- Bash:
$(pwd)
- fish:
(pwd)
- Windows Command Line (
cmd
):%cd%
- PowerShell:
$(PWD)
(Case-insensitive)
Tag: Linux
-
Current Working Directory for Different OS and Tools
-
Zip/Unzip Multi-volume Archives from Command Line
Compress with level 0 means no compression, split then into 500 MB per slice.
zip -0 -s 500m InstallESD InstallESD.dmg
To merge/unzip them:
zip -FF InstallESD.zip --out InstallESD-full.zip
-
Run Process in Background and Redirect Output to a Log – The Ease Way
$ some_cmd > some_cmd.log 2>&1 &
Source: https://unix.stackexchange.com/a/106641
-
Mount EBS Volumes To EC2 Linux Instances
View all available volumes:
$ lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT xvda 202:0 0 10G 0 disk ├─xvda1 202:1 0 1M 0 part └─xvda2 202:2 0 10G 0 part / xvdf 202:80 0 3.9T 0 disk
$ file -s /dev/xvdf /dev/xvdf: data
If returns
data
it means the volume is empty. We need to format it first:$ mkfs -t ext4 /dev/xvdf mke2fs 1.42.9 (28-Dec-2013) Filesystem label= OS type: Linux Block size=4096 (log=2) Fragment size=4096 (log=2) Stride=0 blocks, Stripe width=0 blocks 262144000 inodes, 1048576000 blocks 52428800 blocks (5.00%) reserved for the super user First data block=0 Maximum filesystem blocks=3196059648 32000 block groups 32768 blocks per group, 32768 fragments per group 8192 inodes per group Superblock backups stored on blocks: 32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, 4096000, 7962624, 11239424, 20480000, 23887872, 71663616, 78675968, 102400000, 214990848, 512000000, 550731776, 644972544 Allocating group tables: done Writing inode tables: done Creating journal (32768 blocks): done Writing superblocks and filesystem accounting information: done
Create a new directory and mount it to EBS volume:
$ cd / && mkdir ebs-data $ mount /dev/xvdf /ebs-data/
Check volume mount:
$ df -h Filesystem Size Used Avail Use% Mounted on /dev/xvda2 10G 878M 9.2G 9% / devtmpfs 476M 0 476M 0% /dev tmpfs 496M 0 496M 0% /dev/shm tmpfs 496M 13M 483M 3% /run tmpfs 496M 0 496M 0% /sys/fs/cgroup tmpfs 100M 0 100M 0% /run/user/1000 tmpfs 100M 0 100M 0% /run/user/0 /dev/xvdf 3.9T 89M 3.7T 1% /ebs-data
In order to make it mount automatically after each reboot, we need to edit
/etc/fstab
, first make a backup:$ cp /etc/fstab /etc/fstab.orig
Find the UUID for the volume you need to mount:
$ ls -al /dev/disk/by-uuid/ total 0 drwxr-xr-x. 2 root root 80 Nov 25 05:04 . drwxr-xr-x. 4 root root 80 Nov 25 04:40 .. lrwxrwxrwx. 1 root root 11 Nov 25 04:40 de4dfe96-23df-4bb9-ad5e-08472e7d1866 -> ../../xvda2 lrwxrwxrwx. 1 root root 10 Nov 25 05:04 e54af798-14df-419d-aeb7-bd1b4d583886 -> ../../xvdf
Then edit
/etc/fstab
:$ vi /etc/fstab
with:
# # /etc/fstab # Created by anaconda on Tue Jul 11 15:57:39 2017 # # Accessible filesystems, by reference, are maintained under '/dev/disk' # See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info # UUID=de4dfe96-23df-4bb9-ad5e-08472e7d1866 / xfs defaults 0 0 UUID=e54af798-14df-419d-aeb7-bd1b4d583886 /ebs-data ext4 defaults,nofail 0 2
Check if
fstab
has any error:$ mount -a
-
Use cURL to view request headers
curl -v -s -o - -X OPTIONS https://www.google.com/
-
List and Change Kernel in CentOS 7
List kernels:
$ egrep ^menuentry /etc/grub2.cfg | cut -f 2 -d \' CentOS Linux (3.10.0-327.10.1.el7.x86_64) 7 (Core) CentOS Linux (3.10.0-327.4.5.el7.x86_64) 7 (Core) CentOS Linux (3.10.0-327.3.1.el7.x86_64) 7 (Core) CentOS Linux (3.10.0-229.20.1.el7.x86_64) 7 (Core) CentOS Linux (3.10.0-123.9.3.el7.x86_64) 7 (Core) CentOS Linux, with Linux 0-rescue-45461f76679f48ee96e95da6cc798cc8
Set kernel to the fourth:
$ grub2-set-default 3
-
Shaving your RTT with TCP Fast Open – Bradley Falzon
Check out the recently released RFC on TCP Fast Open, a spec that allows most TCP connections to send data during the initial SYN packet – reducing the initial round trips required from 2 to 1. Excellent for HTTPS connections.
Source: Shaving your RTT with TCP Fast Open – Bradley Falzon