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====== ALICE beast machine admin info ======

This page contains information on how to manage the ALICE beast machine.

For a description of the machine hardware and WIP [[alicecrunchwip | click here]]

===== Brief storage view ======

<code>
 system SSD (M.2) 90GB
    /       # system root
    /opt    # folder for user software
    /var    # folder for logs and other runtime things
    /tmp    # temporary folder
 emergency admin user homes SSD (M.2) 90GB
    /ahome  
  >>>> There is still time to change these. Please speak up. I could for example allocate more space for system and opt instead of the one allocated for /ahome. <<<<

 user homes SSD (U.2) 690GB
    /home   # user home folders
    
 data disk (RAID6) 55TB
    /disk   # available for data, filesize >= 1MB 
</code>

===== Admin rights ======

Direct access to root user is discouraged. Administrators should use the ''sudo'' command to become root.

There is a special user whose home folder is located in ''/ahome'' in case the home folders get corrupted, called ''alicedrift''. You are free to create a password for such user and share it among the group. I recommend you do this asap. This is to be used in case of emergency.

==== Adding an administrator ====

To elect a new administrator, it is enough to add them to the ''wheel'' unix group. 

:!: Fiddling with sudo configuration files is strongly discouraged. :!:

<code:bash>
usermod -aG wheel <username>
</code>
Example:
<code:bash>
usermod -aG wheel pflorido
</code>

===== Software planning =====

I suggest you install system software according to the distribution, using ''yum''.

As for research software, I would recommend you install:
  * For small files that require performance:
    * in the ''/opt'' folder (SSD) 
    * in a subfolder of ''/home'' (SSD U.2)
  * For large/huge files (> 1MB ) such as docker images, create a specific folder inside the ''/disk'' folder (RAID)

===== Software installation =====

For system/distribution software installation it is recommended to use the ''yum'' command and the ''rpm'' system. Centos7 is a RedHat based distribution. The commands are pretty much the same as ubuntu. Here I give you a quick reference of most useful commands.

==== Search for a package ====

<code:bash>
yum search <string>
</code>
Example:
<code:bash>
yum search tmux
</code>

==== Install a package ====

<code:bash>
yum install <packagename>
</code>
Examples:
<code:bash>
yum install tmux
</code>

==== Find which package contains a specific file ====

<code:bash>
yum provides */<expression>
</code>
Examples:
<code:bash>
yum provides */libboost*
</code>

==== upgrade system packages ====

<code:bash>
yum upgrade
</code>

You will be asked to accept the changes.

===== Emergency procedures =====

:WIP:

This section describes how to handle some critical situations.

In what follows I will use terminology that I clarify below.

  * **RAID**: a device managed by a physical RAID controller card.
  * **swRAID**: a device managed by software RAID, which is a feature of the kernel to create RAID disks. Such feature is less reliable than an actual physical raid but it should give enough time to take action when something breaks. It includes you being able to finish a running job before shutting down the machine. 

==== RAID disk failing ====

This can happen if one or more of the RAID disks are broken or starting to fail. You are supposed to take action asap.

> How to detect?

> What to do

==== Home folder swRAID failing ====

There are two U.2 disks in software RAID serving user homes. Should one disk fail, the homes will continue to work, but as soon as possible you are required to replace the broken disk to avoid data loss.

This can happen if one of the U.2 disks containing home folders is faulty.

> How to detect?

> What to do

==== system swRAID failing ====

The system M.2 disk is in software raid with two partitions of the U.2 disk. This allows the machine to continue working when the M.2 disk is faulty. However, the machine will not reboot in case this disk breaks. Unfortunately the U.2 disks cannot be used for booting. It is a limitation of the machine. 

Nevertheless it's possible to entirely restore the disk image by copying one of the two copies in the U.2 drives. See description below.

> How to detect?

> What to do
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