Docs: Linux
Route DNS requests of a subdomain to a specific DNS server
Using systemd-resolved, you can create a file under /etc/systemd/resolved/resolved.conf.d/, call it custom.conf.
In this file, add the following:
[Resolve]
Domains=~<SUBDOMAIN>
DNS=<YOUR_DNS_SERVER_IP>
*.<SUBDOMAIN> to your server.Restart systemd-resolved service to reload the configuration:
Allow Discord to start without checking updates
Useful when the version in the package manager isn't yet up to date with the latest release. Add the following line in ~/.config/discord/settings.json:
Too many open files - Failed to initialize inotify
You can do an ad-hoc raise of the max_user_instances parameter:
- You can put a higher value than 256 if needed
You can also persist this configuration by adding a configuration file under /etc/sysctl.d/, call it custom.conf with the following line:
Force dark mode on GTK-3 applications in Gnome DE
Add the following line in your ~/.config/gtk-3.0/settings.ini file (or create it if it doesn't exist):
Select power usage profiles using TuneD
You can verify if TuneD is running via the command
You can check the available profiles (and the current one) in TuneD by running the command
To set a profile, use the following command (will require admin privilege)
Syscalls tracing
Note: strace prints its output to stderr to avoid mixing it with the output of the traced command, we need to forward that output to stdout
- Trace filesystem syscalls, replacing all file descriptors by file paths and grepping:
Extract text from a variable
$ TOTO=ref/tag/1.2.3
$ echo ${TOTO#ref/*/} # This pattern-matches the variable and extracts the remaining text
1.2.3
Resize (extend) disk
lsblk # find which disk you want to extend
growpart /dev/<DISK_NAME> <PARTIITON_NO>
resize2fs /dev/<DISK_NAME_PARTITION_NO>
Memory diagnosys tools
Miscellanous stuff noted from this video.
free:
# This is printed in mebibytes
~ free -h
total used free shared buff/cache available
Mem: 15Gi 2.9Gi 12Gi 15Mi 470Mi 12Gi
Swap: 4.0Gi 0B 4.0Gi
vmstat:
# Gives slightly more info compared to free
# Info about swap space, io and cpu load
~ vmstat
procs -----------memory---------- ---swap-- -----io---- -system-- -------cpu-------
r b swpd free buff cache si so bi bo in cs us sy id wa st gu
0 0 0 12775648 16132 465752 0 0 150 71 186 0 0 0 100 0 0 0
# Run vmstat 3 times every 2 seconds
~ vmstat 2 3
procs -----------memory---------- ---swap-- -----io---- -system-- -------cpu-------
r b swpd free buff cache si so bi bo in cs us sy id wa st gu
0 0 0 12767436 16812 465808 0 0 148 71 197 0 0 0 100 0 0 0
0 0 0 12768672 16820 465800 0 0 0 212 656 1491 0 0 99 0 0 0
0 0 0 12765212 16820 465808 0 0 0 60 709 1608 0 0 100 0 0 0
ps:
# Shows all the processes, users running them and extended informations
# Some fields:
# - VSZ: virtual memory size, virtual memory allocated but not necessary all of it is used
# - RSS: resident set size, an estimate of the amount of the physical memory used by a process. This is an estimate as shared libraries are counted for each process, even though they may be loaded only once.
~ ps aux
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 1 0.0 0.0 22404 13492 ? Ss 18:53 0:00 /sbin/init
root 2 0.0 0.0 2616 1444 ? Sl 18:53 0:00 /init
[...]
top:
Press 1 to print info about all cores load.
Interesting fields for memory are VIRT (vm), RES (RSS), SHR (shared memory).
swapon: