Miscellaneous¶
In this chapter we discuss miscellaneous aspects related to or about BackupPC-Clone.
Ext4 Filesystem and Inodes¶
The ext4 filesystem is still one of the most used filesystems. One of the properties of the ext4 filesystem is that the number of inodes is fixed and can not be increased later. BackupPC requires relatively a lot of inodes due to fact it is using many hardlinks to the same file.
When creating an ext4 filesystem for a clone make sure that this filesystem has enough inodes. One can compare the number of inodes with the following commands:
tune2fs -l `df /var/lib/BackupPC | awk '{if (NR==2) print $1}'` | grep -i 'inode count'
tune2fs -l `df /var/lib/BackupPC-Clone | awk '{if (NR==2) print $1}'` | grep -i 'inode count'
The -i
, -I
, and -N
option of mke2fs
impact the number of inodes created.
Clone on Removable Media¶
When creating a clone on removable media it is recommended to encrypt the filesystem such that in case of loss or theft your data is still safe.
Suppose your external disk is available under /dev/sdh1
you can encrypt your external disk with the following
commands:
cryptsetup --verify-passphrase --cipher aes-cbc-essiv:sha256 --key-size 256 luksFormat /dev/sdh1
cryptsetup luksOpen /dev/sdh1 sdh1-luks
The encrypted disk will be available at /dev/mapper/sdh1-luks
.
We found no noticeable performance impact when using disk encryption
Reserved blocks¶
When using a dedicated partition (and an ext4 filesystem) for the clone you might set the percentage of the filesystem
blocks reserved for the super-user to 0 using the -m
option of the mke2fs
command.
Example Creating Filesystem for Clone¶
In this section we give an example how to create a filesystem for a clone of BackupPC.
cryptsetup --verify-passphrase --cipher aes-cbc-essiv:sha256 --key-size 256 luksFormat /dev/sdh1
cryptsetup luksOpen /dev/sdh1 sdh1-luks
mke2fs -t ext4 -i 16384 -m 0 /dev/mapper/sdh1-luks
mkdir /var/lib/BackupPC-Clone
mount -t ext4 /dev/mapper/sdh1-luks /var/lib/BackupPC-Clone
chown backuppc.backuppc /var/lib/BackupPC-Clone
See Clone on Removable Media for more information about the cryptsetup commands, see Ext4 Filesystem and Inodes and
Reserved blocks for more information on the -i
and -m
options of the mke2fs
command.
Verifying a Clone Backup¶
A backup is paramount for your company regardless of its size and you should not trust BackupPC-Clone blindly.
You can verify BackupPC-Clone has created a correct clone of a host backup simply with the following command (replace
host
and num
with the actual hostname and backup number):
diff --recursive --brief /var/lib/BackupPC/pc/host/num/ /var/lib/BackupPC-Clone/clone/pc/host/num/
You can ignore the following message:
Only in /var/lib/BackupPC/pc/host/num/: backuppc-clone.csv