[solved] Low filesystem root message

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jlehtone
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Re: Low filesystem root message

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

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

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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"

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$ 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:

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$ 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

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/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:

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

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trevor14smith
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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

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TrevorH
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Re: Low filesystem root message

Post by TrevorH » 2020/06/30 20:55:37

Post the output from fdisk -lu /dev/sd[a-z]
The future appears to be RHEL or Debian. I think I'm going Debian.
Info for USB installs on http://wiki.centos.org/HowTos/InstallFromUSBkey
CentOS 5 and 6 are deadest, do not use them.
Use the FAQ Luke

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trevor14smith
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Re: Low filesystem root message

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

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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

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TrevorH
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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.
The future appears to be RHEL or Debian. I think I'm going Debian.
Info for USB installs on http://wiki.centos.org/HowTos/InstallFromUSBkey
CentOS 5 and 6 are deadest, do not use them.
Use the FAQ Luke

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jlehtone
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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?

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trevor14smith
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Re: Low filesystem root message

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

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

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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

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TrevorH
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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!
The future appears to be RHEL or Debian. I think I'm going Debian.
Info for USB installs on http://wiki.centos.org/HowTos/InstallFromUSBkey
CentOS 5 and 6 are deadest, do not use them.
Use the FAQ Luke

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trevor14smith
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Re: [solved] Low filesystem root message

Post by trevor14smith » 2020/12/23 13:29:19

Just realised that what I did did not have 100% the finished result:
Created a new PV /dev sda4 then did the following

vgextend centosVG /dev/sda4
lvextend -L +10G /dev/mapper/centosVG-root

When I do df -Th it appears that I did not exand the filesystem correctly - Any advise to fix this?

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Filesystem                Type      Size  Used Avail Use% Mounted on
devtmpfs                  devtmpfs  7.7G     0  7.7G   0% /dev
tmpfs                     tmpfs     7.8G  6.4M  7.8G   1% /dev/shm
tmpfs                     tmpfs     7.8G   11M  7.8G   1% /run
tmpfs                     tmpfs     7.8G     0  7.8G   0% /sys/fs/cgroup
/dev/mapper/centosVG-root ext4      9.1G  8.1G  502M  95% /
/dev/sda2                 ext4      453M  381M   45M  90% /boot
/dev/sda1                 vfat      476M   12M  465M   3% /boot/efi
/dev/mapper/centosVG-home ext4       92G   70G   18G  80% /home
/dev/mapper/centosVG-var  ext4      9.1G  3.0G  5.7G  35% /var
However lsblk shows:

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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  19.3G  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
└─sda4              8:4    0   1.7T  0 part 
  └─centosVG-root 253:0    0  19.3G  0 lvm  /
Thanks

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TrevorH
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Re: [solved] Low filesystem root message

Post by TrevorH » 2020/12/23 13:46:49

lvextend -L +10G /dev/mapper/centosVG-root
You missed the -r switch to tell it to extend the filesystem on the device at the same time. Now you will need to do that manually using either resize2fs or xfs_growfs depending on which filesystem type is in use.
The future appears to be RHEL or Debian. I think I'm going Debian.
Info for USB installs on http://wiki.centos.org/HowTos/InstallFromUSBkey
CentOS 5 and 6 are deadest, do not use them.
Use the FAQ Luke

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