[solved] Low filesystem root message

General support questions
User avatar
jlehtone
Posts: 2870
Joined: 2007/12/11 08:17:33
Location: Finland

Re: Low filesystem root message

Post by jlehtone » 2020/06/30 14:56:48

trevor14smith wrote:
2020/06/30 10:58:09

Code: Select all

Filesystem                Type      Size  Used Avail Use% Mounted on
/dev/mapper/centosVG-root ext4      9.1G  8.6G   50M 100% /
/dev/sda2                 ext4      453M  376M   50M  89% /boot
/dev/sda1                 vfat      476M   12M  465M   3% /boot/efi
/dev/mapper/centosVG-var  ext4      9.1G  2.4G  6.2G  28% /var
/dev/mapper/centosVG-home ext4       92G   70G   18G  81% /home
Did I allocate enough root space when installing?
"Full" means, no, not enough.

How much is enough depends on the purpose: what software and data has to be there.
Two examples. First a server that runs one service. No GUI. The /usr is "small"

Code: Select all

$ sudo du -m -x -d 1 /
1	/root
34	/etc
340	/opt
1	/media
1	/mnt
1	/home
1361	/usr
1	/tmp
1	/lost+found
1	/srv
250	/var
119	/boot
2103	/
Then a GUI desktop with applications for a user. The /usr + /opt is close to 14 GB:

Code: Select all

$ sudo du -m -x -d 1 /
458	/boot
6	/root
829	/var
47	/etc
736	/opt
12684	/usr
1	/media
1	/srv
1	/lost+found
1	/mnt
14757	/
trevor14smith wrote:
2020/06/30 10:58:09

Code: Select all

/dev/mapper/centosVG-var  ext4      9.1G  2.4G  6.2G  28% /var
Note. Red Hat does not recommend mounting the /var from separate filesystem. Essential things get mounted under /var early in boot and therefore /var has to be mounted really early too.

It is fine to mount subdirectories (/var/xxx) from separate filesystems, for example http, ftp, sql, or docker data, for those services start much later.


The /tmp holds temporary files. There can be lots, so having it on the root partition is a risk.
There is a way to have /tmp in RAM too; it will be completely cleaned on every reboot.
A file in /tmp is safe to remove if no process needs it any more. However, well-behaving processes would remove temporaries when they end, so files there may well be in use.


You have one saving grace: ext4. CentOS's default filesystem is xfs, which cannot be shrunk. Ext4 can be resized smaller.
It is thus possible to shrink /var and /home and give / more. However, like Trevor pointed out, you don't have much to play with.


PS. Other information gathering commands:

Code: Select all

lsblk
blkid
findmnt
(The findmnt tends to tell something even when the others get stuck on misbehaving mounts.)

User avatar
trevor14smith
Posts: 31
Joined: 2017/02/25 16:51:35
Contact:

Re: Low filesystem root message

Post by trevor14smith » 2020/06/30 20:54:45

Thanks for all the replies:
Deleting the unused stuff in /tmp did help and I do not get the warning message now.
This is a desktop..the spec when I bought it said 256GB SSD + 1TB HDD..never did see how to access the HDD

User avatar
TrevorH
Forum Moderator
Posts: 28836
Joined: 2009/09/24 10:40:56
Location: Brighton, UK

Re: Low filesystem root message

Post by TrevorH » 2020/06/30 20:55:37

Post the output from fdisk -lu /dev/sd[a-z]
CentOS 6 will die in November 2020 - migrate sooner rather than later!
Info for USB installs on http://wiki.centos.org/HowTos/InstallFromUSBkey
CentOS 5 is dead, do not use it.
Full time Geek, part time moderator. Use the FAQ Luke

User avatar
trevor14smith
Posts: 31
Joined: 2017/02/25 16:51:35
Contact:

Re: Low filesystem root message

Post by trevor14smith » 2020/06/30 21:09:11

Code: Select all

fdisk -lu /dev/sd[a-z]
WARNING: fdisk GPT support is currently new, and therefore in an experimental phase. Use at your own discretion.

Disk /dev/sda: 2000.4 GB, 2000398934016 bytes, 3907029168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: gpt
Disk identifier: 0175F5AF-F590-47B7-AA8A-23D787838126


#         Start          End    Size  Type            Name
 1         2048       976895    476M  EFI System      EFI System Partition
 2       976896      1951743    476M  Microsoft basic 
 3      1951744    251971583  119.2G  Linux LVM       
fdisk: cannot open /dev/sdb: No medium found

Disk /dev/sdc: 500.1 GB, 500107862016 bytes, 976773168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0xcb4a53fb

   Device Boot      Start         End      Blocks   Id  System
/dev/sdc1   *          63   976768064   488384001   83  Linux

User avatar
TrevorH
Forum Moderator
Posts: 28836
Joined: 2009/09/24 10:40:56
Location: Brighton, UK

Re: Low filesystem root message

Post by TrevorH » 2020/07/01 00:10:46

According to that you have 2 disks, one of 2TB and the other 500GB.

On the 2TB drive you have two 476MB partitions, one is /boot and the other /boot/efi. Then you have another partition that's 119GB in size and the rest of the 2TB is unpartitioned and unused. The 119GB partition is the LVM physical volume that's used for your 'centosVG' Volume Group. You have plenty of space on this disk that you can use for your system.

On your 500GB disk, you have a single partition occupying all the available space. However I see no mention of /dev/sdc1 in your df output so I cannot tell if it is used or if it is entirely empty. I suspect this is your SSD but I am not sure you are using it. Perhaps running file -s /dev/sdc1 might tell you something useful. You'll want to find out what is on this as your system will be much quicker if it's SSD based.
CentOS 6 will die in November 2020 - migrate sooner rather than later!
Info for USB installs on http://wiki.centos.org/HowTos/InstallFromUSBkey
CentOS 5 is dead, do not use it.
Full time Geek, part time moderator. Use the FAQ Luke

User avatar
jlehtone
Posts: 2870
Joined: 2007/12/11 08:17:33
Location: Finland

Re: Low filesystem root message

Post by jlehtone » 2020/07/01 05:50:38

trevor14smith wrote:
2020/06/30 10:58:09
/dev/sdc1 ext2 459G 214G 222G 50% /run/media/trevor/FEDORA
I see the sdc, but what is it, really?

User avatar
trevor14smith
Posts: 31
Joined: 2017/02/25 16:51:35
Contact:

Re: Low filesystem root message

Post by trevor14smith » 2020/07/01 10:58:49

sdc is my 500G external hard drive for backups..

Code: Select all

lsblk
NAME        MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda           8:0    0   1.8T  0 disk 
├─sda1        8:1    0   476M  0 part /boot/efi
├─sda2        8:2    0   476M  0 part /boot
└─sda3        8:3    0 119.2G  0 part 
  ├─centosVG-root
            253:0    0   9.3G  0 lvm  /
  ├─centosVG-swap
            253:1    0   7.5G  0 lvm  [SWAP]
  ├─centosVG-home
            253:2    0  93.1G  0 lvm  /home
  └─centosVG-var
            253:3    0   9.3G  0 lvm  /var
sdc           8:32   0 465.8G  0 disk 
└─sdc1        8:33   0 465.8G  0 part /run/media/trevor/FEDORA
loop0         7:0    0  57.9M  1 loop /var/lib/snapd/snap/hey-mail/2
loop1         7:1    0  62.3M  1 loop /var/lib/snapd/snap/hey-mail/3
loop2         7:2    0  62.1M  1 loop /var/lib/snapd/snap/gtk-common-themes/1506
loop3         7:3    0  29.8M  1 loop /var/lib/snapd/snap/snapd/8140
loop4         7:4    0    55M  1 loop /var/lib/snapd/snap/core18/1754
loop5         7:5    0 161.4M  1 loop /var/lib/snapd/snap/gnome-3-28-1804/128

User avatar
TrevorH
Forum Moderator
Posts: 28836
Joined: 2009/09/24 10:40:56
Location: Brighton, UK

Re: Low filesystem root message

Post by TrevorH » 2020/07/01 11:16:43

OK, so you do not have an SSD and a hard disk on this. You appear to only have a 2TB disk and are only using about 1/16th of it.

You have plenty of space available, you just need to tell your system to use it. The easy way to do that is to create a new partition on the 2TB drive, tag it as type LVM (0x8e) and save the changes then reboot. Once the reboot is done, you need to use pvcreate on the new partition to make it a new LVM PV then add that PV to your existing 'centosVG' volume group and then you can expand any of the filesystems that appear in your df output as being on /dev/mapper/centosVG-*. With ~1.75TB available, you should have enough to be going on with!
CentOS 6 will die in November 2020 - migrate sooner rather than later!
Info for USB installs on http://wiki.centos.org/HowTos/InstallFromUSBkey
CentOS 5 is dead, do not use it.
Full time Geek, part time moderator. Use the FAQ Luke

Post Reply

Return to “CentOS 7 - General Support”