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Serial terminal connection to a Raspberry Pi over gpio pins

I have a Pi 3 that’s been running PiAware for a number of years, and been updated/upgraded over the years. It’s been running reliably and stays up and accessible for months with no issues, but only recently, somewhat randomly, it started becoming unreachable on my local wifi.

Since it’s running headless, I don’t normally have a screen or keyboard attached to it, and if I need to access it then I ssh into it over wifi. Without ssh access I was kind of in the dark what was going on. The power and activity lights were still on/flickering, so I knew it hadn’t crashed completely.

I remembered I had a USB/Serial cable in my box of cables somewhere, but had actually not used it since Pi 1 days, so looked around for the correct steps to connect it.

For a diagram of what colour connectors to connect to what GPIO pins, see: https://www.jeffgeerling.com/blog/2021/attaching-raspberry-pis-serial-console-uart-debugging

List serial connections over USB:

ls /dev | grep usb

For me this shows:

❯ ls /dev | grep usb
cu.usbserial-11240
tty.usbserial-11240

To connect with screen:

screen /dev/tty.usbserial-11240 115200

To exit, type Ctrl-A then Ctrl-D (from here)

To connect with minicom:

minicom -b 115200 -D /dev/tty.usbserial-11240

Esc then X to exit.

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ssh to solaris 10 error: “no matching key exchange method found”

I first ran into this error after installing Solaris 10 on a Sun Ultra 60 that I had a while back, but I’ve recently ran into it again installing Solaris 10 on Proxmox:

Unable to negotiate with 192.168.1.95 port 22: no matching key exchange method found. Their offer: gss-group1-sha1-toWM5Slw5Ew8Mqkay+al2g==,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1

The solution to configure my Mac to be able to use older key algorithms was a combination from here and answers on this post.

I edited my ~/.ssh/config and added a Host entry for the ip of my Solaris 10 instance, adding:

Host 192.168.1.95
    HostKeyAlgorithms=+ssh-dss,ssh-dss
    KexAlgorithms +diffie-hellman-group1-sha1

And now I can just ssh in as normal (no need for any additional params as shown in the first post, as the required options are configured in my .ssh/config.

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Creating new Oracle user, new instance

Running Oracle 19c in Docker, I connected with sqlplus and attempted to create a new user:

create user example identified by password;

and got this cryptic error:

ORA-65096: invalid common user or role name

Per answers on this post, this is usually because you connected to the root container database (CDB) instead of a pluggable container database (PDB).

You can cofirm what you are connected to with:

show con_name

and sure enough, I’m connected to CDB$ROOT:

CON_NAME 
------------------------------
CDB$ROOT

List available PDBs with:

show pdbs

shows:

    CON_ID CON_NAME                       OPEN MODE  RESTRICTED
---------- ------------------------------ ---------- ----------
         2 PDB$SEED                       READ ONLY  NO        
         3 ORCLPDB1                       READ WRITE NO

Updating my connection properties to connect to SERVICE=ORCLPDB1 and now I’m good.

To grant all privs to a new user:

grant all privileges to username

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