I'm trying to detect what filesystems a kernel can support. Ideally in a little list of their names but I'll take anything you've got.
Note that I don't mean the current filesystems in use, just ones that the current kernel could, theoretically support directly (obviously, fuse could support infinite numbers more).
Can I list the filesystems a running kernel can support?
Well, answer /proc/filesystems is bluntly wrong — it reflects only those FSes that already were brought in use, but there are way more of them usually that kernel can support:
ls /lib/modules/$(uname -r)/kernel/fs
Another source is /proc/config.gz which might be absent in your distro (and I always wonder «why?!» in case), but a snapshot of config used to build the kernel typically can be found in the boot directory along with kernel and initrd images.
/boot/config-$(uname -r)
– Oli
Nov 03 '13 at 16:21
make menuconfig does...
– Oli
Nov 03 '13 at 16:24
/lib/modules/$(uname -r)/kernel/fs will only help with filesystems that have been enabled as modules, not ones that are built into the kernel. Additionally a module name might not match the filesystem name it provides, and a single module can provide multiple filesystems.
– phemmer
Nov 04 '13 at 01:42
/proc/config.gz which you seem to have overlooked in vain.
– poige
Nov 04 '13 at 04:16
/proc/config.gz at all. 1) it's not guaranteed to exist, 2) A module name might not match the filesystem name it provides, and a single module can provide multiple filesystems.
– phemmer
Nov 04 '13 at 12:00
/proc/filesystems lists all of the filesystem types supported by the running kernel, along with filesystem attributes, nodev to indicate that this filesystem is not backed by a block device, for example.
man 5 filesystems gives some more in-depth information.
cat /proc/filesystems lists a bunch of "nodev", obviously special-purpose filesystems, plus ext2, ext3, ext4. When I look in /lib/modules/3.11.6-1-ARCH/kernel/fs, I see a number of others, like "fats", "btrfs", "reiserfs" which are also regular on-disk filesystems, but don't appear in the /proc/filesystem list. What's up with that?
–
Nov 03 '13 at 14:49
nodev indicates that the filesystem in question is not a physical filesystem that needs a block device to live on, but rather a virtual filesystem that is backed by something other than a block device.
– Jonathan Callen
Nov 03 '13 at 14:49
/proc/filesystems only shows the filesystems that the kernel has loaded -- until you insert those modules into the kernel (which usually happens automatically when you need them), the kernel cannot support those filesystems.
– Jonathan Callen
Nov 03 '13 at 14:51
I believe this will give you what you want:
(cat /proc/filesystems | awk '{print $NF}' | sed '/^$/d'; ls -1 /lib/modules/$(uname -r)/kernel/fs) | sort -u
Explanation
Based on my best understanding:
cat /proc/filesystems | awk '{print $NF}' | sed '/^$/d' gives you all the filesystems that are natively supported by the kernel (like sysfs) along with those that have their kernel modules currently loadedls -1 /lib/modules/$(uname -r)/kernel/fs gives you the list of available filesystem modules available for your kernelsort -u sorts the combined results of the first two commands with duplicates removed (only show unique results -u)I am still learning linux, this works on Arch linux but I believe for at least ubuntu you may need to change the path /lib/modules/$(uname -r)/kernel/fs to a different directory appropriate for your distribution.
cat /proc/filesystems will show you which filesystems your running kernel can support right now.
ls /lib/modules/$(uname -r)/kernel/fs will provide clues as to which additional filesystems it could support, if you loaded the appropriate module.
The question has already been answered, but all of the other answers are in some way incomplete, misleading, untrue, or at least not true any more.
From man 8 mount (emphasis mine):
-t, --types fstype
The argument following the -t is used to indicate the filesystem type. The filesystem types which are currently supported depend on the running kernel. See /proc/filesystems and /lib/modules/$(uname -r)/kernel/fs for a complete list of the filesystems. The most common are ext2, ext3, ext4, xfs, btrfs, vfat, sysfs, proc, nfs and cifs.
I therefore can't fault anyone suggesting these approaches. However, as others have pointed out, the /lib/modules/$(uname -r)/kernel/fs directory contains filesystem-related kernel modules, which is not the same thing as currently supported filesystems:
The list can therefore contain additions, deletions and/or substitutions. It's not very reliable. It's possible to have a so-called "monolithic kernel" which has everything built-in already - in that (admittedly unusual) case the module list will be completely empty but the kernel will still support an arbitrary number of things - including, of course, various filesystems.
On the other hand, this is the contents of my /proc/filesystems file:
nodev sysfs
nodev tmpfs
nodev bdev
nodev proc
nodev cgroup
nodev cgroup2
nodev cpuset
nodev devtmpfs
nodev binfmt_misc
nodev configfs
nodev debugfs
nodev tracefs
nodev securityfs
nodev sockfs
nodev bpf
nodev pipefs
nodev ramfs
nodev hugetlbfs
nodev rpc_pipefs
nodev devpts
ext3
ext4
ext2
cramfs
squashfs
vfat
msdos
exfat
iso9660
nodev nfs
nodev nfs4
nodev nfsd
nodev cifs
nodev smb3
ntfs3
nodev autofs
fuseblk
nodev fuse
nodev fusectl
udf
f2fs
nodev efivarfs
nodev mqueue
nodev resctrl
btrfs
nodev pstore
There are filesystems in that list that my system has never even seen, let alone has currently mounted.
So on my system at least, that's the answer. I can't speak to why the currently accepted answer leads with the opposite conclusion; perhaps this is a new development...
cat /proc/filesystemsas pointed out in the kernel documentation. There may be modules, available on your hard drive, which support other additional filesystems, but that are not loaded into your running kernel. Those can be found in/lib/modules/$(uname -r)/kernel/fs. – Totor Nov 13 '21 at 23:25