[SOLVED] System shows "Low Disk Space" but "df -h" indicates it has space

skyworld_chen · 10-26-2019, 07:40 AM

Hi,
when I start my CentOS 7 through VMware workstation, I got message on "Low Disk Space". But when I run "df -h", I got these responds:

Code:

user02@localhost ~]$ df -h
Filesystem                    Size  Used Avail Use% Mounted on
/dev/sda3                     114G  114G  200K 100% /
devtmpfs                      5.9G     0  5.9G   0% /dev
tmpfs                         5.9G     0  5.9G   0% /dev/shm
tmpfs                         5.9G   13M  5.9G   1% /run
tmpfs                         5.9G     0  5.9G   0% /sys/fs/cgroup
/dev/sda1                     297M  271M   26M  92% /boot
/dev/mapper/vg_eda-home       100G  3.2G   97G   4% /home
/dev/mapper/vg_eda-tools_eda  147G   82G   66G  56% /tools_eda
.host:/                       531G  429G  102G  81% /mnt/hgfs
tmpfs                         1.2G   24K  1.2G   1% /run/user/1002

I'm quite confused because the /tools_eda and /home can provide more than 100G space. The /tools_eda and /home is the space I added through lvm, as figure below shows:

Code:

vgdisplay -v
  --- Volume group ---
  VG Name               vg_eda
  System ID             
  Format                lvm2
  Metadata Areas        2
  Metadata Sequence No  11
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                2
  Open LV               2
  Max PV                0
  Cur PV                2
  Act PV                2
  VG Size               479.99 GiB
  PE Size               4.00 MiB
  Total PE              122878
  Alloc PE / Size       122878 / 479.99 GiB
  Free  PE / Size       0 / 0   
  VG UUID               iKdogw-Am6E-Ip1z-6J5q-F7sD-Urcl-bVc3LR
   
  --- Logical volume ---
  LV Path                /dev/vg_eda/home
  LV Name                home
  VG Name                vg_eda
  LV UUID                FRwAjR-SVjT-a3Yn-0S4s-HVBa-CokG-1j0XMB
  LV Write Access        read/write
  LV Creation host, time localhost.localdomain, 2017-09-22 22:50:23 +0800
  LV Status              available
  # open                 1
  LV Size                100.00 GiB
  Current LE             25600
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:0
   
  --- Logical volume ---
  LV Path                /dev/vg_eda/tools_eda
  LV Name                tools_eda
  VG Name                vg_eda
  LV UUID                7PQokA-Mv8D-07cf-elvo-0hvu-d0tG-YQKfVN
  LV Write Access        read/write
  LV Creation host, time localhost.localdomain, 2017-09-24 14:19:35 +0800
  LV Status              available
  # open                 1
  LV Size                379.99 GiB
  Current LE             97278
  Segments               2
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:1
   
  --- Physical volumes ---
  PV Name               /dev/sdb1     
  PV UUID               u8SDhd-ThMT-X3X7-Xix0-I0G6-bJna-toz88m
  PV Status             allocatable
  Total PE / Free PE    63999 / 0
   
  PV Name               /dev/sda4     
  PV UUID               zp8KVw-sHKq-jnY4-dvAZ-ztxI-lsxb-hQxSX2
  PV Status             allocatable
  Total PE / Free PE    58879 / 0

Code:

lvdisplay
  --- Logical volume ---
  LV Path                /dev/vg_eda/home
  LV Name                home
  VG Name                vg_eda
  LV UUID                FRwAjR-SVjT-a3Yn-0S4s-HVBa-CokG-1j0XMB
  LV Write Access        read/write
  LV Creation host, time localhost.localdomain, 2017-09-22 22:50:23 +0800
  LV Status              available
  # open                 1
  LV Size                100.00 GiB
  Current LE             25600
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:0
   
  --- Logical volume ---
  LV Path                /dev/vg_eda/tools_eda
  LV Name                tools_eda
  VG Name                vg_eda
  LV UUID                7PQokA-Mv8D-07cf-elvo-0hvu-d0tG-YQKfVN
  LV Write Access        read/write
  LV Creation host, time localhost.localdomain, 2017-09-24 14:19:35 +0800
  LV Status              available
  # open                 1
  LV Size                379.99 GiB
  Current LE             97278
  Segments               2
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:1

Is there anything I did wrong?

scasey · 10-26-2019, 09:33 AM

Quote:

Originally Posted by skyworld_chen

Hi,
when I start my CentOS 7 through VMware workstation, I got message on "Low Disk Space". But when I run "df -h", I got these responds:

Code:

user02@localhost ~]$ df -h
Filesystem                    Size  Used Avail Use% Mounted on
/dev/sda3                     114G  114G  200K 100% /
.snip.

The root space is full. In my experience, that’s most often caused by an unmanaged log file in /var/log

teckk · 10-26-2019, 09:34 AM

/(root) is full

Code:

/dev/sda3                     114G  114G  200K 100% /

/boot has 26M free

Code:

/dev/sda1                     297M  271M   26M  92% /boot

$HOME has 97 GB free

Code:

/dev/mapper/vg_eda-home       100G  3.2G   97G   4% /home

skyworld_chen · 10-26-2019, 09:48 AM

thanks for kind reply. What confused me is that even though /root is full, there is still spare space for the disk, as /home and /tools_eda shows (I was told lvm could be used for such case), why system reports disk full? what is the relationship between /root and other directories?

scasey · 10-26-2019, 09:55 AM

Quote:

Originally Posted by skyworld_chen

thanks for kind reply. What confused me is that even though /root is full, there is still spare space for the disk, as /home and /tools_eda shows (I was told lvm could be used for such case), why system reports disk full? what is the relationship between /root and other directories?

root is where everything except /boot, /home and /tool-era live. So /bin, /user, /etc, /var, etc. Basically that’s where the OS is.

Lysander666 · 10-26-2019, 10:02 AM

Your / partition is extremely important and, as scasey says, is where your OS is. If it is full, you're going to run into a whole host of problems, including not being able to log into your desktop when you reboot. Yes, your entire disk is not full, but /, your most important partition is, and unless you clear some stuff, your whole disk may as well be full since you won't be able to use your OS properly.

Your / partition is currently 114GB full, which is crazy. It shouldn't even really be a quarter that full. You're going to have to do some research into some serious cleaning.

scasey · 10-26-2019, 10:21 AM

For comparison. root partitions on my headless server:

Code:

/dev/mapper/centos-root   50G  8.4G   42G  17% /

And on this desktop:

Code:

/dev/sda3        50G  8.5G   39G  19% /

Both are CentOS 7 installs on 500GB drives.

michaelk · 10-26-2019, 10:24 AM

In addition,

Code:

Filesystem                    Size  Used Avail Use% Mounted on
/dev/sda3                     114G  114G  200K 100% /
/dev/sda1                     297M  271M   26M  92% /boot
/dev/mapper/vg_eda-home       100G  3.2G   97G   4% /home
/dev/mapper/vg_eda-tools_eda  147G   82G   66G  56% /tools_eda

In a nutshell filesystems are separate spaces from each other. LVM makes it easier to enlarge a filesystem and merge more then one partition or disk into a single volume group/logical volume. However, /(root) is not part of a LVM and just adding a volume group does not add space to the root partition. If /(root) contains data that can be easily moved to /tools_eda that would free up space.

Without knowing how the virtual drive sda is partitioned or what type of filesystems they use I will assume they are xfs by default. You can not shrink xfs filesystems and therefore you can not easily move space from /home to /.

Lysander666 · 10-26-2019, 10:26 AM

Quote:

Originally Posted by scasey

For comparison. root partitions on my headless server...

And for further comparison for the OP, root sizes from my desktop:

Code:

/dev/sdc1        30G   27G  959M  97% /

And my main laptop:

Code:

/dev/root        30G   28G  760M  98% /

Both running Slackware.

Soon I'm going to have to do a little cleaning myself.

skyworld_chen · 10-26-2019, 07:52 PM

thanks for all of your kind reply. I guess what you mean is that "/" is similar to windows system "C:" while other directories, like /eda_tools or /home, etc is similar to other disk "D:" or "E:", ..., right? The "C:" is full while other disk still have space.

scasey · 10-26-2019, 09:07 PM

Quote:

Originally Posted by skyworld_chen

thanks for all of your kind reply. I guess what you mean is that "/" is similar to windows system "C:" while other directories, like /eda_tools or /home, etc is similar to other disk "D:" or "E:", ..., right? The "C:" is full while other disk still have space.

Sortof...but use "partition" rather than "disk" A disk can contain more than one partition. Yours has several. But I think you're getting the concept, and I'm just nit-picking the words you're using.

Yes, if a partition is full, then you'll get warnings/errors. If the root partition is full, your computer may not be able to start.

skyworld_chen · 10-27-2019, 04:31 AM

got it. Thanks very much

JeremyBoden · 11-20-2019, 10:36 AM

I don't think you've quite got it.

In Windows the C: drive is often allocated as 95% - or bigger.

Linux usually divides the disk into several partitions which cannot easily be resized on the fly.

So for example you can fill / whilst /home has loads of free space - if / and /home correspond to different partitions.
There are good reasons for this slight added complexity - your system programs and your data are kept separate, which makes data backups much easier.