[Google Cloud][Compute Engine] Linux basics commands not found on startu-scripts - bash

Question

I'm having trouble running a VM's startup scripts for instance groups. Commands like touch, cat, chmod are not found.
ubuntu#instance-template-****-1:~$ sudo google_metadata_script_runner -d --script-type startup
startup-script: INFO Starting startup scripts.
startup-script: INFO Found startup-script-url in metadata.
startup-script: INFO Downloading url from https://storage.googleapis.com/bucket-*****/startup-image to /home/ubuntu/startup-scripts/script using authentication token.
startup-script: INFO startup-script-url: /home/ubuntu
startup-script: INFO startup-script-url: /home/ubuntu
startup-script: INFO startup-script-url: /home/ubuntu/startup-scripts/script: line 11: touch: command not found
startup-script: INFO startup-script-url: /home/ubuntu/startup-scripts/script: line 12: touch: command not found
startup-script: INFO startup-script-url: /home/ubuntu/startup-scripts/script: line 13: touch: command not found
startup-script: INFO startup-script-url: /home/ubuntu/startup-scripts/script: line 15: chmod: command not found
startup-script: INFO startup-script-url: /home/ubuntu/startup-scripts/script: line 16: chmod: command not found
startup-script: INFO startup-script-url: /home/ubuntu/startup-scripts/script: line 71: ssh-keyscan: command not found
startup-script: INFO startup-script-url: /home/ubuntu/startup-scripts/script: line 72: ssh-keygen: command not found
startup-script: INFO startup-script-url: /home/ubuntu/startup-scripts/script: line 74: cat: command not found
startup-script: INFO startup-script-url: /home/ubuntu/startup-scripts/script: line 76: git: command not found
startup-script: INFO startup-script-url: /home/ubuntu/startup-scripts/script: line 78: sh: command not found
startup-script: INFO startup-script-url: Return code 127.
startup-script: INFO Finished running startup scripts.
Script:
#!/bin/bash
PATH=/home/ubuntu
cd $PATH
touch $PATH/.ssh/id_rsa
touch $PATH/.ssh/id_rsa.pub
touch $PATH/.ssh/known_hosts
chmod 644 $PATH/.ssh/id_rsa.pub
chmod 600 $PATH/.ssh/id_rsa
echo $IDRSA > $PATH/.ssh/id_rsa
echo $IDRSA_PUB > $PATH/.ssh/id_rsa.pub
ssh-keyscan bitbucket.org >> bitbucketKey
ssh-keygen -lf bitbucketKey
cat bitbucketKey >> $PATH/.ssh/known_hosts
git clone git#bitbucket.org:repo/repo.git
sh ./repo/prepare
PROJECT_ID=$(curl "http://metadata.google.internal/computeMetadata/v1/project/numeric-project-id" -H "Metadata-Flavor: Google")
./repo/deploy/run --dev --project-id=$PROJECT_ID

Answer 1

When you set PATH=/home/ubuntu, it overwrites the value of PATH environment variable that you're supposed to get in the shell and it forces the subsequent commands to end up in "command not found" error, because the appropriate executable files for running those commands are not available on new path /home/ubuntu that you just set. You can workaround this by renaming that variable to any name other than PATH and all of its occurrences in your script. You can use the same variable name in lower case too. (like path=home/ubuntu).
The PATH environment variable is a colon-delimited list of directories that your shell searches through when you enter a command. Program files (executables) are kept in many different places on the Unix system. Your path tells the Unix shell where to look on the system when you request a particular program.

Answer 2

You modified the PATH environment in your script:
PATH=/home/ubuntu
However, PATH is a Shell Variables of bash:
PATH The search path for commands. It is a colon-separated list of directories in which the shell looks for commands (see
COMMAND EXECUTION below). A zero-length (null) directory name in the value of PATH indicates the current directory.
A null directory name may appear as two adjacent colons, or as an initial or trailing colon. The default path is
system-dependent, and is set by the administrator who installs bash. A common value is ``/usr/local/bin:
/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin''.
Therefore almost all commands cannot be found. (Unless they are under /home/ubuntu)
If you just want to set a variable as a user folder to operate with the script, please change the variable name to like MY_HOME.
#!/bin/bash
MY_HOME=/home/ubuntu
cd $MY_HOME
touch $MY_HOME/.ssh/id_rsa
touch $MY_HOME/.ssh/id_rsa.pub
touch $MY_HOME/.ssh/known_hosts
...