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I have three main partitions on my disc /dev/sda:

/dev/sda1            2048   117186559    58592256   83  Linux
/dev/sda2       117186560   128905215     5859328   82  Linux swap / Solaris
/dev/sda3   *   128905216   324216831    97655808    7  HPFS/NTFS/exFAT
/dev/sda4       324216832  1250263039   463023104    b  W95 FAT32

/dev/sda3 is a Windows 7 partition and /dev/sda4 is a FAT32 partition where I keep my data. My problem is that yesterday I can't write on /dev/sda4 and when I tried to change the file permissions I get an error:

$ sudo chmod 777 /media/fourat/74A7-A44E/
chmod: changing permissions of ‘74A7-A44E/’: Read-only file system

mount output:

/dev/sda1 on / type ext4 (rw,errors=remount-ro)
proc on /proc type proc (rw,noexec,nosuid,nodev)
sysfs on /sys type sysfs (rw,noexec,nosuid,nodev)
none on /sys/fs/cgroup type tmpfs (rw)
none on /sys/fs/fuse/connections type fusectl (rw)
none on /sys/kernel/debug type debugfs (rw)
none on /sys/kernel/security type securityfs (rw)
udev on /dev type devtmpfs (rw,mode=0755)
devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620)
tmpfs on /run type tmpfs (rw,noexec,nosuid,size=10%,mode=0755)
none on /run/lock type tmpfs (rw,noexec,nosuid,nodev,size=5242880)
none on /run/shm type tmpfs (rw,nosuid,nodev)
none on /run/user type tmpfs (rw,noexec,nosuid,nodev,size=104857600,mode=0755)
none on /sys/fs/pstore type pstore (rw)
systemd on /sys/fs/cgroup/systemd type cgroup (rw,noexec,nosuid,nodev,none,name=systemd)
gvfsd-fuse on /run/user/1000/gvfs type fuse.gvfsd-fuse (rw,nosuid,nodev,user=fourat)
/dev/sda4 on /media/fourat/74A7-A44E type vfat (rw,nosuid,nodev,uid=1000,gid=1000,shortname=mixed,dmask=0077,utf8=1,showexec,flush,uhelper=udisks2)

Solved: Remounted the partition as instructed in mikewhatever's comment with

sudo mount -o remount,rw /dev/sda4
  • There's nothing in your question that shows us the location of '74A7-A44E'. Please update your question with the output of mount and where the directory you cannot change permissions of actually is. – Marcin Kaminski Jan 11 '15 at 19:05
  • Are you trying to apply chmod command on a file that exists on USB? – Wolverine Jan 11 '15 at 19:15
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    If a filesystem is read only, you need to re-mount it as rw - sudo mount -o remount,rw /dev/sda4, and not hammer it with chmod. The cause of such errors is usually filesystem corruption, so you'll need to check it for errors in Windows. – mikewhatever Jan 11 '15 at 19:17
  • If I'm not mistaken, FAT partitions don't have 'permissions'. Instead of chmod, you could just give your user permission to access the files with mount/fstab. – earthmeLon Jan 12 '15 at 18:37
  • 7
    Possible duplicate of How to make read-only file system writable? – Zanna Mar 7 '17 at 7:14

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