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Tue, Mar 28, 2017 9:39 pm

Determining which packages were recently installed on a CentOS Linux system

I needed to determine which packages were recently installed on a CentOS 7 system where yum is used to install packages. The command rpm -qa --last will list all packages that have been installed in chronological order with the most recently installed packages listed first, since the --last option orders the package listing by install time such that the latest packages are at the top. E.g.:

# rpm -qa --last
amarok-utils-2.8.0-19.el7.x86_64              Fri 12 Aug 2016 09:02:34 PM EDT
amarok-libs-2.8.0-19.el7.x86_64               Fri 12 Aug 2016 09:02:34 PM EDT
amarok-2.8.0-19.el7.x86_64                    Fri 12 Aug 2016 09:02:31 PM EDT
taglib-extras-1.0.1-8.el7.x86_64              Fri 12 Aug 2016 09:02:17 PM EDT
mariadb-embedded-5.5.50-1.el7_2.x86_64        Fri 12 Aug 2016 09:02:17 PM EDT
qjson-0.8.1-4.el7.x86_64                      Fri 12 Aug 2016 09:02:15 PM EDT
kdelibs-webkit-4.14.8-1.el7.x86_64            Fri 12 Aug 2016 09:02:14 PM EDT
qtscriptbindings-0.2.0-5.el7.x86_64           Fri 12 Aug 2016 09:02:13 PM EDT
qtwebkit-2.3.4-6.el7.x86_64                   Fri 12 Aug 2016 09:01:57 PM EDT
alpine-2.20-2.el7.x86_64                      Mon 08 Aug 2016 10:13:54 PM EDT
fuse-sshfs-2.5-1.el7.x86_64                   Mon 08 Aug 2016 09:28:26 PM EDT
gpg-pubkey-352c64e5-52ae6884                  Mon 08 Aug 2016 09:27:13 PM EDT
epel-release-7-6.noarch                       Mon 08 Aug 2016 09:12:51 PM EDT
lynx-2.8.8-0.3.dev15.el7.x86_64               Fri 05 Aug 2016 10:28:17 PM EDT
telnet-0.17-59.el7.x86_64                     Sat 30 Jul 2016 04:34:17 PM EDT
thunderbird-45.2-1.el7.centos.x86_64          Sat 30 Jul 2016 04:10:55 PM EDT
mutt-1.5.21-26.el7.x86_64                     Sat 30 Jul 2016 03:50:58 PM EDT
<text snipped>
gnu-free-fonts-common-20120503-8.el7.noarch   Fri 15 Jul 2016 03:10:39 PM EDT
dejavu-fonts-common-2.33-6.el7.noarch         Fri 15 Jul 2016 03:10:39 PM EDT
libgcc-4.8.5-4.el7.x86_64                     Fri 15 Jul 2016 03:10:38 PM EDT
fontpackages-filesystem-1.44-8.el7.noarch     Fri 15 Jul 2016 03:10:38 PM EDT
control-center-filesystem-3.14.5-8.el7.x86_64 Fri 15 Jul 2016 03:10:38 PM EDT

[ More Info ]

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

Sun, Mar 26, 2017 5:10 pm

Unrar for Centos 7

I needed to convert a rar file to a zip file on a CentOS 7 Linux system. But when I tried installing an unrar package with yum, the package manager on the system, I found none was available from any of the software repositories the system was configured to check for packages.

# yum install unrar
Loaded plugins: fastestmirror, langpacks
Loading mirror speeds from cached hostfile
 * base:
 * epel:
 * extras:
 * updates:
No package unrar available.
Error: Nothing to do
# yum install rar
Loaded plugins: fastestmirror, langpacks
Loading mirror speeds from cached hostfile
 * base:
 * epel:
 * extras:
 * updates:
No package rar available.
Error: Nothing to do

I had previously installed support for the Extra Packages for Enterprise Linux (EPEL) repository, but though I thought the unrar package might be found there, it wasn't found. I did find an RPM file for the software, howerver, at RPM CentOS 7 unrar 5.0.12 x86_64 rpm. I downloaded that file with wget and, since yum can be used to install RPM files, installed it with yum.

[ More Info ]

[/os/unix/linux/centos/7] permanent link

Sat, Mar 25, 2017 10:56 pm

Using the more command to discard lines at the beginning of a file

If you wish to ignore lines at the start of output or in the beginning of a file, you can use the more command to do so. E.g., suppose I have a text file named fruit.txt that contains the following lines:


On a Linux, Unix, or OS X/macOS system, if I want to see all lines of the file but the first one, I can use the +n, where n is a number, argument to the more command. In this case, I can use more +2 fruit.txt to start the output at the second line in the file.

$ more +2 fruit.txt

If I wanted to ignore the first four lines and start output at the fifth line, I could use more +5.

$ more +5 fruit.txt

[ More Info ]

[/os/unix/commands] permanent link

Fri, Mar 24, 2017 10:31 pm

Redirecting SQLite output to a file

If you need to redirect the output of SQL commands to a file while using SQLite, you can do so using the .output command. E.g., I have an SQLite database on my MacBook Pro laptop running OS X that contains a table named Equipment. Within that table is a column named Device that is a description for the particular piece of equipment in the table entry. I can view just that field for all records with the SQLite command SELECT Device FROM Equipment. To direct the output of the command to a text file named device.txt, I can use the command .output device.txt. After executing the command to select the Device field from all records, I can then issue the .output command without any arguments to it to return to having the output of commands displayed on the console rather than going to the file.

$ sqlite3 ~/Documents/Work/CRQ/CRQ.db
SQLite version 2015-05-20 18:17:19
Enter ".help" for usage hints.
sqlite> .output device.txt
sqlite> SELECT Device FROM Equipment;
sqlite> .output

[/software/database/sqlite] permanent link

Fri, Mar 17, 2017 6:19 pm

OS X "arrange by" in column view

I usually have the OS X Finder set to display folders and files in alphabetical order by setting the view mode to arrange the display of files and folder by name. But sometimes I switch to view by size, etc. However, when I then switch back to view the files and folders in column mode arranged by name, Finder doesn't actually display them in alphabetical order, which is annoying.

I finally got to the point where the issue was so annoying that I felt I had to find a solution. I found Brett Taylor's HOWTO: Fix file sorting in Finder‘s column view on Mac OS X Lion article which provided a means to address the issue. Though the title for his article, which acknowledges Barney-15E's post at In OS X Lion, Finder will not "Arrange By > Name" in "Column view", references OS X Lion, I found the solution worked for OS X El Capitan (10.11.6) on my MacBook Pro.

[ More Info ]

[/os/os-x] permanent link

Thu, Mar 16, 2017 10:30 pm

Outlook 2016 unspecified encryption certificate message

After resolving a problem with my laptop not reading certificates stored on my Personal Identity (PIV) card. I've been able to decrypt email messages from others with Outlook 2016 on my MacBook Pro laptop running OS X El Capitan (10.11.6) by using my PIV card in the SCR331 card reader, but when I attempt to send an encrypted email, I see a message stating (image):

You have not specified an encryption certificate for this account. Once you send this encrypted message, you will not be able to read it. Do you still want to send this encrypted message?

If I click on Continue the email will be sent encrypted so that it is readable by the recipients when their email clients decrypt it using their private keys, but I am unable to read the message I sent when it is placed in my Sent folder. To resolve the problem, I clicked on Tools on the Outlook menu bar, then selected Accounts, then clicked on the Advanced button. I then clicked on the Security tab and selected a certificate in the Encryption section. It had been set to "None Selected".

[ More Info ]

[/security/encryption] permanent link

Tue, Mar 14, 2017 8:51 pm

Adding the SNMP service to a Windows 10 system

You can check on whether the Simple Network Management Protocol (SNMP) service has already been added to a Microsoft Windows 10 system by opening a Services window and scrolling through the list of services to see if SNMP is present. You can open a Services window to check the list of installed services by typing services in the Cortana "Ask me anything" field and hitting Enter. The best match shown should be "Services Desktop app". You can click on it to see the list of Windows services.

SNMP service not present

If you see SNMP Trap, but not SNMP Service, you will need to add the service. The process for adding it is similar to the process of adding support for SNMP under Windows 7.

[ More Info ]

[/os/windows/win10] permanent link

Sun, Mar 12, 2017 10:57 pm

Let's Encrypt certificate expired

A couple of days ago, a user showed me a message she saw on her system about a security certificate issue. When I looked at the message, I realized it was due to the expiration of the Let's Encrypt certificate on the email server used by her system. I logged into that system and queried the server with the openssl command to check the expiration date. I saw it had expired that day, March 10.

# echo "quit" | openssl s_client -connect -quiet
depth=2 O = Digital Signature Trust Co., CN = DST Root CA X3
verify return:1
depth=1 C = US, O = Let's Encrypt, CN = Let's Encrypt Authority X3
verify return:1
depth=0 CN =
verify error:num=10:certificate has expired
notAfter=Mar 10 19:53:00 2017 GMT
verify return:1
depth=0 CN =
notAfter=Mar 10 19:53:00 2017 GMT
verify return:1
+OK Dovecot ready.

From the root account, I renewed the certificate using the command letsencrypt renew.

[ More Info ]

[/security/encryption/openssl] permanent link

Sat, Mar 11, 2017 4:53 pm

Losing Internet connectivity via Wi-Fi on an OS X system

On my MacBook Pro laptop running OS X El Capitan (10.11.6), I've been losing Internet connectivity periodically. Though it appears I still have Wi-Fi connectivity, when I attempt to access websites through a browser I find that I can't access sites at times, though a moment before I had no issues browsing the Web. Firefox will display a "Server not found" message. If I go to a Terminal window and try to ping any IP address, I see "request timeout" messages.

$ ping
PING ( 56 data bytes
Request timeout for icmp_seq 0
Request timeout for icmp_seq 1
--- ping statistics ---
3 packets transmitted, 0 packets received, 100.0% packet loss

If I check the status of the WiFi connection using the airport command, I see that it is very noisy, though the signal stength is good, which I would expect, since the laptop is only a few feet from the wireless router.

$ /System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport -I
     agrCtlRSSI: -39
     agrExtRSSI: 0
    agrCtlNoise: -93
    agrExtNoise: 0
          state: running
        op mode: station 
     lastTxRate: 73
        maxRate: 72
lastAssocStatus: 0
    802.11 auth: open
      link auth: wpa2-psk
          BSSID: 94:44:52:4a:43:40
           SSID: Rain
            MCS: 7
        channel: 11

[ More Info ]

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

Wed, Mar 08, 2017 10:54 pm

Unable to read certificates from PIV card

I'd been having problems using a Personal Identity Verification (PIV) card with my MacBook Pro laptop running OS X El Capitan (10.10.5). I need the system to be able to access certificates on the PIV card in order to be able to decrypt email from some individuals. I have an SCR331 card reader, which attaches to the system via a Universal Serial Bus (USB) port.

SCR331 PIV card reader

If I attached the PIV card reader and clicked on the Apple icon at the top, left-hand corner of the screen and selected About This Mac then clicked on System Report, if I clicked on USB under Hardware, I would see the system recognized the card reader was attached. E.g., I saw "SCRx31 USB Smart Card Reader" for an SCR331 (that is a number on the underside of the device which appears to be its model number with a part number of 904875 listed there, also) PIV card reader I attached to the system via a USB port.

[ More Info ]

[/security/encryption] permanent link

Mon, Mar 06, 2017 11:28 pm

Finding files modified before or after a certain date with PowerShell

On a Microsoft Windows system, you can find files created before or after a specified date using the Get-ChildItem cmdlet. To use the cmdlet, open a PowerShell window - you can do so on a Windows 10 system by typing powershell in the Cortana "Ask me anything" window, hitting Enter, and then clicking on Windows PowerShell, which should be returned as the best match. If you wish to find files and directories before a certain date, you can use a command in the form Get-ChildItem | Where-Object {$_.LastWriteTime -lt date where date is the relevant date. E.g., on a system that uses the date format of mm/dd/yyyy where mm represents the month, dd the day and yyyy the year, a command like the one shown below, which returns a list of the files with a modification time prior to January 1, 2013, can be used:

PS C:\Users\Lila\documents> Get-ChildItem | Where-Object {$_.LastWriteTime -lt '1/1/2013'}

    Directory: C:\Users\Lila\documents

Mode                LastWriteTime         Length Name
----                -------------         ------ ----
d-----         9/9/2012  10:36 PM                Book Collector
d-----        11/8/2012   8:25 AM                Corel PaintShop Pro
d-----         4/6/2012   2:37 PM                recovered
-a----        4/14/2012   4:16 PM      761476464 Disc1.bin
-a----        4/14/2012   4:16 PM            941 Disc1.cue

PS C:\Users\Lila\documents>

[ More Info ]

[/os/windows/PowerShell] permanent link

Sat, Mar 04, 2017 10:00 pm

CSS max-width and min-width for @media

The third specification of the Cascading Style Sheets (CSS) style sheet language, CSS 3 provides support for media queries, which can adjust the display of information in a browser based on screen resolution, e.g. smartphone screen vs. computer screen, the width of the browser viewport, etc. This is done through the use of "@media, which can be used in a style sheet or a style element included in the <head> section of the HTML code.

Two parameters that can be used with @media are shown below:

max-widthThe maximum width of the display area, such as a browser window
min-widthThe minimum width of the display area, such as a browser window

[ More Info ]

[/network/web/html/css] permanent link

Fri, Mar 03, 2017 10:50 pm

Data loss provided by Microsoft's security "feature"

I was reminded tonight why one should avoid using Microsoft's latest desktop operating system, Windows 10, for any critical system. I had postponed some work on a Microsoft Windows 10 system that I was connected to by a Remote Desktop Protocol (RDP) connection. I had been working on the system a few days ago and returned to using the connection this evening only to see the system was going to reboot in a few minutes for an automatic update. I often have many applications and windows open at once and I knew there wasn't enough time for me to save all of my work, but I thought, even though I only had a few minutes remaining until the forced reboot, that I could at least postpone the reboot until tomorrow evening using the steps at Changing the time for a Windows 10 automatic restart that I've used before to postpone the forced reboot due to a software update. However, tonight when I got to the Windows Update settings window where a "Restart now" button appears, I was not able to click on "Change active hours" because that option did not appear under the "Restart now" button. I frantically tried to find another alternative. I thought, perhaps, I could hibernate the system to save the work in progress, but it was too late; the system rebooted and I lost all of the work in progress, much of which I'll be unable to recreate, since it had been several days since I had been working on the system and I now can't rememeber what I had put in some open Notepad windows, etc.

I understand the need to update systems to install security patches to prevent malware attacks, etc., but I've never lost data on this system over the course of several years due to such issues. I've only lost data due to Microsoft's automatic reboot "security feature".

I've read Microsoft is deigning to give their users a little more control over reboots due to automatic updates with the release of the Windows 10 "Creator's Edition" in April of 2017, e.g., see Windows 10 now prevents random reboots during updates, but Microsoft's decision that rebooting a system while a user is working on it even when there are open unsaved files, because Microsoft has decided that "this is for your own protection and too bad if you lose data" gives me a much more negative view of the company and its products. And I know there are many others similarly angered at the company after losing work to these forced reboots in Windows 10.

[/os/windows/win10] permanent link

Thu, Mar 02, 2017 9:52 pm

Extracting embedded documents from an Excel .xlsm file

I often receive Microsoft Excel files that have documents created by other Microsoft applications embedded within them. E.g., at the top of a worksheet I may see something like =EMBED("Visio.Drawing.11","").

EMBED Visio.Drawing

Sometimes I want to extract the embedded file. With a Microsoft Excel .xlsm file that is easy to do, because XLSM is a zipped, XML-based file format. To extract embedded documents, such as Visio drawings or PowerPoint presentations, I make a copy of the .xlsm file then rename the copy's extension from .xlsm to .zip. I can then extract the contents of the zip file. Within the directory that holds the extracted files, there will be a xl directory. Within that directory there is a media directory and within the media directory there is an embeddings directory that holds the embedded files, such as the Visio drawings in the example below.

$ ls ~/Documents/Work/CRQ/843940/unzipped
[Content_Types].xml	customXml		xl
_rels			docProps
$ ls ~/Documents/Work/CRQ/843940/test/xl
_rels			comments19.xml		comments9.xml
calcChain.xml		comments2.xml		ctrlProps
charts			comments20.xml		drawings
comments1.xml		comments21.xml		embeddings
comments10.xml		comments22.xml		media
comments11.xml		comments23.xml		printerSettings
comments12.xml		comments24.xml		sharedStrings.xml
comments13.xml		comments3.xml		styles.xml
comments14.xml		comments4.xml		theme
comments15.xml		comments5.xml		vbaProject.bin
comments16.xml		comments6.xml		workbook.xml
comments17.xml		comments7.xml		worksheets
comments18.xml		comments8.xml
$ ls ~/Documents/Work/CRQ/843940/unzipped/xl/media
image1.png	image2.jpeg	image4.emf	image6.emf	image8.emf
image10.emf	image3.emf	image5.emf	image7.emf	image9.png
$ ls ~/Documents/Work/CRQ/843940/unzipped/xl/embeddings

[ More Info ]

[/software/office/excel] permanent link

Wed, Mar 01, 2017 10:42 pm

Discarding configuration changes for a Juniper SRX router/firewall

If you've been entering commands for configuration changes on a Juniper Neworks SRX router/firewall, which runs the Juniper Network Operating System, Junos OS, but haven't committed those changes to make them active, you can discard them using the command rollback 0. which will replace the "candidate config", i.,e., the one you've been editing, with the active configuration, which is also the boot configuration.
root@Alder# rollback 0
load complete


The device can store multiple prior configurations and you can revert to one of those other prior configurations, instead, using rollback n where n is the number for the prior configuration. You can also rollback to a saved "rescue" configuration with rollback rescue. You an see a list of the stored configurations to which you can revert using the command rollback ?.

[ More Info ]

[/security/firewalls/SRX] permanent link

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