I've had Raspberry Pi running few years Arch Linux ARM 24/7. All the sudden there seems to be inability to write anything, can't create new files nor edit anything, even as root. Same applies to any software, Nginx refuses to start. For example, when opening some file, say with nano there is a following textbox in the bottom:
[ Read 121 lines. (Warning: No write permission) ]
Reboot doesn't help, although it is possible to read the files,has the SD-card given up the ghost?
df -h
Filesystem Size Used Avail Use% Mounted on
/dev/root 29G 11G 16G 41% /
devtmpfs 237M 0 237M 0% /dev
tmpfs 241M 0 241M 0% /dev/shm
tmpfs 241M 4.3M 236M 2% /run
tmpfs 241M 0 241M 0% /sys/fs/cgroup
tmpfs 241M 0 241M 0% /tmp
/dev/mmcblk0p5 90M 22M 69M 24% /boot
tmpfs 49M 0 49M 0% /run/user/1000
touch testfile
touch: cannot touch ‘testfile’: Read-only file system
cat /etc/mtab
rootfs / rootfs rw 0 0
/dev/root / ext4 ro,relatime,data=ordered 0 0
devtmpfs /dev devtmpfs rw,relatime,size=241728k,nr_inodes=60432,mode=755 0 0
sysfs /sys sysfs rw,nosuid,nodev,noexec,relatime 0 0
proc /proc proc rw,nosuid,nodev,noexec,relatime 0 0
securityfs /sys/kernel/security securityfs rw,nosuid,nodev,noexec,relatime 0 0
tmpfs /dev/shm tmpfs rw,nosuid,nodev 0 0
devpts /dev/pts devpts rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000 0 0
tmpfs /run tmpfs rw,nosuid,nodev,mode=755 0 0
tmpfs /sys/fs/cgroup tmpfs ro,nosuid,nodev,noexec,mode=755 0 0
cgroup /sys/fs/cgroup/systemd cgroup rw,nosuid,nodev,noexec,relatime,xattr,release_agent=/usr/lib/systemd/systemd-cgroups-agent,name=systemd 0 0
cgroup /sys/fs/cgroup/cpu,cpuacct cgroup rw,nosuid,nodev,noexec,relatime,cpu,cpuacct 0 0
cgroup /sys/fs/cgroup/cpuset cgroup rw,nosuid,nodev,noexec,relatime,cpuset 0 0
cgroup /sys/fs/cgroup/freezer cgroup rw,nosuid,nodev,noexec,relatime,freezer 0 0
cgroup /sys/fs/cgroup/devices cgroup rw,nosuid,nodev,noexec,relatime,devices 0 0
cgroup /sys/fs/cgroup/perf_event cgroup rw,nosuid,nodev,noexec,relatime,perf_event 0 0
cgroup /sys/fs/cgroup/net_cls,net_prio cgroup rw,nosuid,nodev,noexec,relatime,net_cls,net_prio 0 0
cgroup /sys/fs/cgroup/blkio cgroup rw,nosuid,nodev,noexec,relatime,blkio 0 0
cgroup /sys/fs/cgroup/bfqio cgroup rw,nosuid,nodev,noexec,relatime,bfqio 0 0
systemd-1 /proc/sys/fs/binfmt_misc autofs rw,relatime,fd=28,pgrp=1,timeout=300,minproto=5,maxproto=5,direct 0 0
debugfs /sys/kernel/debug debugfs rw,relatime 0 0
tmpfs /tmp tmpfs rw 0 0
mqueue /dev/mqueue mqueue rw,relatime 0 0
configfs /sys/kernel/config configfs rw,relatime 0 0
/dev/mmcblk0p5 /boot vfat rw,noatime,fmask=0022,dmask=0022,codepage=437,iocharset=ascii,shortname=mixed,errors=remount-ro 0 0
tmpfs /run/user/1000 tmpfs rw,nosuid,nodev,relatime,size=49196k,mode=700,uid=1000,gid=100 0 0
sudo mount -f -o remount,rw /dev/mmcblk0p2
. I don't think there's anything wrong with the SD card; something else has gotten screwed up somehow. If you are running this headless and logging in remotely, plug in a monitor to watch it boot and see if anything is unusual. You could also look through the logs at the boot process and see if there's any clues/warnings there.