Linux general tips
Forcing ext3 to check next boot
To force ext3
fsck checking in boot time, say in
/, add the
# touch /forcefsck
Easy way to force or disable fsck at boot time with Debian?
Changing keyboard layout at console
To load keyboard layout at console, just use the command::
# loadkeys <keymap>
Keymaps can be found in keymaps. To change to ABNT2 layout, for instance, type::
# loadkeys br-abnt2
Enabling core dumped on Linux
By default, AFAIK, Linux doesn't create core files when a program suffers core dumped. To enable them, let your shell know that it is allowed to create core files which size is greater than zero. For example, in bash::
$ ulimit -c 2000000
A Linux FAQ entry
The default behaviour is to create a core file named
core. But it can yield
problems if more than one process is core dumped (they will generate the same
core file name, and the first will overwrite the later).
To change the default name, change the
kernel.core_pattern option in
sysctl. For example, to make it generate core files like in BSD
# sysctl kernel.core_pattern='%e.core'
Also see the sysctl documentation to get a full description of this option:
Making filesystem in file
To make a filesystem in a file, like if it were a partition, just follow the following commands.
First, create the file::
$ dd if=/dev/zero of=/tmp/ext2.fs bs=4096 count=$(echo '1024 * 50' | bc)
Then, format it::
$ mkfs.ext2 /tmp/ext2.fs
Finally, mount it as root::
$ sudo mount -o loop /tmp/ext2.fs <mount_point>
Find which package contains a file in Debian and derivated
$ dpkg -S filename_pattern
Find which package contains a file in Debian Linux
Change default locale and encoding in Ubuntu
Ubuntu, by default, comes with en_US.UTF-8 enabled by default, only, in the installation with the English language. If you want to enable other locales/encodings, follow these steps:
1. Append the locale and encoding you want to
2. Change the default locale and encoding in
/etc/default/locale, e. g.:
3. Run, as root::
# locale-gen --purge
Where does GNOME mounts devices?
GNOME (in GNU/Linux distributions like Ubuntu) mounts automatically devices
such as USB sticks and remote filesystems. But the
mount option does not
show the mouting point. This is because it uses
gvfs-mount to mount
devices. By default, GNOME uses the directory in
~/.gvfs, that do not
Mount NetBSD partitions under Linux
how to mount ffs partition under linux
First, verify if
ufs module is loaded::
# lsmod | grep ufs
If not, load it. It was necessary under the Ubunbu live CD we are using in this case::
# modprobe ufs
Then, you will able to see NetBSD partitions with the following command::
# sfdisk -l
The output of this command, in my computer, is::
Disk /dev/sda: 60801 cylinders, 255 heads, 63 sectors/track Units = cylinders of 8225280 bytes, blocks of 1024 bytes, counting from 0 Device Boot Start End #cyls #blocks Id System /dev/sda1 * 0+ 31870 31871- 256003776 a9 NetBSD /dev/sda2 0 - 0 0 0 Empty /dev/sda3 0 - 0 0 0 Empty /dev/sda4 0 - 0 0 0 Empty /dev/sda5 0+ 7648- 7649- 61440120 /dev/sda6 7648+ 8158- 510- 4096008 /dev/sda7 8158+ 8224- 66- 524664 /dev/sda8 8224+ 15873- 7649- 61439584+ /dev/sda9 15873+ 18422- 2550- 20480040 /dev/sda10 18422+ 31870 13449- 108023359+
See that it lists the NetBSD slice as
sda1. NetBSD partitions are
sda6 is swap.
Finally, to mount it, use the following command::
# mount -t ufs -o ro,ufstype=44bsd /dev/sda5 /mnt/sda5
Change Ubuntu DNS servers
Using Ubuntu GNU/Linux 22.04.1 LTS.
2. Locate the part regarding nameservers addresses and edit them. Save and close the file.
netplan apply command.
Change DNS server in Ubuntu Command Line
Error: Failed to download metadata for repo 'remi-modular'
(Using Rocky Linux 9.2, but it may also be valid for CentOS, AlmaLinux or RedHat).
On Rocky Linux, if you are having this problem when trying to install a
dnf module with
dnf module install php:remi-8.0, maybe you should first
# dnf module reset php
List content of a given package in CentOS, RockyLinux and AlmaLinux
To list the content of a given installed package, i.e., what files it installs, run:
$ rpm -qi --filebypkg packagename