Replacing a Failed Drive

Fixing a Broken System

Power outages in particular, and other types of system failure, can result in a broken system which cannot be booted, while the hardware is still good.

Using an Install Boot Disk

If an installation DVD of the same version as a system is available, then the disk may be used to attampt a system repair.

Adding a Replacement Drive

A replacement SSD drive may be added connected to a USB 3.0, USB 3.1/C, or Thunderbolt port. A completely fresh OS install would be performed on the new drive, and the Refind boot manager would be added to allow boot selection. See Configuring a Mac Mini Server and Installation Instructions for details on these steps.

Recovering Partition Data

Once an OS is fully installed on a replacement drive, system recovery proceeds as follows:

  • Configure rEFInd to boot from the replacement system drive, then boot from the new system (see Download and Install rEFInd)

  • Mount the corrupted system partition. For example, to mount sdb3:

    sudo mkdir /mnt/sdb3
sudo mount -t ext4 /dev/sdb3 /mnt/sdb3

  • Enumerate user folders and shares on the corrupted partition:

    ls -al /mnt/sdb3/home/samba/profiles
ls -al /mnt/sdb3/home/samba/shares

  • Zentyal:

    • Configure file sharing, users, and other services in the new OS
    • Enter users to the new OS for SAMBA profiles on the corrupted partition
    • Setup file shares in the new OS for SAMBA shares on the corrupted drive

  • Remove ACLs (Access Control Lists) from profiles on corrupted partition:

    setfacl -bnR /mnt/sdb3/home/samba/profiles/*

  • Copy all user data from profiles to corresponding users in new system:

    cp -r /mnt/sdb3/home/samba/profiles/{user1}/* /home/samba/profiles/{user1}/
...

  • Remove ACLs (Access Control Lists) from shares on corrupted partition:

    setfacl -bnR /mnt/sdb3/home/samba/shares/*

  • Copy all SAMBA shares from corrupted partition to new system:

    cp -r /mnt/sdb3/home/samba/shares/{share1}/* /home/samba/shares/{share1}
...

  • Unmount the corrupted partition:

    umount /mnt/sdb3

  • Reboot system and test access to all shares.

Commands for Recovery

Identifying a Partition

Boot from a new OS, probably on an SSD drive. Open a terminal window, then verify the drive volume to mount. The following commands may help identify the device to mount:

df -h | grep "/sd"
mount | grep "/sd"
ls -al /dev/sd*

Reading and setting Mode

The long-form file directory listing displays file mode permissions:

ls -al {directory}

A plus sign (+) displays to the right of the mode when ACLs apply to an entry.

The chmod changes the permissions mode for a file or directory:

chmod -Rf 744 ~/Downloads

The chown changes the owner and group for a file or directory:

chown admin:__users__ /home/samba/shares/shared

Reading ACLs

To read or display ACLs on a file, use command:

getfacl [-a | -d] {filename} {...}

where:

-a – Displays the file name, owner, group, and ACL entries of a file or directory
-d – Displays the file name, owner, group, and default ACL entries for a file or directory.

Setting ACLs

Display the setfacl manpage for command explanation:

setfacl [-bkndRLPvh] [{-m|-x} acl_spec] [{-M|-X} acl_file] file ...

The most common use for this command would be when copying or deleting ACLs, as described following.

Copying ACL from Another File

Copy an ACL from one file to another by piping getfacl output to setfacl:

getfacl {filename1} | setfacl -f - {filename2}

where {filename1} has the source ACL and {filename2} specifies the destination.

Deleting ACLs from a File

Delete ACL entries from a file or directory using setfacl:

setfacl -d acl-entry-list {filename} {...}