1. In the terminal window enter the command sudo hostnamectl set-hostname newname where newname is the new name you wish to assign to the system. E.g.:

   jim@Firefly:~$ sudo hostnamectl set-hostname Smaug
   [sudo: authenticate] Password: 
   jim@Firefly:~$

   That will change the host name stored in /etc/hostname.

2. Then edit the /etc/hosts file, replacing the old host name there with the new one. E.g., if I had the following lines in the hosts file, I would modify the second line containing the old host name.

   127.0.0.1 localhost
   127.0.1.1 Firefly
   

   The 127.0.0.1 in the above lines is the localhost IP address, a loopback address that can be used when troubleshooting network issues. Ubuntu also adds a 127.0.1.1 address in /etc/hosts with the name you have assigned to the system. The name should match the one in /etc/hostname, so change the name for the 127.0.1.1 address to the new name you wish to use.

References:

1. What is difference between localhost address 127.0.0.1 and 127.0.1.1
   Updated: April 2, 2021
   Ask Ubuntu

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

If you need to change the password, i.e., the encryption key, used to encrypt a partition with Linux Unified Key Setup (LUKS) on a Linux system, you can open a terminal window and use the command sudo cryptsetup luksChangeKey /dev/sdaX where sdaX is the relevant partition. E.g., I needed to change the password on a Ubuntu Linux system where the user's data was stored on /dev/sda3.

jim@Firefly:~$ sudo cryptsetup luksChangeKey /dev/sda3
Enter passphrase to be changed:
Enter new passphrase:
Verify passphrase:
jim@Firefly:~$

If you don't know the designation for the encrypted partition, e.g., if I didn't know it was sda3, I could use the lsblk command (it is part of the util-linux package) to determine it. E.g.:

jim@Firefly:~$ lsblk
NAME                      MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINTS
loop0                       7:0    0     4K  1 loop  /snap/bare/5
loop1                       7:1    0  73.9M  1 loop  /snap/core22/2133
loop2                       7:2    0  11.8M  1 loop  /snap/desktop-security-center/59
loop3                       7:3    0 247.6M  1 loop  /snap/firefox/6966
loop4                       7:4    0  11.1M  1 loop  /snap/firmware-updater/167
loop5                       7:5    0  91.7M  1 loop  /snap/gtk-common-themes/1535
loop6                       7:6    0  14.4M  1 loop  /snap/prompting-client/104
loop7                       7:7    0 516.2M  1 loop  /snap/gnome-42-2204/226
loop8                       7:8    0  17.5M  1 loop  /snap/snap-store/1300
loop9                       7:9    0  50.8M  1 loop  /snap/snapd/25202
loop10                      7:10   0   576K  1 loop  /snap/snapd-desktop-integration/315
loop11                      7:11   0 226.2M  1 loop  /snap/thunderbird/812
sda                         8:0    0 953.9G  0 disk
├─sda1                      8:1    0     1G  0 part  /boot/efi
├─sda2                      8:2    0     2G  0 part  /boot
└─sda3                      8:3    0 950.8G  0 part
  └─dm_crypt-0            252:0    0 950.8G  0 crypt
    └─ubuntu--vg-ubuntu--lv
                          252:1    0 950.8G  0 lvm   /
jim@Firefly:~$

From the above output, I can see that the disk drive in the system is designated as sda and the encrypted partition is sda3 (it is listed as type "crypt").

[ More Info ]

[/security/encryption/LUKS] permanent link

[/network/ssh/putty] permanent link

To view the list of user-defined applications on a Juniper Networks router/firewall running the JunOS operating system from a command-line interface (CLI), you can enter cli mode by issuing the command cli after logging in and then issue the command show configuration applications.

root@Bellatrix> show configuration applications
application POP3 {
    protocol tcp;
    destination-port 110;
}
application POP3S {
    protocol tcp;
    destination-port 995;
}
application Rising_World_TCP {
    protocol tcp;
    destination-port 4254-4259;
}
application Rising_World_UDP {
    protocol udp;
    destination-port 4254-4259;
}

root@Bellatrix>

To view the list of predefined junos- applications from the CLI, you can enter cli mode by issuing the command cli after logging in and then issue the command show configuration groups junos-defaults applications.

[ More Info ]

[/security/firewalls/SRX] permanent link

To determine what process is listening on a particular TCP port on a Linux system, you can use the ss command. On a CentOS Linux system, the command can be found in the /sbin/ss directory. The utility is part of the iproute, or iproute2 package.

# which ss
/sbin/ss
# rpm -qf /sbin/ss
iproute-3.10.0-21.el7.x86_64
#

To see help information on the utility, you can use the command ss --help.

# ss --help
Usage: ss [ OPTIONS ]
       ss [ OPTIONS ] [ FILTER ]
   -h, --help           this message
   -V, --version        output version information
   -n, --numeric        don't resolve service names
   -r, --resolve       resolve host names
   -a, --all            display all sockets
   -l, --listening      display listening sockets
   -o, --options       show timer information
   -e, --extended      show detailed socket information
   -m, --memory        show socket memory usage
   -p, --processes      show process using socket
   -i, --info           show internal TCP information
   -s, --summary        show socket usage summary
   -b, --bpf           show bpf filter socket information

   -4, --ipv4          display only IP version 4 sockets
   -6, --ipv6          display only IP version 6 sockets
   -0, --packet display PACKET sockets
   -t, --tcp            display only TCP sockets
   -u, --udp            display only UDP sockets
   -d, --dccp           display only DCCP sockets
   -w, --raw            display only RAW sockets
   -x, --unix           display only Unix domain sockets
   -f, --family=FAMILY display sockets of type FAMILY

   -A, --query=QUERY, --socket=QUERY
       QUERY := {all|inet|tcp|udp|raw|unix|packet|netlink}[,QUERY]

   -D, --diag=FILE     Dump raw information about TCP sockets to FILE
   -F, --filter=FILE   read filter information from FILE
       FILTER := [ state TCP-STATE ] [ EXPRESSION ]
#

Or you can consult the manual page for ss using the command man ss.

[ More Info ]

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

An .htpasswd file can be used to control access to specific directories that visitors to a web server can access when the web server is an Apache web server. Entries in the file can be added, modified, or deleted using the htpasswd utility, which may be in the /bin directory on a Linux sysem. To update a password for a user listed in an .htpasswd file, a command in the form htpasswd htpasswdFileLocation user where htpasswdFileLocation is the location and name for the .htpassword file on the system and user is a specific user listed in that file. The htpasswd utility will prompt for a new password and then prompt you to retype it to ensure there has not been a typo when the new password was provided. E.g.:

# htpasswd /home/jdoe/music/.htpasswd mary
New password:
Re-type new password:
Updating password for user mary
#

If you wish to delete an entry for a user in the .htpasswd file, you can use a command in the form htpasswd -D htpasswdFileLocation user. The -D indicates the entry for the user should be deleted. The response will indicate the password for the user was deleted, which is true, but that indicates the entire entry for that user was removd from the file. E.g.:

# htpasswd -D /home/jdoe/music/.htpasswd manny
Deleting password for user manny
#

Related

1. Apache AllowOverride AuthConfig Directive
   Date: May 13, 2008

[/network/web/server/apache] permanent link

Microsoft provides Secure Shell (SSH) server software with Windows 11 that you can use to listen for connections from remote SSH clients, but the server service is not installed by default. To install the Microsoft-provided SSH server software on a Windows 11 system, take the following steps:

1. Type optional features in the Windows Search field at the bottom of the screen and hit Enter, then click on "Open" when it is found.
2. Click on the View features button.
3. Scroll down the list of optional features until you see Open SSH Server and then click on the check box for it and click on the Next button.
4. Click on the Add button to add the OpenSSH Server capability to the system.
5. When the Optional features window shows that the OpenSSH Server software has been added, you can close the window. If you scroll down the list of added features before closing the window, you should see OpenSSH Server below OpenSSH Client.

After installing the software, you will need to start the OpenSSH server service.

[ More Info ]

[/os/windows/network/ssh/OpenSSH] permanent link

If you wish to delete all of the records from a table in an SQLite database, you can do so using a command in the form delete from tableName where tableName is the name of the table from which you wish to remove all of the rows in the table. E.g., if I wished to delete all of the records in a table named TimeStamps, I could use the delete command below.

sqlite> select * from Timestamps;
2025-05-01 21:26:22|2025-05-01 21:23|10947739
2025-05-01 21:28:33|2025-05-01 21:28|10967247
2025-05-04 13:37:47|2025-05-04 13:36|18079581
sqlite> delete from Timestamps;
sqlite> select * from Timestamps;
sqlite>

If I only wanted to delete a record or records meeting a specific condition, I could specify that condition in a WHERE clause. E.g., if the columns in the table were CurrentTimestamp, LastUpdateTimestamp, and Size and I only wanted to remove the row where the value of CurrentTimestamp is 2025-05-04 13:37:47, I could use the command below, instead.

sqlite> .schema Timestamps
CREATE TABLE "Timestamps" (
        "CurrentTimestamp"      TEXT NOT NULL,
        "LastUpdateTimestamp"   TEXT NOT NULL,
        "Size"  INTEGER NOT NULL
);
sqlite> delete from Timestamps where CurrentTimestamp='2025-05-04 13:37:47';

[/software/database/sqlite] permanent link

[ More Info ]

[/security/antivirus/avira] permanent link

I booted a PC from a USB flash drive on which I had installed Lubuntu Linux. I also plugged another flash drive into the system, but I didn't know where it was mounted. The hard disk drive (HDD) in the system was /dev/sda and I assumed the Lubuntu Linux bootable drive was /dev/sdb and the new drive would be /dev/sdbc. You can type for devlink in /dev/disk/by-id/usb*; do readlink -f ${devlink}; done at a shell prompt, which you can obtain on a Lubuntu system by clicking on the bird icon at the lower, left-hand corner of the screen and selecting System Tools then Qterminal, to see a list of the USB devices attached to a system.

lubuntu@lubuntu:~$ for devlink in /dev/disk/by-id/usb*; do readlink -f ${devlink}; done
/dev/sdc
/dev/sdc1
/dev/sdb
/dev/sdb1
lubuntu@lubuntu:~$

You can find the location where a USB drive is mounted by issuing the mount command and then piping the output into the grep command to find information on just the particular drive in which you are interested.

lubuntu@lubuntu:~$ mount | grep sdc
/dev/sdc1 on /media/lubuntu/EMTEC C450 type vfat (rw,nosuid,nodev,rela
time,uid=1000,gid=1000,fmask=0022,dmask=0022,codepage=437,iocharset=is
o8859-1,shortname=mixed,showexec,utf8,flush,errors=remount-ro,uhelper=udisks2)
lubuntu@lubuntu:~$

In this case, I knew the USB flash drive was a 16GB Emtec device and I was able to see it was mounted at /media/lubuntu/EMTEC C450. I was then able to view the files and folders for the drive from the shell prompt.

lubuntu@lubuntu:~$ ls /media
cdrom  lubuntu  root
lubuntu@lubuntu:~$ ls /media/lubuntu
'EMTEC C450'
lubuntu@lubuntu:~$ ls /media/lubuntu/'EMTEC C450'
 EMTEC.icns   EMTEC.ico  'System Volume Information'   autorun.inf
lubuntu@lubuntu:~$

References:

1. How do I figure out which /dev is a USB flash drive?
   Date: September 16, 2008
   superuser

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