Nextcloud notes

LOG file location

By default, a log file named nextcloud.log will be created in the directory which has been configured by the datadirectory parameter in config/config.php.

LOG file clear
truncate /nextcloud.log --size 0
Maintenance mode
sudo -u www-data php occ maintenance:mode --on
sudo -u www-data php occ maintenance:mode --off
Empty the trashbin

Maintenance mode mode be off.

sudo -u www-data php occ trashbin:cleanup <user1> <user2> ... <userN>
sudo -u www-data php occ trashbin:cleanup --all-users

Disable IPv6 on Raspberry Pi3+

To disable IPv6 and avoid the module loaded in memory just edit /etc/modprobe.d/ipv6.conf:

alias net-pf-10 off
alias ipv6 off
options ipv6 disable_ipv6=1
blacklist ipv6

ChibiOS “undefined reference to `_sbrk'” linker error

If we get this linker error with ChibiOS:

/usr/bin/../lib/gcc/arm-none-eabi/7.3.1/../../../../arm-none-eabi/lib/thumb/v6-m/libg.a(lib_a-sbrkr.o): In function `_sbrk_r':
sbrkr.c:(.text._sbrk_r+0xc): undefined reference to `_sbrk'
collect2: error: ld returned 1 exit status

we simply need to add syscalls.c to be compiled, add the following to CSRC in the Makefile:


We should underline that _sbrk will work correctly if and only if CH_CFG_USE_MEMCORE == TRUE (editable in chconf.h). Else, malloc() will always return 0 and result in an errno of ENOMEM.

Find machine/host names on the network

Firstly we try to resolve the PTR records in DNS for the specified IP addresses.
It sends nothing to the hosts so there is no guarantee if it is really connected or turned on but we can get the actual DNS map including those devices which are within their DHCP lease timeout.

nmap -sn -sL

Then we scan for hosts really connected sending ARP requests. The disadvantage is that it only works on your subnet.

nmap -sP

or if we want to remove useless lines:

nmap -sP | grep -E "([0-9]{1,3}[\.]){3}[0-9]{1,3}"

output example:

cesare@cesare-desktop:~$ nmap -sP | grep -E "([0-9]{1,3}[\.]){3}[0-9]{1,3}"
 Nmap scan report for router (
 Nmap scan report for vpnudp (
 Nmap scan report for vpntcp (
 Nmap scan report for desktop (
 Nmap scan report for unas (
 Nmap scan report for pi2 (
 Nmap scan report for cloud (

or for a better output:

nmap -sP | grep -E "([0-9]{1,3}[\.]){3}[0-9]{1,3}" | cut -d ' ' -f5-
router (
vpnudp (
vpntcp (
desktop (
unas (
cloud (

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