10x Command

capture package and request interception

tcpdump -i ens192 -Xnns 0 port not 22 and tcp and not dst net 192.168
iptables -I OUTPUT -p tcp -d 13.250.94.254 -j REJECT

one-line

• alias
• dirs -v
• git shortlog -sn
• git status --ignore
• git check-ignore -v <file>
• journalctl -u shadowsocks-libev.service|xray.service -f
• nc -kl port could use as a http request log service
• curl -k insecure https

cron

• Command PATH, expand PATH=$PATH:other_path in crontab file first line (default is /usr/bin:/bin)
• Files permission, go settings->security set cron full disk access or specific folders

If cron job’s output(1|2) not redirect, it will mail to local(mail command check /var/mail/), omit mail(>/dev/null 2>&1), you could add MAILTO="someone@somewhere.com" in crontab file, this send mail to network mailbox

ln

Symlinks:

• When do path resolve, it assume itself as the source inode path
• have itself’s inode id
• unaccessible when source inode is deleted

Hard link:

• have the same inode number with the source file
• inode reference count +/- 1 when create/delete a hard link
• remove source file don’t influence hard link file
• directory can’t have hard link
• exa -lH show reference count field
• ls -i <filename>|choose 0|xargs find . -inum find all hard link reference

vpn

xray

bbr

/etc/sysctl.conf append two lines:

net.core.default_qdisc=fq
net.ipv4.tcp_congestion_control=bbr

reload: sysctl -p