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When I was checking a machine set up by our sysadmin team, I encountered an completely empty fstab. In fact it was the default fstab installed by a debootstrap. 

# UNCONFIGURED FSTAB FOR BASE SYSTEM

I was going WTF first, but since the system is running for quite a while, I feel intrigued by this configuration. The system mounts seem to be fine:

sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,relatime)
proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)
udev on /dev type devtmpfs (rw,relatime,size=10240k,nr_inodes=4123203,mode=755)
devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000)
tmpfs on /run type tmpfs (rw,nosuid,noexec,relatime,size=3300328k,mode=755)
/dev/disk/by-uuid/477aa706-1737-4a08-8493-e617a58b8284 on / type ext4 (rw,relatime,data=ordered)
tmpfs on /run/lock type tmpfs (rw,nosuid,nodev,noexec,relatime,size=5120k)
tmpfs on /run/shm type tmpfs (rw,nosuid,nodev,noexec,relatime,size=6600640k)
rpc_pipefs on /var/lib/nfs/rpc_pipefs type rpc_pipefs (rw,relatime)
cgroup on /sys/fs/cgroup type tmpfs (rw,relatime,mode=755)
cgroup on /sys/fs/cgroup/cpuset type cgroup (rw,relatime,cpuset)
cgroup on /sys/fs/cgroup/cpu type cgroup (rw,relatime,cpu)
cgroup on /sys/fs/cgroup/cpuacct type cgroup (rw,relatime,cpuacct)
cgroup on /sys/fs/cgroup/devices type cgroup (rw,relatime,devices)
cgroup on /sys/fs/cgroup/freezer type cgroup (rw,relatime,freezer)
cgroup on /sys/fs/cgroup/net_cls type cgroup (rw,relatime,net_cls)
cgroup on /sys/fs/cgroup/blkio type cgroup (rw,relatime,blkio)
cgroup on /sys/fs/cgroup/perf_event type cgroup (rw,relatime,perf_event)
cgroup on /sys/fs/cgroup/net_prio type cgroup (rw,relatime,net_prio)

So my question is: Is this common practice and if not what side effects could arise from this configuration.

itsafire
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1 Answers1

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No, it's not a common practice at all.

Ask yourself this: "How do I know all the required filesystems are mounted?" Or better yet, ask yourself: "How would somebody else know all the required filesystems are mounted?" For example, it's not inconceivable there's a /var, /home, and so on that should be mounted, but isn't and you're writing directly to the mount points.

So while technically this system might be running without issues now, I think it's safe to say this violates some commonly accepted best practices.

Brandon Xavier
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  • Granted. You have no separated filesystems with this configuration. But you don't need to. In fact I know a lot of systems with only the root filesystem mount point in fstab. – itsafire Oct 03 '15 at 08:46