DataDomain Bash Shell (or: So You Want to Wreck Your DataDomain)

When dealing with the care and feeding of DataDomain arrays, there are occasions where it helps to know how to access the array's "Engineering Mode". In actuality, there are two levels of engineering mode for DataDomains:

• SE Shell: the SE (system engineer) shell mode is a superset of the normal system administration shell. It includes all of the management commands of the normal administration shell plus some powerful utilities for doing lower-level maintenance tasks on your DataDomain. These include things like fixing ACLs on your CIFS shares, changing networking settings (e.g., timeouts related to OST sessions) and other knobs that are nice to be able to twizzle
• BASH Shells: While the SE shell mode gives you more utilities for managing the array, they're still wrapped in the overall DDOS command-shell construct. The BASH shell mode is pretty much just like a normal root shell on a Linux system: you're able to script tasks in it, use tools like `find`, etc. Take all the damage you can do in the SE mode and add on the capability of doing those tasks on a massive, automated scale.

While enabling SE mode can likened to enabling you to shoot your foot off with a .22, the BASH mode could be likened to enabling you to shoot your foot off with a howitzer. Where SE mode is merely dangerous, I can't really begin to characterize the level of risk you expose yourself to when you start taking full advantage of the DataDomain's BASH shell.

Since accessing either of these modes isn't well-documented (though there's a decent number of Google searches that will turn up the basic "SE" mode) and I use this site as a personal-reminder on how to do things. I'm going to put the procedures here.

Please note: use of engineering mode allows you to do major amounts of damage to your data with a frightening degree of ease and rapidity. Don't try to access engineering mode unless you're fully prepared to have to re-install your DataDomain - inclusive of destroying what's left of the data on it.

Accessing SE Mode:

1. SSH to the DataDomain.
2. Login with an account that has system administrator privileges (this may be one of the default accounts your array was installed with, a local account you've set up for the purpose or an Active Directory managed account that has been placed into a Active Directory security-group that has been granted the system administrator role on the DataDomain
3. Get the array's serial number. The easiest way to do this is type `system show serialno` at the default command prompt
4. Access SE mode by typing `priv set se`. You will be prompted for a password - the password is the serial number from the prior step.

At this point, your command prompt will change to "SE@<ARRAYNAME>" where "<ARRAYNAME>" will be the nodename of your DataDomain. While in this mode, an additional command-set will be enabled. These commands are accessed by typing "se". You can get a further listing of the "se" sub-commands in much the same way you can get help at the normal system administration shell (in this particular case: by typing "se ?").


Accessing the SE BASH Shell:
Once you're in SE mode, the following command-sequence will allow you to access the engineering mode's BASH shell:

1. Type "fi st"
2. Type "df"
3. Type <CTRL>-C three times
4. Type "shell-escape"

At this point, a warning banner will come up to remind you of the jeopardy you've put your configuration in. The prompt will also change to include a warning. This is DataDomain's way of reminding you, at every step, the danger of the access-level you've entered.

Once you've gotten the engineering BASH shell, you have pretty much unfettered access to the guts of the DataDomain. The BASH shell is pretty much the same as you'd encounter on a stock Linux system. Most of the GNU utilities you're used to using will be there and will work the same way they do on Linux. You won't have man pages, so, if you forget flags to a given shell command, look them up on a Linux host that has the man pages installed.

In addition to the standard Linux commands will be some DataDomain-specific commands. These are the commands that are accessible from the "se" command and its subcommands. The primary use-case for exercising these commands in BASH mode is that the BASH mode is pretty much as fully-scriptable as a root prompt on a normal Linux host. In other words, take all the danger and power of SE mode and wrap it in the sweaty-dynamite of an automated script (you can do a lot of modifications/damage by horsing the se sub-commands to a BASH `find` command or script).