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How to find files modified more than X days ago

search

Find files modified more than 48 hours ago:

$ find /path -mtime +1

Find files modified more than n=90 days ago (cutoff by the hour, not the day).

$ find /path -mtime +89

Note the +(n-1) in command. Many online articles got this wrong by simply putting +90.

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How to prevent accidental keyboard input in a Linux terminal

 
In a multi-monitor setup, sometimes I type in the wrong window without knowing and end up spamming WeeChat IRC.

To prevent that, I now use gnome-terminal and turn on “Read-Only” mode to disable typing. This useful feature is, however, not available in other terminals. Please share in the comments if you know of alternatives.

2018 Mar 27 UPDATE: xfce4-terminal also has a “Read-Only” mode.
2018 May 7 UPDATE: konsole too.

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How to change sshd default port on firewalld

 
Instead of messing around with the ports directly with RHEL7/CentOS7 firewall-cmd, I’ve decided to update the port number in the ssh.xml service file instead. Think it’s cleaner this way.

For example, here are the steps to change sshd port from the default 22 to 9876:

1. Make a copy of the default ssh service file:
cp /usr/lib/firewalld/services/ssh.xml /etc/firewalld/services/

2. Inspect current firewall settings
iptables -nL | grep -e 22 -e 9876
ACCEPT     tcp  —  0.0.0.0/0            0.0.0.0/0            tcp dpt:22 ctstate NEW

3. Edit /etc/firewalld/services/ssh.xml to change port number
From: <port protocol=”tcp” port=”22″/>
To: <port protocol=”tcp” port=”9876″/>

4. Change /etc/ssh/sshd_config port to 9876

5. Restart sshd
systemctl restart sshd

6. Notice that sshd now listens on new port
netstat -punta

7. Reload firewalld, which will pick up the new port in ssh.xml
firewall-cmd –reload

8. Inspect new firewall settings, notice port changed
iptables -nL | grep -e 22 -e 9876
ACCEPT     tcp  —  0.0.0.0/0            0.0.0.0/0            tcp dpt:9876 ctstate NEW

9. Test

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How to reset lost root password on Raspberry Pi running Arch Linux

 
Assumption: SD is not encrypted

Plug SD onto another working computer, look for the “cmdline.txt” file and edit it by appending “init=/bin/sh” after “rootwait”. Save the file, remove the SD and plug it back to the RPi and boot.

You’ll be dropped into a shell. Change your passwd, then hit CTRL-ALT-DEL to trigger a reboot. Switch off the RPi when the shutdown completes, just before the boot starts. Unplug the SD and plug it onto the other working computer. Remove “init=/bin/sh” from “cmdline.txt” file.

Plug the SD back onto the RPi, boot and you can now login with the newly reset password.

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How to fix network print queue installation error 0x0000007e on Windows

Printer-Error

Problem:

The print queue of a HP printer on a Windows 2003 Server (clustered) already has its 32-bit driver installed.

For my new 64-bit Windows 7 client to use the print queue, I installed the 64-bit printer driver on the server.

However, when I connect to the print queue on the 64-bit Windows 7 client, at the end of the installation, it will fail with error:

Windows cannot connect to the printer
Operation failed with error 0x0000007e

Solution:

Delete the “CopyFiles” key from HKLM\Cluster\Resources\<LongString>\Parameters\Printers\<QueueName>

Non-clustered server may have the key at HKLM\SYSTEM\CurrentControlSet\Control\Print\Printers\<QueueName>. Just do a search in regedit using your QueueName to find the right location.

Remember to backup the key before changing the registry.