Linux
System
| Description | Command |
|---|---|
| Boot into CLI mode. | sudo systemctl set-default multi-user.target |
| Boot into desktop mode. | sudo systemctl set-default graphical.target |
SSH
| Description | Command |
|---|---|
| Create private/public SSH key file using 2048 bit encryption and with a comment. The command creates files under ~/.ssh folder. | ssh-keygen -b 2048 -C user@host.domain |
| Push public SSH key to a server | ssh-copy-id -p 41111 -i ~/.ssh/id_rsa.pub mhan@remote.server.com |
| Reset (SELinux) permissions related to SSH. This may be needed if all else fails to correct the issue of system not accepting public keys. | restorecon -R -v ~/.ssh |
Disk
Search
- xargs - to be processed - Things you (probably) didn’t know about xargs
LVM
Physical volume
| Description | Command |
|---|---|
| Initialize for use as LVM physical volume. | pvcreate /dev/sdb1 |
| Scanning for block devices. | lvmdiskscan |
| Display the physical volumes. | pvdisplay |
| Show all physical devices. | pvscan |
| Prevent allocation of physical extents on the free space of one or more physical volumes. | pvchange -x n /dev/sdb1 |
| Resize. | pvresize |
| Remove LVM label. | pvremove |
Volume group
| Description | Command |
|---|---|
| Create a volume group. | vgcreate vg1 /dev/sdb1 /dev/sdc1 |
| Add a physical volume to a volume group. | vgextend vg1 /dev/sdd1 |
| Display volume group. | vgdisplay new_vg |
| Scan disks for volume groups. | vgscan |
| Remove a physical volume from a volume group. | vgreduce group_name /dev/sdc1 |
| Change the maximum number of logical volumes of volume group vg00 to 128. | vgchange -l 128 /dev/vg00 |
| Activate or deactivate a volume group. | vgchange -a n my_volume_group |
| Remove a volume group. | vgremove officevg |
| Split the physical volumes of a volume group and create a new volume group. | $ vgsplit bigvg smallvg /dev/ram15 Volume group "smallvg" successfully split from "bigvg" |
| Merge the inactive volume group my_vg into the active or inactive volume group databases giving verbose runtime information. | vgmerge -v databases my_vg |
| Change the name of a volume group. | vgrename vg02 my_volume_group |
Users
UID or GID
| Description | Command |
|---|---|
| Check UID. | id -u username |
| Check GID. | id -g username |
| Check all of the groups a user belongs to. | id -G username |
| Check UID and all of the groups a user belongs to. | id username |
File
Permissions
| Letter | Number |
|---|---|
| r | 4 |
| w | 2 |
| x | 1 |
| rw- | 6 |
| r-x | 5 |
| rwx | 7 |
Audio
ALSA (Advanced Linux Sound Architecture)
Setting default output device
Ref: StackExchange/superuser: How to make Alsa pick a preferred sound device automatically?
List all audio cards you have:
$ cat /proc/asound/cards
0 [PCH ]: HDA-Intel - HDA Intel PCH
HDA Intel PCH at 0xf7530000 irq 41
1 [NVidia ]: HDA-Intel - HDA NVidia
HDA NVidia at 0xf7080000 irq 17
2 [SoundBar ]: USB-Audio - Dell AC511 USB SoundBar
Dell Dell AC511 USB SoundBar at usb-0000:00:14.0-4, full speed
Get ALSA identifiers of those:
$ aplay -l | awk -F \: '/,/{print $2}' | awk '{print $1}' | uniq
PCH
NVidia
SoundBar
Update /etc/asound.conf:
pcm.!default {
type hw
card SoundBar
}
ctl.!default {
type hw
card SoundBar
}
Miscellaneous
- X11 - X Window System
- i3wm - i3 window manager
- Running Steam on CentOS 7 with NVIDIA driver