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Tag Archives: Linux
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