have a 2.5" drive and desktop systems will likely have a 3.5" drive, though may have a 2.5" drive. Before these sizes became common, there were 5.25" drives when Parallel ATA (PATA) drives were used. Seagate released the first 5.25" drive in 1980 and Rodime released the first 3.5" hard drive in 19831. Before 5.25" inch drives were used in desktop systems there were 8" drives. You can find some of the history of hard drive development in the Wikipedia article History of hard disk drives and the PCWorld article by Rex Farrance, Timeline: 50 Years of Hard Drives.

Hard disk drives have spinning platters within them, much as an old record player will spin a record, though the platter in a HDD spins much faster. Today you may find drives that spin at 5,200 revolutions per minute (RPM) or 7,200 revolutions per minute (RPM). What does that equate to in miles per hour (MPH)?

If a platter in the HDD is 3.5" in diameter then the radius is 1/2 that number, i.e. 1.75". A platter in a 2.5" drive has a radius of 1.25". The circumference of a circle is 2πr, i.e., 2 times the radius times the mathematical constant pi, which is approximately 3.14159265. So for a point on the outer edge of a 3.5" drive's platter that is spinning at 7200 RPM where a point on the outer edge of the platter travels 2 * π * r inches per revolution, the speed in MPH is approximately 75 MPH:

2 * 3.14 * 1.75 in/rev * 7200 rev/min * 60 minutes/hour / 12 inch/foot / 5280 foot/mile

For a 2" drive, the speed is approximately 53.5 MPH:

2 * 3.14 * 1.25 * 7200 * 60 / 12 / 5280

In kilometers per hour, those numbers equate to 120.7 kph for the 3.5" disk drive and and 86 kph for the 2.5" drive.

If a drive is spinning at the slower 5400 RPM, then the speed in MPH for a 3.5" drive is approximately 28 MPH (45 kph):

3.14 * 1.75 * 5400 * 60 / 12 / 5280 ≈ 28

For a 2.5" drive it is approximately 20 MPH (32 kph):

3.14 * 1.25 * 5400 * 60 / 12 / 5280 ≈ 20

References:

  1. Timeline: 50 Years of Hard Drives
    By: Rex Farrance
    PCWorld
  2. History of hard disk drives
    Wikipedia, The Free Encyclopedia

[/info/pc/hdd] permanent link

Tue, Jul 14, 2015 10:40 pm

Screencapture command on Os X

You can take a screen shot from a command line interface (CLI) on a Mac OS X system by using the screencapture command. The screen capture program is located in /usr/sbin. You can see the available options by using screencapture -h; the -h option isn't a valid option for the application, but it will cause the app to print the options it does accept.

$ which screencapture
/usr/sbin/screencapture
$ screencapture -h
screencapture: illegal option -- h
usage: screencapture [-icMPmwsWxSCUtoa] [files]
  -c         force screen capture to go to the clipboard
  -C         capture the cursor as well as the screen. only in non-interactive modes
  -d         display errors to the user graphically
  -i         capture screen interactively, by selection or window
               control key - causes screen shot to go to clipboard
               space key   - toggle between mouse selection and
                             window selection modes
               escape key  - cancels interactive screen shot
  -m         only capture the main monitor, undefined if -i is set
  -M         screen capture output will go to a new Mail message
  -o         in window capture mode, do not capture the shadow of the window
  -P         screen capture output will open in Preview
  -s         only allow mouse selection mode
  -S         in window capture mode, capture the screen not the window
  -t<format> image format to create, default is png (other options include pdf, jpg, tiff and other formats)
  -T<seconds> Take the picture after a delay of <seconds>, default is 5
  -w         only allow window selection mode
  -W         start interaction in window selection mode
  -x         do not play sounds
  -a         do not include windows attached to selected windows
  -r         do not add dpi meta data to image
  -l<windowid> capture this windowsid
  -R<x,y,w,h> capture screen rect
  files   where to save the screen capture, 1 file per screen
$

By default, a screenshot will be stored in PNG format, but you can select other formats with the -t (lowercase "t") option. You can specify that you want to use PDF, JPG, or TIFF, instead. You can use the -T (uppercase "T") option to specify a delay in seconds between the time the command is issued and the time the screen shot is taken, which gives you the opportunity to switch to another window to have a screenshot taken of it. The advantage of screenshot over the GUI Preview program found in the Applications folder for taking a picture of a window is that with Preview sometimes pulldown menus will disappear from a window when you switch to Preview to take a screen shot. With screencapture, you can issue the command with a delay, the default is 5 seconds, switch to the relevant window, select the menu or other option, and then wait the number of seconds specified for screencapture to capture the contents appearing in that window at that time. E.g., the command below will wait 10 seconds to take a snapshot of what is appearing on a window that is the current one when 10 seconds elapses.

$ screencapture -T 10 grayed.png
libpng warning: zero length keyword
libpng warning: Empty language field in iTXt chunk
$

You won't see any indication that the screen capture occurred, so you need to just wait until the specified time has elapsed before looking for the output file, which will be placed in the current directory from which you issued the command if you didn't specify a path, but only the file name. The "libpng warnings" don't indicate that the screen shot couldn't be taken; the output file specified is a valild PNG file.

[/os/os-x] permanent link

Mon, Jul 13, 2015 10:49 pm

ChromeCacheView - Cache viewer for Google Chrome Web browser

I recently overwrote a file with notes about a problem I had to deal with that was residing on a web server by moving another file over top of it accidentally. I was in a hurry to complete my notes so I could go to bed; I thought about waiting until the morning to complete the notes, but thoughit I could complete them in just a few more minutes, but when I used !:1 as a shorthand in a mv command, I didn't realize that the second item on the last command line entry was the filename for the file with my notes. I didn't realize what I had done until I tried to view the web page with my notes from the PC I was using at the time for the SSH connection to the web server.

Since I had viewed the notes in the Google Chrome browser on the Microsoft Windows-based system I was on shortly before I overwrote them, I thought I might be able to find a copy of the notes in the browser's cache. But since I didn't grasp what I had done until I refreshed the page in the browser, it was now too late to get the data from the Chrome cache, since the cached page now just showed the "404 file not found" message due to the file no longer existing on the web server. So I thought there still might be a slim chance that I could recover the notes web page from a Volume Shadow Copy, i.e., a prior version of the file stored on the Windows system. I thought, if I could identify the particular cache file used for that webpage, there might be a prior version of that file stored by the Volume Shadow Copy Service. I thought I could possibly use ChromeCacheView, which is a small, free program that will allow you to examine the Google Chrome web browser cache. With that program you can view a list of all cached web pages and view the cached copies of those pages stored on the system. I was able to identify the particular file in the C:\Users\%username%\AppData\Local\Google\Chrome\User Data\Default\Cache directory that held that particular cached webpage. The file was data_4, but unfortunately, I wasn't able to find a prior version of the file. Though if you need to examine the Chrome cache on a Microsoft Windows system, ChromeCacheView is a very useful tool well-suited to that purpose. You can also put chrome://cache in the Chrome addres bar to see a list of URLs of cached pages, but ChromeCacheView provides many more capabilities for operations on that list of cached items.

[/network/web/browser/chrome] permanent link

Sun, Jul 12, 2015 9:04 pm

Resetting the admin password for an SMF Forum

I needed to reset a forgotten administrator password for a Simple Machines Forum (SMF) forum running SMF 2.0.10 today. To do so, since phpMyAdmin was installed on the server hosting the forum, I used phpMyAdmin to access the database for the forum and then found the entry in the _members table for the administrator account. I saw the following fields for the password (actual values not shown):
ColumnTypeFunctionNullValue
passwordvarchar(64)   d2d0b6f8f5e59d26550054b2f08bc7ceb514992b
password_saltvarchar(255)   f284

I replaced the value in the password field with a new password and deleted the contents of the password_salt field and then clicked on the Go button to update the record in the table for the administrator account.

After I logged into the forum with the administrator account, I checked the record in the table in the database for the forum again and found that there was a new value in the passwd_salt field and the entry in the password field was re-encrypted and was now a long sequence of digits and characters again rather than the plain text password I entered

A password salt is "random data that is used as an additional input to a one-way function that hashes a password or passphrase. The primary function of salts is to defend against dictionary attacks versus a list of password hashes and against pre-computed rainbow table attacks." By not storing a password in a database in plain text, even if someone gains unauthorized access to the database, even if they can then view passwords stored in the database, they can't see the actual password used for the account associated with the password. If the password was simply stored in an encrypted form, if the attacker who gained access to the database had access to a "rainbow table", i.e., a table that matched the plain text version of a password with its encrypted form, he could deduce the orginal password. But by using a random "salt" value as part of the encrypted password generation, a rainbow table won't help the attacker, since even if Sam and Sally both use the same password and the same encryption function is used to generate the stored password for both of them, because the random salt value is used as part of the process to obtain the encrypted version of the password, the value stored in the password for Sally wil not match that for Sam. So an attacker can't look up an encrypted entry in a rainbow table and find a match for the unencrypted password used to create the encrypted version and won't even know that Sam and Sally have the same password. This helps protect Sam and Sally, even if all of their data on the site where the database is stored is compromised, since the malefactor doesn't get a password for them that they might have used on other sites as well.

References:

  1. I accidentally lost my admin account! What can I do? - Online Manual
    SMF Online Manual

[/network/web/forums/smf] permanent link

Sat, Jul 11, 2015 10:58 pm

Restoring home and start pages in Chrome after installing Yahoo Messenger

After my wife installed the Yahoo Messenger Suite so that she could chat with a friend using it, on opening the Google Chrome browser, the Yahoo Search - Web Search page would appear. She didn't want that; she wanted to have google.com as her home page and to have a tab open to that when she started the browser as had occurred prior the the installation of the Yahoo Messenger software. She said she had chosen not to install the Yahoo toolbar and not to have it make such changes when she installed the software, so was irked to find her home page was "hijacked" to be a Yahoo search page. I found that I need to change both her home page and the start page for Chrome to put her settings back to what they had been prior to the installtion of the software.

[ More Info ]

[/network/web/browser/chrome] permanent link

Fri, Jul 10, 2015 11:12 pm

Recovery of Corrupted QuickBooks File

I received a call today from someone who reported that she had started compressing a QuickBooks file, since she wanted to upload the data to Intuit's site (QuickBooks 2013 provides a "condense" function that is accessible from the File menu by choosing Utilities then Condense data), but during the process of removing old entries from many years ago the company owner needed her to do some work in QuickBooks so she terminated the compression operation. As soon as she told me that I suspected she was calling because by doing so the company file had been corrupted. That seemed to be the case, because she said she could no longer find any entries in the file for this year besides those for today. She thought that the QuickBooks data was being backed up to an external, USB-attached disk drive on her system, but when I checked its contents I found that the last backup to that drive had occurred a couple of years ago.

Fortunately the data was stored on a Microsoft Windows system running a version of Windows that uses Microsoft's Volume Snapshot Service , which allows you to simply right-click on a file or folder name, choose Properties and then click on the Previous Versions tab and select from shadow copies of the file or folder that were made previously, though in this case I didn't even need to do that.

[ More Info ]

[/financial] permanent link

Fri, Jul 10, 2015 12:29 pm

Using wmic to get disk drive information

If you want to obtain information on the internal and external drives attached to a Microsoft windows system from a command line prompt, you can use the wmic command. To view just the model number for drives, you can use wmic diskdrive get model.
c:\>wmic diskdrive get Model
Model
ST31000528AS
ST6000DX000-1H217Z
Generic- Multi-Card USB Device
WD My Book 1230 USB Device


c:\>

You can also use wmic diskdrive get Name, Manufacturer, Model to get the name of the drive in the system and manufacturer, though for the manufacturer you may just see (Standard disk drives). Though, if you have a model number, such as ST31000528AS, you can often deduce the manufacturer without even doing an online search on the model number. E.g., Seagate starts model numbers with "ST", so I know that the ST31000528AS and ST6000DX000-1H217Z are Seagate drives. And I know the "WD" in "WD My Book 1230 USB Device" means the drive is a Western Digital external disk drive.

You can also obtain the capacity of each drive in bytes by using the size parameter.

c:\>wmic diskdrive get model, size
Model                           Size
ST31000528AS                    1000202273280
ST6000DX000-1H217Z              6001172513280
Generic- Multi-Card USB Device
WD My Book 1230 USB Device      4000710389760


c:\>

So the ST31000528AS drive is 4000710389760 byte / 1,000 byte/kilobyte / 1,000 kilobyte/megabyte / 1,000 megabyte/gigabyte / 1,000 gigabyte/terrabyte = 4 TB using the 1,000 number used by manufacturers rather than the 1,024 byte/kilobyte, etc. number often used in computing. E.g., see the Wikipedia article on Gigabyte.

If you want to see the list of other drive parameters you can check, use wmic diskdrive get /?.

c:\>wmic diskdrive get /?

Property get operations.
USAGE:

GET [<property list>] [<get switches>]
NOTE: <property list> ::= <property name> | <property name>,  <property list>

The following properties are available:
Property                                Type                    Operation
========                                ====                    =========
Availability                            N/A                     N/A
BytesPerSector                          N/A                     N/A
Capabilities                            N/A                     N/A
CapabilityDescriptions                  N/A                     N/A
CompressionMethod                       N/A                     N/A
ConfigManagerErrorCode                  N/A                     N/A
ConfigManagerUserConfig                 N/A                     N/A
DefaultBlockSize                        N/A                     N/A
Description                             N/A                     N/A
DeviceID                                N/A                     N/A
ErrorCleared                            N/A                     N/A
ErrorDescription                        N/A                     N/A
ErrorMethodology                        N/A                     N/A
Index                                   N/A                     N/A
InstallDate                             N/A                     N/A
InterfaceType                           N/A                     N/A
LastErrorCode                           N/A                     N/A
Manufacturer                            N/A                     N/A
MaxBlockSize                            N/A                     N/A
MaxMediaSize                            N/A                     N/A
MediaLoaded                             N/A                     N/A
MediaType                               N/A                     N/A
MinBlockSize                            N/A                     N/A
Model                                   N/A                     N/A
Name                                    N/A                     N/A
NeedsCleaning                           N/A                     N/A
NumberOfMediaSupported                  N/A                     N/A
PNPDeviceID                             N/A                     N/A
Partitions                              N/A                     N/A
PowerManagementCapabilities             N/A                     N/A
PowerManagementSupported                N/A                     N/A
SCSIBus                                 N/A                     N/A
SCSILogicalUnit                         N/A                     N/A
SCSIPort                                N/A                     N/A
SCSITargetId                            N/A                     N/A
SectorsPerTrack                         N/A                     N/A
Signature                               N/A                     N/A
Size                                    N/A                     N/A
Status                                  N/A                     N/A
StatusInfo                              N/A                     N/A
SystemName                              N/A                     N/A
TotalCylinders                          N/A                     N/A
TotalHeads                              N/A                     N/A
TotalSectors                            N/A                     N/A
TotalTracks                             N/A                     N/A
TracksPerCylinder                       N/A                     N/A

The following GET switches are available:

/VALUE                       - Return value.
/ALL(default)                - Return the data and metadata for the attribute.
/TRANSLATE:<table name>      - Translate output via values from <table name>.
/EVERY:<interval> [/REPEAT:<repeat count>] - Returns value every (X interval) se
conds, If /REPEAT specified the command is executed <repeat count> times.
/FORMAT:<format specifier>   - Keyword/XSL filename to process the XML results.

NOTE: Order of /TRANSLATE and /FORMAT switches influences the appearance of outp
ut.
Case1: If /TRANSLATE precedes /FORMAT, then translation of results will be follo
wed by formatting.
Case2: If /TRANSLATE succeeds /FORMAT, then translation of the formatted results
 will be done.

[/os/windows/commands/wmic] permanent link

Fri, Jul 10, 2015 12:23 pm

Windows Versions System Requirements

The hardware requirements Microsoft lists for various versions of its operating systems has remained the same for processor speed and memory from Windows Vista through Windows 7, 8, and 8.1. Microsoft recommends a 1 GHz or faster Central Processing Unit (CPU) and 1 gigabyte (GB) of system memory. And from Windows 7 through Windows 8.1 the amount of available hard drive space recommended has been 16 GB available hard disk space for the 32-bit version or or 20 GB for the 64-bit version.

[ More Info ]

[/os/windows] permanent link

Wed, Jul 08, 2015 11:39 pm

Plaintext authentication disallowed on non-secure (SSL/TLS) connections

Someone reported to me recently that she could no longer check her email. She was using Outlook and kept getting prompted to provide the password, but when she provided it Outlook wasn't able to check her incoming email and she would be prompted for the password again.

She told me the password she was using, so I established a telnet connection to port 110, the Post Office Protocol version 3 (POP3) port from another system using PuTTY and entered her userid and password. The email server, which uses Dovecot to provide IMAP and POP3 service, acknowledged that was the correct password.

+OK [XCLIENT] Dovecot ready.
user nell
-ERR Unknown command.
user nell
+OK
pass Rugs1234
+OK Logged in.
stat
+OK 52 483564
quit

If you connect to port 110, the pop3 port, you can enter a user command to provide the userid (I don't know why dovecot always responded to the first submission of that command with -ERR Unknown command, when I used PuTTY to connect, but then accepted it on the second submission) and then a pass command followed by the password. You can then issue a stat or uidl command to check on the number of messages in the inbox and their size. For the stat command, the first number in the response is the number of messages and the second number is their size in bytes. The uidl command shows the unique message id for each message. You can end the session with the quit command.

Since the password seemed to be correct, I had her try again to download her email while I observed what was happening with tcpdump on the mail server by issing the command tcpdump -i enp1s4 'port 110' -A from the root account. I used i enp1s4, because enp1s4 is the network interface on that particular system. The -A at the end instructs tcpdump to print each packet (minus its link level header) in ASCII.

What I observed was her system sending the USER command and her userid. But then Outlook on her system would send the AUTH command and the server would reply ".-ERR [AUTH] Plaintext authentication disallowed on non-secure (SSL/TLS) connections"

10:29:34.219018 IP 10-45-1-012-dhcp.gsv.md.example.com.50990 > 

localhost.localdomain.pop3: Flags [P.], seq 8:19, ack 29, win 16418, length 11
E..3!.@.{...H-.H.......n.....(."P.@"....USER nell

10:29:34.219182 IP localhost.localdomain.pop3 > 10-45-1-012- 
dhcp.gsv.md.example.com.50990: Flags [P.], seq 29:115, ack 19, win 115, length 86
...-ERR [AUTH] Plaintext authentication disallowed on non-secure (SSL/TLS) connections.

The AUTH command indicates an authentication mechanism to the server as noted in Request for Comments (RFC) 1734 POP3 AUTHentication command. RFCs are the mechanism for defining Internet standards.

When I observed what was happening with the same tcpdump command when I connected to the server from another system on its LAN by a telnet connection to port 110, I saw the following:

# tcpdump -i enp1s4 'port 110' -A

10:27:30.475105 IP 192.168.0.6.63448 > localhost.localdomain.pop3: Flags [P.], seq 67:76, 

ack 120, win 256, length 9
E..1.1@...r;...........n......Q.P.......user nell
10:27:30.475211 IP 192.168.0.6.63448 > localhost.localdomain.pop3: Flags [P.], seq 76:78, 

ack 120, win 256, length 2
E..*.2@...rA...........n......Q.P...n...
....
10:27:30.475264 IP localhost.localdomain.pop3 > 192.168.0.6.63448: Flags [.], ack 78, win 

115, length 0
E..(g.@.@.N..........n....Q.....P..s.u..
10:27:30.475319 IP localhost.localdomain.pop3 > 192.168.0.6.63448: Flags [P.], seq 

120:125, ack 78, win 115, length 5
E..-g.@.@.N..........n....Q.....P..s.z..+OK

10:27:30.534264 IP 192.168.0.6.63448 > localhost.localdomain.pop3: Flags [.], ack 125, win 

256, length 0
E..(.6@...r?...........n......Q.P...{.........
10:27:36.602821 IP 192.168.0.6.63448 > localhost.localdomain.pop3: Flags [P.], seq 78:91, 

ack 125, win 256, length 13
E..5.E@...r#...........n......Q.P.../...pass Rugs1234
10:27:36.602938 IP 192.168.0.6.63448 > localhost.localdomain.pop3: Flags [P.], seq 91:93, 

ack 125, win 256, length 2
E..*.F@...r-...........n......Q.P...n...
....
10:27:36.603007 IP localhost.localdomain.pop3 > 192.168.0.6.63448: Flags [.], ack 93, win 

115, length 0
E..(g.@.@.N..........n....Q.....P..s.u..
10:27:36.735972 IP localhost.localdomain.pop3 > 192.168.0.6.63448: Flags [P.], seq 

125:141, ack 93, win 115, length 16
E..8g.@.@.N..........n....Q.....P..s....+OK Logged in.

I.e., the server was accepting a plaintext password, though it wasn't accepting one from her system. When I entered the AUTH command from the telnet session to port 110, it was accepted without that error message.

+OK [XCLIENT] Dovecot ready.
user nell
-ERR Unknown command.
user nell
+OK
AUTH
+OK
PLAIN
.
pass Rugs1234
+OK Logged in.

I then remembered that she had told me her ISP replaced her network equipment recently. She has an IP that remains constant unless the router is replaced at her end in which case the new device has a different media access control (MAC) address and will be assigned a different IP address.

I put the new IP address in the /etc/mail/access file, so that sendmail would allow relaying from that IP address without any authentication. I.e., I added a line with her IP address followed by RELAY.

10.45.1.12                              RELAY

I then ran the makemap hash command to generate a new /etc/mail/access.db file.

# makemap hash /etc/mail/access </etc/mail/access

But that only allowed her to send email via sendmail without authentication. I also had to update dovecot's configuration file at /etc/dovecot/dovecot.conf and change the IP address there for her system so that she could use plaintext authentication, i.e., an unencrypted password (I need to go to her location and change the Outlook configuration there to use other than plaintext authentication). I didn't recall that change was needed until finding a note I had made previously regarding dovecot's logon_trusted_networks setting.

The relevant section of the dovecot.conf file is shown below for cases where plaintext authentication is being allowed.

# Space separated list of trusted network ranges. Connections from these
# IPs are allowed to override their IP addresses and ports (for logging and
# for authentication checks). disable_plaintext_auth is also ignored for
# these networks. Typically you'd specify your IMAP proxy servers here.
login_trusted_networks = 192.168.0.0/24 192.168.7.0/24 10.45.1.12

In this case dovecot was configured to allow plaintext logins from two 192.68 subnets and her specific IP address. But since her IP address had changed to a new one, dovecot was no longer permitting plaintext authentication from her system. After changing the login_trusted_networks line to match her particular IP address, I restarted dovecot.

# service dovecot restart
Redirecting to /bin/systemctl restart  dovecot.service

When I had her try again, she was then able to download her email.

Note: IP addresses, userid, and password are, of course, not the actual ones used.

[/network/email/dovecot] permanent link

Tue, Jul 07, 2015 11:33 pm

Setting up Time Machine and backing up an OS X system

Mac OS X systems come with a backup program named Time Machine, which can be found in the Applications folder. If you attach an external drive to the system and configure Time Machine to use it, the program will backup the system automatically and maintain the following backups:

The app will delete the oldest backups when the backup drive becomes full.

[ More Info ]

[/os/os-x/Time_Machine] permanent link

Mon, Jul 06, 2015 10:53 pm

Juniper NetScreen SNMP Information

Juniper NetScreen Firewalls running the ScreenOS operating system, including older models, such as a Netscreen-5GT firewall, can be configured for Simple Network Management Protocol (SNMP) support to monitor bandwidth utilization, etc. SNMP information can be viewed or configured through the web-based interface or via the command line interface (CLI) using get snmp, set snmp and unset snmp commands.

[ More Info ]

[/security/firewalls/netscreen] permanent link

Sun, Jul 05, 2015 9:55 pm

Testing access to a website using PuTTY

Microsoft doesn't provide a telnet program with its current operating systems by default, but a commonly used program for telnet and SSH on Microsoft Windows systems is PuTTY which is free. A telnet client is provided with many Linux distributions and one is available with Apple's OS X operating system. PuTTY is also available for Unix/Linux systems. E.g., see How To Install & use Putty in Ubuntu Linux written by Pradeep Kumar on July 13, 2014.

With a telnet program you can send commands/headers to a web server to emulate those that a browser would send to a web server and observe the responses from the server. This can be useful in some troubleshooting efforts. E.g, see Testing acces to a website using PuTTY for how to configure PuTTY on a Microsoft Windows system to perform a basic connectivity test to port 80 and request a web page for a particular site from the server.

[/network/web/server] permanent link

Sat, Jul 04, 2015 12:56 pm

Chrome Memory Usage under Windows

Oftentimes I've found that a web browser is responsible for high memory utilization or high CPU usage on a system. But determing what tab or tabs is culpable can be difficult. Fortunately, Google provides a mechanism for doing so within its Chrome browser. By putting chrome://memory in the address bar in a tab within the browser, you can get details on the total memory usage by all browsers open on the system and the memory consumed by tabs within Chrome.

[ More Info ]

[/network/web/browser/chrome] permanent link

Fri, Jul 03, 2015 7:53 pm

Partitioning and formatting a drive with Clonezilla

Clonezilla, which is a live CD based on Debian Linux, provides the capability to clone one disk drive to another. You can boot a system from the live CD and make an image copy of one drive to another. Alternatively, you can store an image of an entire drive or partitions on a drive in files on another drive. If the drive to be used for the backup is not already partitioned and formatted, you can obtain a command prompt and use the fdisk command to partition the drive and mkfs.ext3 to format the drive.

[ More Info ]

[/os/unix/linux/Clonezilla] permanent link

Thu, Jul 02, 2015 11:01 pm

OS X Wireless Diagnostics

On a Mac OS X system, at the bottom of the display you see when you hold down the Option key while clicking on the icon for wireless networking, you will see "Open Wireless Diagnostics"; select that option to start the wireless networking diagnostics program provided by Apple. The utility can be used for troubleshooting Wi-Fi network problems and to generate a report of information related to wireless networking on the system, which may assist you with troubleshooting Wi-Fi issues on the system.

[ More Info ]

[/os/os-x/wireless] permanent link

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