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For example, if I run:

sudo dumpe2fs /dev/sda1

I get detailed information about the partition.

I'm confused about this part, Lifetime writes, returns the following for my boot partition:

Lifetime writes:          12 kB

What does this 12 Kb mean?

This is full output:

user@root:/data$ sudo dumpe2fs /dev/sdb1
dumpe2fs 1.42.9 (4-Feb-2014)
Filesystem volume name:   <none>
Last mounted on:          <not available>
Filesystem UUID:          5524d5a6-4635-48a6-8cd9-a636e3ad2b2c
Filesystem magic number:  0xEF53
Filesystem revision #:    1 (dynamic)
Filesystem features:      ext_attr resize_inode dir_index filetype sparse_super large_file
Filesystem flags:         signed_directory_hash 
Default mount options:    user_xattr acl
Filesystem state:         clean
Errors behavior:          Continue
Filesystem OS type:       Linux
Inode count:              121680
Block count:              486144
Reserved block count:     0
Free blocks:              477783
Free inodes:              121669
First block:              0
Block size:               4096
Fragment size:            4096
Reserved GDT blocks:      118
Blocks per group:         32768
Fragments per group:      32768
Inodes per group:         8112
Inode blocks per group:   507
Filesystem created:       Thu Mar 27 03:18:09 2014
Last mount time:          Thu Mar 27 03:18:34 2014
Last write time:          Thu Mar 27 03:18:56 2014
Mount count:              1
Maximum mount count:      -1
Last checked:             Thu Mar 27 03:18:09 2014
Check interval:           0 (<none>)
Lifetime writes:          12 kB
Reserved blocks uid:      0 (user root)
Reserved blocks gid:      0 (group root)
First inode:              11
Inode size:           256
Required extra isize:     28
Desired extra isize:      28
Default directory hash:   half_md4
Directory Hash Seed:      8f43123d-1451-4047-a26c-d5227fd80240
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2 Answers 2

up vote 3 down vote accepted

Is all the writes in Bytes that the partition has since it's creation. In your case only 12kB has been written since the creation of the partition. Remember that the information could be wrong or obsolete in mounted file systems.

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Great you for explained. –  Marin Sagovac Mar 27 at 2:52
    
But why is wrong? This partition is boot partition and didn't takes 12 kB of space. –  Marin Sagovac Mar 27 at 2:52
2  
@MarinSagovac it is a blanket statement about relying on output from dumpe2fs on a mounted filesystem. This field in particular though should be accurate and you can query it in realtime through sysfs as I mention in my answer. –  casey Mar 27 at 2:54
    
Thank you for explanation. –  Marin Sagovac Mar 27 at 2:55
    
is there a limit to that lifetime write ? can it "roll over" ? or will it change to a scientific notation for bigger numbers? –  Olivier Dulac Mar 27 at 9:10

According to the ext4 manual this is the total number of bytes written to the filesystem since it was created. You can also query this value in kB by examing this file in the sysfs:

/sys/fs/ext4/<DEVICE>/lifetime_write_kbytes 
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