Troubleshoot Linux boot failures from /etc/fstab errors -

Incorrect entries in /etc/fstab can prevent a Linux ECS instance from booting. Fix or remove invalid mount entries to restore normal startup.

Note

Expand the following section for details about the /etc/fstab file fields.

fstab file

#
# /etc/fstab
# Created by anaconda on Fri Jun 28 04:16:23 2024
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#<file system>                                 <dir>   <type>  <options>       <dump> <pass>
UUID=c8b5b2da-55xxx07573e22  /               ext4    defaults        1       1

Fields in the fstab file:

file system: the UUID of the file system to mount, in UUID=xxxx-xxxx format.
dir: the mount point.
type: the file system type, such as ext4 and xfs.

options: mount options, typically defaults. Separate multiple options with commas (,). Common mount options:

Mount option	Description
defaults	Uses default mount settings. For an Ext4 file system, equivalent to `rw,suid,dev,exec,auto,nouser,async`.
rw	Mounts the file system in read/write mode.
ro	Mounts the file system in read-only mode.
auto	Automatically mounts the file system at boot or when `mount -a` runs.
noauto	Mounts the file system only when explicitly mounted by command.
suid	Allows SUID operations and sets the SGID bit, enabling temporary privilege escalation for specific tasks.
nosuid	Denies SUID operations and does not set the SGID bit.
dev	Parses the block device on which the file system resides.
nodev	Does not parse the block device on which the file system resides.
exec	Allows executing files on the mount point.
noexec	Prevents executing files on the mount point.
nouser	Only the root user can mount the file system.
async	Enables asynchronous I/O.
sync	Enables synchronous I/O.
nofail	Ignores missing devices at boot to prevent startup failures.

dump: used by the dump utility. 0 = no backup, 1 = back up the file system.
pass: used by fsck to set the check order. Typically 1 for the root file system, 2 or higher for others, and 0 to skip checking.

Causes

The fstab file was not updated before detaching or re-initializing a cloud disk, leaving stale mount entries.
The device name or UUID is incorrect.
The file system type is incorrect.
One or more mount options have invalid values.

Solution

Connect to the Linux instance with VNC. See Connect to an instance by using VNC.

Note
The system enters emergency mode when this issue occurs. Enter the root password to log on.
Back up the /etc/fstab file:
```
cp /etc/fstab /etc/fstab.bak
```

View the mount information of all disks, including partition names, file system types, and mount points:

df -Th

[root@iZxxxq8Z ~]# df -Th
Filesystem      Type      Size  Used Avail Use% Mounted on
devtmpfs        devtmpfs  868M     0  868M   0% /dev
tmpfs           tmpfs     879M     0  879M   0% /dev/shm
tmpfs           tmpfs     879M  496K  878M   1% /run
tmpfs           tmpfs     879M     0  879M   0% /sys/fs/cgroup
/dev/vda1       ext4       40G  2.2G   36G   6% /
tmpfs           tmpfs     176M     0  176M   0% /run/user/0
/dev/vdb1       ext4       30G   45M   28G   1% /mnt
/dev/vdb2       ext4      9.8G   37M  9.2G   1% /tmp

View the auto-mount entries in /etc/fstab:

cat /etc/fstab

[root@iZ2xxxgq8Z ~]# cat /etc/fstab
#
# /etc/fstab
# Created by anaconda on Fri Jun 28 04:16:23 2024
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
UUID=c8b5b2da-5xxx8b07573e22 /                       ext4    defaults        1 1
UUID=f77303eb-4xxx77378b9ce1 /mnt ext4 defaults 0 0
UUID=c40c6d63-7xxx3ea8df22d7 /tmp ext4 defaults 0 0

Compare the /etc/fstab entries with the output from Step 3. Delete any redundant or invalid lines.
(Optional) To auto-mount disk partitions not shown in Step 3, see Configure UUIDs in the fstab file to automatically mount data disks.
Restart the instance:
```
reboot
```