Linux Archives - Redino blog

lnav is a great log file viewer. To use its latest features, we need to fetch the source code and compile manually.
When compiling lnav using make, following error is appeared

listview_curses.cc: In member function ‘virtual void listview_curses::do_update()’:
listview_curses.cc:293:76: error: ‘mvwin_wchnstr’ was not declared in this scope
             mvwin_wchnstr(this->lv_window, y, this->lv_x, row_ch, width - 1);
                                                                            ^
listview_curses.cc:297:77: error: ‘mvwadd_wchnstr’ was not declared in this scope
             mvwadd_wchnstr(this->lv_window, y, this->lv_x, row_ch, width - 1);

listview_curses.cc: In member function ‘virtual void listview_curses::do_update()’:

listview_curses.cc:293:76: error: ‘mvwin_wchnstr’ was not declared in this scope

mvwin_wchnstr(this->lv_window, y, this->lv_x, row_ch, width - 1);

listview_curses.cc:297:77: error: ‘mvwadd_wchnstr’ was not declared in this scope

mvwadd_wchnstr(this->lv_window, y, this->lv_x, row_ch, width - 1);

I have installed all requirements stated in documentation.

Solution

The lnav documentation only said ncurses library is needed, but not mention which version.
My current installed ncurses library is libncurses5-dev. Changing to libncursesw5-dev fixed this issue.

apt install libncursesw5-dev

1	apt install libncursesw5-dev

(This command is for apt package manager, please change to corresponding command according to the package manager you use.)

I created a new user called phone for the client, and created a new directory /home/phone as his home directory. Next create some files for testing purpose.

cd /home/phone
touch a b c

1 2	cd /home/phone touch a b c

Then modify /etc/ssh/sshd_config to set chroot configuration

Match User phone
    ForceCommand internal-sftp
    ChrootDirectory /home/phone

Match User phone

ForceCommand internal-sftp

ChrootDirectory /home/phone

But logging in with this new user and run ls command, no files are listed, it returns nothing.. But if I run ls in ssh, the files are shown.

root@iZbp14uomoa9zt7kqaxumcZ:/home/phone# ls
a  b  c

1 2	root@iZbp14uomoa9zt7kqaxumcZ:/home/phone# ls a b c

After trying lots of time, the reason is found: It's because there is no "x" permission for /home/phone directory..

root@iZbp14uomoa9zt7kqaxumcZ:~# ls -lh /home
drw-r--r-- 3 root root 4.0K Sep  3 11:34 phone

1 2	root@iZbp14uomoa9zt7kqaxumcZ:~# ls -lh /home drw-r--r-- 3 root root 4.0K Sep 3 11:34 phone

What is "x" permission?

The "x" permission for directory is used to traverse directory. And the "x" permission for file is for file execution.

Then run following command to add "x" permission for /home/phone

chmod 744 /home/phone

1	chmod 744 /home/phone

And try running ls command in sftp again, the issue is fixed now, we can see files are listed now.

My cloud server moved to VPC from classic network just now, and connecting to it via SSH got following error

Connecting to upay...
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!
It is also possible that the RSA host key has just been changed.
The fingerprint for the RSA key sent by the remote host is
91:65:8c:eb:63:86:5f:f2:b0:e6:77:d2:81:71:ef:2a.
Please contact your system administrator.
Add correct host key in /root/.ssh/known_hosts to get rid of this message.
Offending key in /root/.ssh/known_hosts:1
RSA host key for x.x.x.x has changed and you have requested strict checking.
Host key verification failed.
Couldn't read packet: Connection reset by peer

Connecting to upay...

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@

@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@

IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!

Someone could be eavesdropping on you right now (man-in-the-middle attack)!

It is also possible that the RSA host key has just been changed.

The fingerprint for the RSA key sent by the remote host is

91:65:8c:eb:63:86:5f:f2:b0:e6:77:d2:81:71:ef:2a.

Please contact your system administrator.

Add correct host key in /root/.ssh/known_hosts to get rid of this message.

Offending key in /root/.ssh/known_hosts:1

RSA host key for x.x.x.x has changed and you have requested strict checking.

Host key verification failed.

Couldn't read packet: Connection reset by peer

Solution

It seems the server host key is changed, one way to solve this prolem is to remove the line containing server IP address from /root/.ssh/known_hosts . Then connect to it by SSH again, it will ask you whether trust this new host key, like following message

Connecting to upay...
The authenticity of host 'x.x.x.x (x.x.x.x)' can't be established.
RSA key fingerprint is 91:65:8c:eb:63:86:5f:f2:b0:e6:77:d2:81:71:ef:2a.
Are you sure you want to continue connecting (yes/no)?

Connecting to upay...

The authenticity of host 'x.x.x.x (x.x.x.x)' can't be established.

RSA key fingerprint is 91:65:8c:eb:63:86:5f:f2:b0:e6:77:d2:81:71:ef:2a.

Are you sure you want to continue connecting (yes/no)?

Type yes and press Enter key, this new host key is added to .ssh/known_hosts then.

Also you can obtain the host key from the remote server, and add it to .ssh/known_hosts manually , but we won't cover this method in detail.

The gitlab execution on our company internal server eats lots of memory, the server has 32G memory, and gitlab took more than half of it.

ps aux|sort -k4

1	ps aux\|sort -k4

I found there are lots of unicorn processes running, and each unicorn process is taking 1.5% memory

In top command output it's displaying as ruby process and took nearly 500MB resident memory (by default top is sorting by cpu usage, pressing < or > key to change sorting column)

ps aux|grep unicorn|wc -l

1	ps aux\|grep unicorn\|wc -l

Running above command outputs 34, that means at most 34 unicorn processes are running (some other processes' name also contain unicorn)..

Assume there are 30 real unicorn process running, each takes 500MB memory, then they will take 30*500MB=15GB memory

To decrease unicorn processes count, edit /etc/gitlab/gitlab.rb, and uncomment following line

#unicorn['worker_processes'] = 2

1	#unicorn['worker_processes'] = 2

Next restart GitLab

gitlab-ctl restart

1	gitlab-ctl restart

Now the memory usage is decreased.

(Note that running gitlab-ctl reconfigure will not kill already running unicorn processes)

Netcat is one utility in NMap toolset, it maybe named as nc, ncat or netcat on different Linux distributions. (It's ncat on CentOS 6).

On CentOS 6 netcat is not installed by default, to install it we can run following command

yum install nmap

1	yum install nmap

Then run following command to check netcat is installed correctly

ncat -v

ncat -v

First run passwd command to change the password, after inputting new password, following output is shown.

passwd: password updated successfully

I bind docker port 22 to host port 33333, then running following command to connect to it using ssh with the new password we set earlier

ssh -p 33333 root@localhost

1	ssh -p 33333 root@localhost

After inputing password, following error is appeared

Permission denied, please try again.

SSH logs from /var/log/auth.log

May 16 08:52:19 789c53cf55d3 sshd[132]: Set /proc/self/oom_score_adj from 0 to -1000
May 16 08:52:19 789c53cf55d3 sshd[132]: debug1: Bind to port 22 on 0.0.0.0.
May 16 08:52:19 789c53cf55d3 sshd[132]: Server listening on 0.0.0.0 port 22.
May 16 08:52:19 789c53cf55d3 sshd[132]: debug1: Bind to port 22 on ::.
May 16 08:52:19 789c53cf55d3 sshd[132]: Server listening on :: port 22.
May 16 08:52:26 789c53cf55d3 sshd[132]: debug1: Forked child 133.
May 16 08:52:26 789c53cf55d3 sshd[133]: Set /proc/self/oom_score_adj to 0
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: rexec start in 5 out 5 newsock 5 pipe 7 sock 8
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: inetd sockets after dupping: 3, 3
May 16 08:52:26 789c53cf55d3 sshd[133]: Connection from 172.17.42.1 port 34162 on 172.17.0.25 port 22
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: Client protocol version 2.0; client software version OpenSSH_5.3
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: match: OpenSSH_5.3 pat OpenSSH_5* compat 0x0c000000
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: Enabling compatibility mode for protocol 2.0
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: Local version string SSH-2.0-OpenSSH_6.6.1p1 Ubuntu-2ubuntu2.10
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: list_hostkey_types: ssh-rsa,ssh-dss,ecdsa-sha2-nistp256,ssh-ed25519
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: SSH2_MSG_KEXINIT sent
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: SSH2_MSG_KEXINIT received
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: kex: client->server aes128-ctr hmac-sha1 none
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: kex: server->client aes128-ctr hmac-sha1 none
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: SSH2_MSG_KEX_DH_GEX_REQUEST received
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: SSH2_MSG_KEX_DH_GEX_GROUP sent
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: expecting SSH2_MSG_KEX_DH_GEX_INIT
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: SSH2_MSG_KEX_DH_GEX_REPLY sent
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: SSH2_MSG_NEWKEYS sent
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: expecting SSH2_MSG_NEWKEYS
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: SSH2_MSG_NEWKEYS received
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: KEX done
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: userauth-request for user root service ssh-connection method none
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: attempt 0 failures 0
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: PAM: initializing for "root"
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: PAM: setting PAM_RHOST to "172.17.42.1"
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: PAM: setting PAM_TTY to "ssh"
May 16 08:52:26 789c53cf55d3 sshd[133]: Failed none for root from 172.17.42.1 port 34162 ssh2
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: userauth-request for user root service ssh-connection method publickey
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: attempt 1 failures 0
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: test whether pkalg/pkblob are acceptable
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: temporarily_use_uid: 0/0 (e=0/0)
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: trying public key file /root/.ssh/authorized_keys
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: Could not open authorized keys '/root/.ssh/authorized_keys': No such file or directory
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: restore_uid: 0/0
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: temporarily_use_uid: 0/0 (e=0/0)
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: trying public key file /root/.ssh/authorized_keys2
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: Could not open authorized keys '/root/.ssh/authorized_keys2': No such file or directory
May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: restore_uid: 0/0
May 16 08:52:26 789c53cf55d3 sshd[133]: Failed publickey for root from 172.17.42.1 port 34162 ssh2
May 16 08:52:28 789c53cf55d3 sshd[133]: debug1: userauth-request for user root service ssh-connection method password
May 16 08:52:28 789c53cf55d3 sshd[133]: debug1: attempt 2 failures 1
May 16 08:52:28 789c53cf55d3 sshd[133]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=172.17.42.1  user=root
May 16 08:52:29 789c53cf55d3 sshd[133]: debug1: PAM: password authentication failed for root: Authentication failure
May 16 08:52:29 789c53cf55d3 sshd[133]: Failed password for root from 172.17.42.1 port 34162 ssh2

May 16 08:52:19 789c53cf55d3 sshd[132]: Set /proc/self/oom_score_adj from 0 to -1000

May 16 08:52:19 789c53cf55d3 sshd[132]: debug1: Bind to port 22 on 0.0.0.0.

May 16 08:52:19 789c53cf55d3 sshd[132]: Server listening on 0.0.0.0 port 22.

May 16 08:52:19 789c53cf55d3 sshd[132]: debug1: Bind to port 22 on ::.

May 16 08:52:19 789c53cf55d3 sshd[132]: Server listening on :: port 22.

May 16 08:52:26 789c53cf55d3 sshd[132]: debug1: Forked child 133.

May 16 08:52:26 789c53cf55d3 sshd[133]: Set /proc/self/oom_score_adj to 0

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: rexec start in 5 out 5 newsock 5 pipe 7 sock 8

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: inetd sockets after dupping: 3, 3

May 16 08:52:26 789c53cf55d3 sshd[133]: Connection from 172.17.42.1 port 34162 on 172.17.0.25 port 22

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: Client protocol version 2.0; client software version OpenSSH_5.3

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: match: OpenSSH_5.3 pat OpenSSH_5* compat 0x0c000000

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: Enabling compatibility mode for protocol 2.0

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: Local version string SSH-2.0-OpenSSH_6.6.1p1 Ubuntu-2ubuntu2.10

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: list_hostkey_types: ssh-rsa,ssh-dss,ecdsa-sha2-nistp256,ssh-ed25519

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: SSH2_MSG_KEXINIT sent

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: SSH2_MSG_KEXINIT received

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: kex: client->server aes128-ctr hmac-sha1 none

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: kex: server->client aes128-ctr hmac-sha1 none

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: SSH2_MSG_KEX_DH_GEX_REQUEST received

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: SSH2_MSG_KEX_DH_GEX_GROUP sent

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: expecting SSH2_MSG_KEX_DH_GEX_INIT

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: SSH2_MSG_KEX_DH_GEX_REPLY sent

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: SSH2_MSG_NEWKEYS sent

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: expecting SSH2_MSG_NEWKEYS

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: SSH2_MSG_NEWKEYS received

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: KEX done

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: userauth-request for user root service ssh-connection method none

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: attempt 0 failures 0

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: PAM: initializing for "root"

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: PAM: setting PAM_RHOST to "172.17.42.1"

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: PAM: setting PAM_TTY to "ssh"

May 16 08:52:26 789c53cf55d3 sshd[133]: Failed none for root from 172.17.42.1 port 34162 ssh2

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: userauth-request for user root service ssh-connection method publickey

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: attempt 1 failures 0

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: test whether pkalg/pkblob are acceptable

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: temporarily_use_uid: 0/0 (e=0/0)

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: trying public key file /root/.ssh/authorized_keys

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: Could not open authorized keys '/root/.ssh/authorized_keys': No such file or directory

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: restore_uid: 0/0

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: temporarily_use_uid: 0/0 (e=0/0)

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: trying public key file /root/.ssh/authorized_keys2

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: Could not open authorized keys '/root/.ssh/authorized_keys2': No such file or directory

May 16 08:52:26 789c53cf55d3 sshd[133]: debug1: restore_uid: 0/0

May 16 08:52:26 789c53cf55d3 sshd[133]: Failed publickey for root from 172.17.42.1 port 34162 ssh2

May 16 08:52:28 789c53cf55d3 sshd[133]: debug1: userauth-request for user root service ssh-connection method password

May 16 08:52:28 789c53cf55d3 sshd[133]: debug1: attempt 2 failures 1

May 16 08:52:28 789c53cf55d3 sshd[133]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=172.17.42.1 user=root

May 16 08:52:29 789c53cf55d3 sshd[133]: debug1: PAM: password authentication failed for root: Authentication failure

May 16 08:52:29 789c53cf55d3 sshd[133]: Failed password for root from 172.17.42.1 port 34162 ssh2

Solution

To fix this issue, change /etc/ssh/sshd_config

PermitRootLogin without-password

1	PermitRootLogin without-password

PermitRootLogin yes

1	PermitRootLogin yes

Restart sshd and connect to it again, it should work now.

Linux

‘mvwin_wchnstr’ was not declared in this scope when compiling lnav

Solution

SFTP ls command returns no files

What is "x" permission?

SSH WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!

Solution

GitLab took too much memory

CentOS 6 Install netcat

Docker SSH set password not working

Solution